| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * linux/ipc/sem.c |
| * Copyright (C) 1992 Krishna Balasubramanian |
| * Copyright (C) 1995 Eric Schenk, Bruno Haible |
| * |
| * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com> |
| * |
| * SMP-threaded, sysctl's added |
| * (c) 1999 Manfred Spraul <manfred@colorfullife.com> |
| * Enforced range limit on SEM_UNDO |
| * (c) 2001 Red Hat Inc |
| * Lockless wakeup |
| * (c) 2003 Manfred Spraul <manfred@colorfullife.com> |
| * (c) 2016 Davidlohr Bueso <dave@stgolabs.net> |
| * Further wakeup optimizations, documentation |
| * (c) 2010 Manfred Spraul <manfred@colorfullife.com> |
| * |
| * support for audit of ipc object properties and permission changes |
| * Dustin Kirkland <dustin.kirkland@us.ibm.com> |
| * |
| * namespaces support |
| * OpenVZ, SWsoft Inc. |
| * Pavel Emelianov <xemul@openvz.org> |
| * |
| * Implementation notes: (May 2010) |
| * This file implements System V semaphores. |
| * |
| * User space visible behavior: |
| * - FIFO ordering for semop() operations (just FIFO, not starvation |
| * protection) |
| * - multiple semaphore operations that alter the same semaphore in |
| * one semop() are handled. |
| * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and |
| * SETALL calls. |
| * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO. |
| * - undo adjustments at process exit are limited to 0..SEMVMX. |
| * - namespace are supported. |
| * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing |
| * to /proc/sys/kernel/sem. |
| * - statistics about the usage are reported in /proc/sysvipc/sem. |
| * |
| * Internals: |
| * - scalability: |
| * - all global variables are read-mostly. |
| * - semop() calls and semctl(RMID) are synchronized by RCU. |
| * - most operations do write operations (actually: spin_lock calls) to |
| * the per-semaphore array structure. |
| * Thus: Perfect SMP scaling between independent semaphore arrays. |
| * If multiple semaphores in one array are used, then cache line |
| * trashing on the semaphore array spinlock will limit the scaling. |
| * - semncnt and semzcnt are calculated on demand in count_semcnt() |
| * - the task that performs a successful semop() scans the list of all |
| * sleeping tasks and completes any pending operations that can be fulfilled. |
| * Semaphores are actively given to waiting tasks (necessary for FIFO). |
| * (see update_queue()) |
| * - To improve the scalability, the actual wake-up calls are performed after |
| * dropping all locks. (see wake_up_sem_queue_prepare()) |
| * - All work is done by the waker, the woken up task does not have to do |
| * anything - not even acquiring a lock or dropping a refcount. |
| * - A woken up task may not even touch the semaphore array anymore, it may |
| * have been destroyed already by a semctl(RMID). |
| * - UNDO values are stored in an array (one per process and per |
| * semaphore array, lazily allocated). For backwards compatibility, multiple |
| * modes for the UNDO variables are supported (per process, per thread) |
| * (see copy_semundo, CLONE_SYSVSEM) |
| * - There are two lists of the pending operations: a per-array list |
| * and per-semaphore list (stored in the array). This allows to achieve FIFO |
| * ordering without always scanning all pending operations. |
| * The worst-case behavior is nevertheless O(N^2) for N wakeups. |
| */ |
| |
| #include <linux/compat.h> |
| #include <linux/slab.h> |
| #include <linux/spinlock.h> |
| #include <linux/init.h> |
| #include <linux/proc_fs.h> |
| #include <linux/time.h> |
| #include <linux/security.h> |
| #include <linux/syscalls.h> |
| #include <linux/audit.h> |
| #include <linux/capability.h> |
| #include <linux/seq_file.h> |
| #include <linux/rwsem.h> |
| #include <linux/nsproxy.h> |
| #include <linux/ipc_namespace.h> |
| #include <linux/sched/wake_q.h> |
| #include <linux/nospec.h> |
| #include <linux/rhashtable.h> |
| |
| #include <linux/uaccess.h> |
| #include "util.h" |
| |
| /* One semaphore structure for each semaphore in the system. */ |
| struct sem { |
| int semval; /* current value */ |
| /* |
| * PID of the process that last modified the semaphore. For |
| * Linux, specifically these are: |
| * - semop |
| * - semctl, via SETVAL and SETALL. |
| * - at task exit when performing undo adjustments (see exit_sem). |
| */ |
| struct pid *sempid; |
| spinlock_t lock; /* spinlock for fine-grained semtimedop */ |
| struct list_head pending_alter; /* pending single-sop operations */ |
| /* that alter the semaphore */ |
| struct list_head pending_const; /* pending single-sop operations */ |
| /* that do not alter the semaphore*/ |
| time64_t sem_otime; /* candidate for sem_otime */ |
| } ____cacheline_aligned_in_smp; |
| |
| /* One sem_array data structure for each set of semaphores in the system. */ |
| struct sem_array { |
| struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */ |
| time64_t sem_ctime; /* create/last semctl() time */ |
| struct list_head pending_alter; /* pending operations */ |
| /* that alter the array */ |
| struct list_head pending_const; /* pending complex operations */ |
| /* that do not alter semvals */ |
| struct list_head list_id; /* undo requests on this array */ |
| int sem_nsems; /* no. of semaphores in array */ |
| int complex_count; /* pending complex operations */ |
| unsigned int use_global_lock;/* >0: global lock required */ |
| |
| struct sem sems[]; |
| } __randomize_layout; |
| |
| /* One queue for each sleeping process in the system. */ |
| struct sem_queue { |
| struct list_head list; /* queue of pending operations */ |
| struct task_struct *sleeper; /* this process */ |
| struct sem_undo *undo; /* undo structure */ |
| struct pid *pid; /* process id of requesting process */ |
| int status; /* completion status of operation */ |
| struct sembuf *sops; /* array of pending operations */ |
| struct sembuf *blocking; /* the operation that blocked */ |
| int nsops; /* number of operations */ |
| bool alter; /* does *sops alter the array? */ |
| bool dupsop; /* sops on more than one sem_num */ |
| }; |
| |
| /* Each task has a list of undo requests. They are executed automatically |
| * when the process exits. |
| */ |
| struct sem_undo { |
| struct list_head list_proc; /* per-process list: * |
| * all undos from one process |
| * rcu protected */ |
| struct rcu_head rcu; /* rcu struct for sem_undo */ |
| struct sem_undo_list *ulp; /* back ptr to sem_undo_list */ |
| struct list_head list_id; /* per semaphore array list: |
| * all undos for one array */ |
| int semid; /* semaphore set identifier */ |
| short *semadj; /* array of adjustments */ |
| /* one per semaphore */ |
| }; |
| |
| /* sem_undo_list controls shared access to the list of sem_undo structures |
| * that may be shared among all a CLONE_SYSVSEM task group. |
| */ |
| struct sem_undo_list { |
| refcount_t refcnt; |
| spinlock_t lock; |
| struct list_head list_proc; |
| }; |
| |
| |
| #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) |
| |
| static int newary(struct ipc_namespace *, struct ipc_params *); |
| static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); |
| #ifdef CONFIG_PROC_FS |
| static int sysvipc_sem_proc_show(struct seq_file *s, void *it); |
| #endif |
| |
| #define SEMMSL_FAST 256 /* 512 bytes on stack */ |
| #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ |
| |
| /* |
| * Switching from the mode suitable for simple ops |
| * to the mode for complex ops is costly. Therefore: |
| * use some hysteresis |
| */ |
| #define USE_GLOBAL_LOCK_HYSTERESIS 10 |
| |
| /* |
| * Locking: |
| * a) global sem_lock() for read/write |
| * sem_undo.id_next, |
| * sem_array.complex_count, |
| * sem_array.pending{_alter,_const}, |
| * sem_array.sem_undo |
| * |
| * b) global or semaphore sem_lock() for read/write: |
| * sem_array.sems[i].pending_{const,alter}: |
| * |
| * c) special: |
| * sem_undo_list.list_proc: |
| * * undo_list->lock for write |
| * * rcu for read |
| * use_global_lock: |
| * * global sem_lock() for write |
| * * either local or global sem_lock() for read. |
| * |
| * Memory ordering: |
| * Most ordering is enforced by using spin_lock() and spin_unlock(). |
| * The special case is use_global_lock: |
| * Setting it from non-zero to 0 is a RELEASE, this is ensured by |
| * using smp_store_release(). |
| * Testing if it is non-zero is an ACQUIRE, this is ensured by using |
| * smp_load_acquire(). |
| * Setting it from 0 to non-zero must be ordered with regards to |
| * this smp_load_acquire(), this is guaranteed because the smp_load_acquire() |
| * is inside a spin_lock() and after a write from 0 to non-zero a |
| * spin_lock()+spin_unlock() is done. |
| */ |
| |
| #define sc_semmsl sem_ctls[0] |
| #define sc_semmns sem_ctls[1] |
| #define sc_semopm sem_ctls[2] |
| #define sc_semmni sem_ctls[3] |
| |
| void sem_init_ns(struct ipc_namespace *ns) |
| { |
| ns->sc_semmsl = SEMMSL; |
| ns->sc_semmns = SEMMNS; |
| ns->sc_semopm = SEMOPM; |
| ns->sc_semmni = SEMMNI; |
| ns->used_sems = 0; |
| ipc_init_ids(&ns->ids[IPC_SEM_IDS]); |
| } |
| |
| #ifdef CONFIG_IPC_NS |
| void sem_exit_ns(struct ipc_namespace *ns) |
| { |
| free_ipcs(ns, &sem_ids(ns), freeary); |
| idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); |
| rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht); |
| } |
| #endif |
| |
| void __init sem_init(void) |
| { |
| sem_init_ns(&init_ipc_ns); |
| ipc_init_proc_interface("sysvipc/sem", |
| " key semid perms nsems uid gid cuid cgid otime ctime\n", |
| IPC_SEM_IDS, sysvipc_sem_proc_show); |
| } |
| |
| /** |
| * unmerge_queues - unmerge queues, if possible. |
| * @sma: semaphore array |
| * |
| * The function unmerges the wait queues if complex_count is 0. |
| * It must be called prior to dropping the global semaphore array lock. |
| */ |
| static void unmerge_queues(struct sem_array *sma) |
| { |
| struct sem_queue *q, *tq; |
| |
| /* complex operations still around? */ |
| if (sma->complex_count) |
| return; |
| /* |
| * We will switch back to simple mode. |
| * Move all pending operation back into the per-semaphore |
| * queues. |
| */ |
| list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
| struct sem *curr; |
| curr = &sma->sems[q->sops[0].sem_num]; |
| |
| list_add_tail(&q->list, &curr->pending_alter); |
| } |
| INIT_LIST_HEAD(&sma->pending_alter); |
| } |
| |
| /** |
| * merge_queues - merge single semop queues into global queue |
| * @sma: semaphore array |
| * |
| * This function merges all per-semaphore queues into the global queue. |
| * It is necessary to achieve FIFO ordering for the pending single-sop |
| * operations when a multi-semop operation must sleep. |
| * Only the alter operations must be moved, the const operations can stay. |
| */ |
| static void merge_queues(struct sem_array *sma) |
| { |
| int i; |
| for (i = 0; i < sma->sem_nsems; i++) { |
| struct sem *sem = &sma->sems[i]; |
| |
| list_splice_init(&sem->pending_alter, &sma->pending_alter); |
| } |
| } |
| |
| static void sem_rcu_free(struct rcu_head *head) |
| { |
| struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu); |
| struct sem_array *sma = container_of(p, struct sem_array, sem_perm); |
| |
| security_sem_free(&sma->sem_perm); |
| kvfree(sma); |
| } |
| |
| /* |
| * Enter the mode suitable for non-simple operations: |
| * Caller must own sem_perm.lock. |
| */ |
| static void complexmode_enter(struct sem_array *sma) |
| { |
| int i; |
| struct sem *sem; |
| |
| if (sma->use_global_lock > 0) { |
| /* |
| * We are already in global lock mode. |
| * Nothing to do, just reset the |
| * counter until we return to simple mode. |
| */ |
| sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; |
| return; |
| } |
| sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; |
| |
| for (i = 0; i < sma->sem_nsems; i++) { |
| sem = &sma->sems[i]; |
| spin_lock(&sem->lock); |
| spin_unlock(&sem->lock); |
| } |
| } |
| |
| /* |
| * Try to leave the mode that disallows simple operations: |
| * Caller must own sem_perm.lock. |
| */ |
| static void complexmode_tryleave(struct sem_array *sma) |
| { |
| if (sma->complex_count) { |
| /* Complex ops are sleeping. |
| * We must stay in complex mode |
| */ |
| return; |
| } |
| if (sma->use_global_lock == 1) { |
| /* |
| * Immediately after setting use_global_lock to 0, |
| * a simple op can start. Thus: all memory writes |
| * performed by the current operation must be visible |
| * before we set use_global_lock to 0. |
| */ |
| smp_store_release(&sma->use_global_lock, 0); |
| } else { |
| sma->use_global_lock--; |
| } |
| } |
| |
| #define SEM_GLOBAL_LOCK (-1) |
| /* |
| * If the request contains only one semaphore operation, and there are |
| * no complex transactions pending, lock only the semaphore involved. |
| * Otherwise, lock the entire semaphore array, since we either have |
| * multiple semaphores in our own semops, or we need to look at |
| * semaphores from other pending complex operations. |
| */ |
| static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, |
| int nsops) |
| { |
| struct sem *sem; |
| int idx; |
| |
| if (nsops != 1) { |
| /* Complex operation - acquire a full lock */ |
| ipc_lock_object(&sma->sem_perm); |
| |
| /* Prevent parallel simple ops */ |
| complexmode_enter(sma); |
| return SEM_GLOBAL_LOCK; |
| } |
| |
| /* |
| * Only one semaphore affected - try to optimize locking. |
| * Optimized locking is possible if no complex operation |
| * is either enqueued or processed right now. |
| * |
| * Both facts are tracked by use_global_mode. |
| */ |
| idx = array_index_nospec(sops->sem_num, sma->sem_nsems); |
| sem = &sma->sems[idx]; |
| |
| /* |
| * Initial check for use_global_lock. Just an optimization, |
| * no locking, no memory barrier. |
| */ |
| if (!sma->use_global_lock) { |
| /* |
| * It appears that no complex operation is around. |
| * Acquire the per-semaphore lock. |
| */ |
| spin_lock(&sem->lock); |
| |
| /* pairs with smp_store_release() */ |
| if (!smp_load_acquire(&sma->use_global_lock)) { |
| /* fast path successful! */ |
| return sops->sem_num; |
| } |
| spin_unlock(&sem->lock); |
| } |
| |
| /* slow path: acquire the full lock */ |
| ipc_lock_object(&sma->sem_perm); |
| |
| if (sma->use_global_lock == 0) { |
| /* |
| * The use_global_lock mode ended while we waited for |
| * sma->sem_perm.lock. Thus we must switch to locking |
| * with sem->lock. |
| * Unlike in the fast path, there is no need to recheck |
| * sma->use_global_lock after we have acquired sem->lock: |
| * We own sma->sem_perm.lock, thus use_global_lock cannot |
| * change. |
| */ |
| spin_lock(&sem->lock); |
| |
| ipc_unlock_object(&sma->sem_perm); |
| return sops->sem_num; |
| } else { |
| /* |
| * Not a false alarm, thus continue to use the global lock |
| * mode. No need for complexmode_enter(), this was done by |
| * the caller that has set use_global_mode to non-zero. |
| */ |
| return SEM_GLOBAL_LOCK; |
| } |
| } |
| |
| static inline void sem_unlock(struct sem_array *sma, int locknum) |
| { |
| if (locknum == SEM_GLOBAL_LOCK) { |
| unmerge_queues(sma); |
| complexmode_tryleave(sma); |
| ipc_unlock_object(&sma->sem_perm); |
| } else { |
| struct sem *sem = &sma->sems[locknum]; |
| spin_unlock(&sem->lock); |
| } |
| } |
| |
| /* |
| * sem_lock_(check_) routines are called in the paths where the rwsem |
| * is not held. |
| * |
| * The caller holds the RCU read lock. |
| */ |
| static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) |
| { |
| struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id); |
| |
| if (IS_ERR(ipcp)) |
| return ERR_CAST(ipcp); |
| |
| return container_of(ipcp, struct sem_array, sem_perm); |
| } |
| |
| static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns, |
| int id) |
| { |
| struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id); |
| |
| if (IS_ERR(ipcp)) |
| return ERR_CAST(ipcp); |
| |
| return container_of(ipcp, struct sem_array, sem_perm); |
| } |
| |
| static inline void sem_lock_and_putref(struct sem_array *sma) |
| { |
| sem_lock(sma, NULL, -1); |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| } |
| |
| static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) |
| { |
| ipc_rmid(&sem_ids(ns), &s->sem_perm); |
| } |
| |
| static struct sem_array *sem_alloc(size_t nsems) |
| { |
| struct sem_array *sma; |
| size_t size; |
| |
| if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0])) |
| return NULL; |
| |
| size = sizeof(*sma) + nsems * sizeof(sma->sems[0]); |
| sma = kvmalloc(size, GFP_KERNEL); |
| if (unlikely(!sma)) |
| return NULL; |
| |
| memset(sma, 0, size); |
| |
| return sma; |
| } |
| |
| /** |
| * newary - Create a new semaphore set |
| * @ns: namespace |
| * @params: ptr to the structure that contains key, semflg and nsems |
| * |
| * Called with sem_ids.rwsem held (as a writer) |
| */ |
| static int newary(struct ipc_namespace *ns, struct ipc_params *params) |
| { |
| int retval; |
| struct sem_array *sma; |
| key_t key = params->key; |
| int nsems = params->u.nsems; |
| int semflg = params->flg; |
| int i; |
| |
| if (!nsems) |
| return -EINVAL; |
| if (ns->used_sems + nsems > ns->sc_semmns) |
| return -ENOSPC; |
| |
| sma = sem_alloc(nsems); |
| if (!sma) |
| return -ENOMEM; |
| |
| sma->sem_perm.mode = (semflg & S_IRWXUGO); |
| sma->sem_perm.key = key; |
| |
| sma->sem_perm.security = NULL; |
| retval = security_sem_alloc(&sma->sem_perm); |
| if (retval) { |
| kvfree(sma); |
| return retval; |
| } |
| |
| for (i = 0; i < nsems; i++) { |
| INIT_LIST_HEAD(&sma->sems[i].pending_alter); |
| INIT_LIST_HEAD(&sma->sems[i].pending_const); |
| spin_lock_init(&sma->sems[i].lock); |
| } |
| |
| sma->complex_count = 0; |
| sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; |
| INIT_LIST_HEAD(&sma->pending_alter); |
| INIT_LIST_HEAD(&sma->pending_const); |
| INIT_LIST_HEAD(&sma->list_id); |
| sma->sem_nsems = nsems; |
| sma->sem_ctime = ktime_get_real_seconds(); |
| |
| /* ipc_addid() locks sma upon success. */ |
| retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); |
| if (retval < 0) { |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| return retval; |
| } |
| ns->used_sems += nsems; |
| |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| |
| return sma->sem_perm.id; |
| } |
| |
| |
| /* |
| * Called with sem_ids.rwsem and ipcp locked. |
| */ |
| static inline int sem_more_checks(struct kern_ipc_perm *ipcp, |
| struct ipc_params *params) |
| { |
| struct sem_array *sma; |
| |
| sma = container_of(ipcp, struct sem_array, sem_perm); |
| if (params->u.nsems > sma->sem_nsems) |
| return -EINVAL; |
| |
| return 0; |
| } |
| |
| long ksys_semget(key_t key, int nsems, int semflg) |
| { |
| struct ipc_namespace *ns; |
| static const struct ipc_ops sem_ops = { |
| .getnew = newary, |
| .associate = security_sem_associate, |
| .more_checks = sem_more_checks, |
| }; |
| struct ipc_params sem_params; |
| |
| ns = current->nsproxy->ipc_ns; |
| |
| if (nsems < 0 || nsems > ns->sc_semmsl) |
| return -EINVAL; |
| |
| sem_params.key = key; |
| sem_params.flg = semflg; |
| sem_params.u.nsems = nsems; |
| |
| return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); |
| } |
| |
| SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) |
| { |
| return ksys_semget(key, nsems, semflg); |
| } |
| |
| /** |
| * perform_atomic_semop[_slow] - Attempt to perform semaphore |
| * operations on a given array. |
| * @sma: semaphore array |
| * @q: struct sem_queue that describes the operation |
| * |
| * Caller blocking are as follows, based the value |
| * indicated by the semaphore operation (sem_op): |
| * |
| * (1) >0 never blocks. |
| * (2) 0 (wait-for-zero operation): semval is non-zero. |
| * (3) <0 attempting to decrement semval to a value smaller than zero. |
| * |
| * Returns 0 if the operation was possible. |
| * Returns 1 if the operation is impossible, the caller must sleep. |
| * Returns <0 for error codes. |
| */ |
| static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q) |
| { |
| int result, sem_op, nsops; |
| struct pid *pid; |
| struct sembuf *sop; |
| struct sem *curr; |
| struct sembuf *sops; |
| struct sem_undo *un; |
| |
| sops = q->sops; |
| nsops = q->nsops; |
| un = q->undo; |
| |
| for (sop = sops; sop < sops + nsops; sop++) { |
| int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); |
| curr = &sma->sems[idx]; |
| sem_op = sop->sem_op; |
| result = curr->semval; |
| |
| if (!sem_op && result) |
| goto would_block; |
| |
| result += sem_op; |
| if (result < 0) |
| goto would_block; |
| if (result > SEMVMX) |
| goto out_of_range; |
| |
| if (sop->sem_flg & SEM_UNDO) { |
| int undo = un->semadj[sop->sem_num] - sem_op; |
| /* Exceeding the undo range is an error. */ |
| if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
| goto out_of_range; |
| un->semadj[sop->sem_num] = undo; |
| } |
| |
| curr->semval = result; |
| } |
| |
| sop--; |
| pid = q->pid; |
| while (sop >= sops) { |
| ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid); |
| sop--; |
| } |
| |
| return 0; |
| |
| out_of_range: |
| result = -ERANGE; |
| goto undo; |
| |
| would_block: |
| q->blocking = sop; |
| |
| if (sop->sem_flg & IPC_NOWAIT) |
| result = -EAGAIN; |
| else |
| result = 1; |
| |
| undo: |
| sop--; |
| while (sop >= sops) { |
| sem_op = sop->sem_op; |
| sma->sems[sop->sem_num].semval -= sem_op; |
| if (sop->sem_flg & SEM_UNDO) |
| un->semadj[sop->sem_num] += sem_op; |
| sop--; |
| } |
| |
| return result; |
| } |
| |
| static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q) |
| { |
| int result, sem_op, nsops; |
| struct sembuf *sop; |
| struct sem *curr; |
| struct sembuf *sops; |
| struct sem_undo *un; |
| |
| sops = q->sops; |
| nsops = q->nsops; |
| un = q->undo; |
| |
| if (unlikely(q->dupsop)) |
| return perform_atomic_semop_slow(sma, q); |
| |
| /* |
| * We scan the semaphore set twice, first to ensure that the entire |
| * operation can succeed, therefore avoiding any pointless writes |
| * to shared memory and having to undo such changes in order to block |
| * until the operations can go through. |
| */ |
| for (sop = sops; sop < sops + nsops; sop++) { |
| int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); |
| |
| curr = &sma->sems[idx]; |
| sem_op = sop->sem_op; |
| result = curr->semval; |
| |
| if (!sem_op && result) |
| goto would_block; /* wait-for-zero */ |
| |
| result += sem_op; |
| if (result < 0) |
| goto would_block; |
| |
| if (result > SEMVMX) |
| return -ERANGE; |
| |
| if (sop->sem_flg & SEM_UNDO) { |
| int undo = un->semadj[sop->sem_num] - sem_op; |
| |
| /* Exceeding the undo range is an error. */ |
| if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
| return -ERANGE; |
| } |
| } |
| |
| for (sop = sops; sop < sops + nsops; sop++) { |
| curr = &sma->sems[sop->sem_num]; |
| sem_op = sop->sem_op; |
| result = curr->semval; |
| |
| if (sop->sem_flg & SEM_UNDO) { |
| int undo = un->semadj[sop->sem_num] - sem_op; |
| |
| un->semadj[sop->sem_num] = undo; |
| } |
| curr->semval += sem_op; |
| ipc_update_pid(&curr->sempid, q->pid); |
| } |
| |
| return 0; |
| |
| would_block: |
| q->blocking = sop; |
| return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1; |
| } |
| |
| static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error, |
| struct wake_q_head *wake_q) |
| { |
| wake_q_add(wake_q, q->sleeper); |
| /* |
| * Rely on the above implicit barrier, such that we can |
| * ensure that we hold reference to the task before setting |
| * q->status. Otherwise we could race with do_exit if the |
| * task is awoken by an external event before calling |
| * wake_up_process(). |
| */ |
| WRITE_ONCE(q->status, error); |
| } |
| |
| static void unlink_queue(struct sem_array *sma, struct sem_queue *q) |
| { |
| list_del(&q->list); |
| if (q->nsops > 1) |
| sma->complex_count--; |
| } |
| |
| /** check_restart(sma, q) |
| * @sma: semaphore array |
| * @q: the operation that just completed |
| * |
| * update_queue is O(N^2) when it restarts scanning the whole queue of |
| * waiting operations. Therefore this function checks if the restart is |
| * really necessary. It is called after a previously waiting operation |
| * modified the array. |
| * Note that wait-for-zero operations are handled without restart. |
| */ |
| static inline int check_restart(struct sem_array *sma, struct sem_queue *q) |
| { |
| /* pending complex alter operations are too difficult to analyse */ |
| if (!list_empty(&sma->pending_alter)) |
| return 1; |
| |
| /* we were a sleeping complex operation. Too difficult */ |
| if (q->nsops > 1) |
| return 1; |
| |
| /* It is impossible that someone waits for the new value: |
| * - complex operations always restart. |
| * - wait-for-zero are handled seperately. |
| * - q is a previously sleeping simple operation that |
| * altered the array. It must be a decrement, because |
| * simple increments never sleep. |
| * - If there are older (higher priority) decrements |
| * in the queue, then they have observed the original |
| * semval value and couldn't proceed. The operation |
| * decremented to value - thus they won't proceed either. |
| */ |
| return 0; |
| } |
| |
| /** |
| * wake_const_ops - wake up non-alter tasks |
| * @sma: semaphore array. |
| * @semnum: semaphore that was modified. |
| * @wake_q: lockless wake-queue head. |
| * |
| * wake_const_ops must be called after a semaphore in a semaphore array |
| * was set to 0. If complex const operations are pending, wake_const_ops must |
| * be called with semnum = -1, as well as with the number of each modified |
| * semaphore. |
| * The tasks that must be woken up are added to @wake_q. The return code |
| * is stored in q->pid. |
| * The function returns 1 if at least one operation was completed successfully. |
| */ |
| static int wake_const_ops(struct sem_array *sma, int semnum, |
| struct wake_q_head *wake_q) |
| { |
| struct sem_queue *q, *tmp; |
| struct list_head *pending_list; |
| int semop_completed = 0; |
| |
| if (semnum == -1) |
| pending_list = &sma->pending_const; |
| else |
| pending_list = &sma->sems[semnum].pending_const; |
| |
| list_for_each_entry_safe(q, tmp, pending_list, list) { |
| int error = perform_atomic_semop(sma, q); |
| |
| if (error > 0) |
| continue; |
| /* operation completed, remove from queue & wakeup */ |
| unlink_queue(sma, q); |
| |
| wake_up_sem_queue_prepare(q, error, wake_q); |
| if (error == 0) |
| semop_completed = 1; |
| } |
| |
| return semop_completed; |
| } |
| |
| /** |
| * do_smart_wakeup_zero - wakeup all wait for zero tasks |
| * @sma: semaphore array |
| * @sops: operations that were performed |
| * @nsops: number of operations |
| * @wake_q: lockless wake-queue head |
| * |
| * Checks all required queue for wait-for-zero operations, based |
| * on the actual changes that were performed on the semaphore array. |
| * The function returns 1 if at least one operation was completed successfully. |
| */ |
| static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops, |
| int nsops, struct wake_q_head *wake_q) |
| { |
| int i; |
| int semop_completed = 0; |
| int got_zero = 0; |
| |
| /* first: the per-semaphore queues, if known */ |
| if (sops) { |
| for (i = 0; i < nsops; i++) { |
| int num = sops[i].sem_num; |
| |
| if (sma->sems[num].semval == 0) { |
| got_zero = 1; |
| semop_completed |= wake_const_ops(sma, num, wake_q); |
| } |
| } |
| } else { |
| /* |
| * No sops means modified semaphores not known. |
| * Assume all were changed. |
| */ |
| for (i = 0; i < sma->sem_nsems; i++) { |
| if (sma->sems[i].semval == 0) { |
| got_zero = 1; |
| semop_completed |= wake_const_ops(sma, i, wake_q); |
| } |
| } |
| } |
| /* |
| * If one of the modified semaphores got 0, |
| * then check the global queue, too. |
| */ |
| if (got_zero) |
| semop_completed |= wake_const_ops(sma, -1, wake_q); |
| |
| return semop_completed; |
| } |
| |
| |
| /** |
| * update_queue - look for tasks that can be completed. |
| * @sma: semaphore array. |
| * @semnum: semaphore that was modified. |
| * @wake_q: lockless wake-queue head. |
| * |
| * update_queue must be called after a semaphore in a semaphore array |
| * was modified. If multiple semaphores were modified, update_queue must |
| * be called with semnum = -1, as well as with the number of each modified |
| * semaphore. |
| * The tasks that must be woken up are added to @wake_q. The return code |
| * is stored in q->pid. |
| * The function internally checks if const operations can now succeed. |
| * |
| * The function return 1 if at least one semop was completed successfully. |
| */ |
| static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q) |
| { |
| struct sem_queue *q, *tmp; |
| struct list_head *pending_list; |
| int semop_completed = 0; |
| |
| if (semnum == -1) |
| pending_list = &sma->pending_alter; |
| else |
| pending_list = &sma->sems[semnum].pending_alter; |
| |
| again: |
| list_for_each_entry_safe(q, tmp, pending_list, list) { |
| int error, restart; |
| |
| /* If we are scanning the single sop, per-semaphore list of |
| * one semaphore and that semaphore is 0, then it is not |
| * necessary to scan further: simple increments |
| * that affect only one entry succeed immediately and cannot |
| * be in the per semaphore pending queue, and decrements |
| * cannot be successful if the value is already 0. |
| */ |
| if (semnum != -1 && sma->sems[semnum].semval == 0) |
| break; |
| |
| error = perform_atomic_semop(sma, q); |
| |
| /* Does q->sleeper still need to sleep? */ |
| if (error > 0) |
| continue; |
| |
| unlink_queue(sma, q); |
| |
| if (error) { |
| restart = 0; |
| } else { |
| semop_completed = 1; |
| do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q); |
| restart = check_restart(sma, q); |
| } |
| |
| wake_up_sem_queue_prepare(q, error, wake_q); |
| if (restart) |
| goto again; |
| } |
| return semop_completed; |
| } |
| |
| /** |
| * set_semotime - set sem_otime |
| * @sma: semaphore array |
| * @sops: operations that modified the array, may be NULL |
| * |
| * sem_otime is replicated to avoid cache line trashing. |
| * This function sets one instance to the current time. |
| */ |
| static void set_semotime(struct sem_array *sma, struct sembuf *sops) |
| { |
| if (sops == NULL) { |
| sma->sems[0].sem_otime = ktime_get_real_seconds(); |
| } else { |
| sma->sems[sops[0].sem_num].sem_otime = |
| ktime_get_real_seconds(); |
| } |
| } |
| |
| /** |
| * do_smart_update - optimized update_queue |
| * @sma: semaphore array |
| * @sops: operations that were performed |
| * @nsops: number of operations |
| * @otime: force setting otime |
| * @wake_q: lockless wake-queue head |
| * |
| * do_smart_update() does the required calls to update_queue and wakeup_zero, |
| * based on the actual changes that were performed on the semaphore array. |
| * Note that the function does not do the actual wake-up: the caller is |
| * responsible for calling wake_up_q(). |
| * It is safe to perform this call after dropping all locks. |
| */ |
| static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, |
| int otime, struct wake_q_head *wake_q) |
| { |
| int i; |
| |
| otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q); |
| |
| if (!list_empty(&sma->pending_alter)) { |
| /* semaphore array uses the global queue - just process it. */ |
| otime |= update_queue(sma, -1, wake_q); |
| } else { |
| if (!sops) { |
| /* |
| * No sops, thus the modified semaphores are not |
| * known. Check all. |
| */ |
| for (i = 0; i < sma->sem_nsems; i++) |
| otime |= update_queue(sma, i, wake_q); |
| } else { |
| /* |
| * Check the semaphores that were increased: |
| * - No complex ops, thus all sleeping ops are |
| * decrease. |
| * - if we decreased the value, then any sleeping |
| * semaphore ops wont be able to run: If the |
| * previous value was too small, then the new |
| * value will be too small, too. |
| */ |
| for (i = 0; i < nsops; i++) { |
| if (sops[i].sem_op > 0) { |
| otime |= update_queue(sma, |
| sops[i].sem_num, wake_q); |
| } |
| } |
| } |
| } |
| if (otime) |
| set_semotime(sma, sops); |
| } |
| |
| /* |
| * check_qop: Test if a queued operation sleeps on the semaphore semnum |
| */ |
| static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, |
| bool count_zero) |
| { |
| struct sembuf *sop = q->blocking; |
| |
| /* |
| * Linux always (since 0.99.10) reported a task as sleeping on all |
| * semaphores. This violates SUS, therefore it was changed to the |
| * standard compliant behavior. |
| * Give the administrators a chance to notice that an application |
| * might misbehave because it relies on the Linux behavior. |
| */ |
| pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n" |
| "The task %s (%d) triggered the difference, watch for misbehavior.\n", |
| current->comm, task_pid_nr(current)); |
| |
| if (sop->sem_num != semnum) |
| return 0; |
| |
| if (count_zero && sop->sem_op == 0) |
| return 1; |
| if (!count_zero && sop->sem_op < 0) |
| return 1; |
| |
| return 0; |
| } |
| |
| /* The following counts are associated to each semaphore: |
| * semncnt number of tasks waiting on semval being nonzero |
| * semzcnt number of tasks waiting on semval being zero |
| * |
| * Per definition, a task waits only on the semaphore of the first semop |
| * that cannot proceed, even if additional operation would block, too. |
| */ |
| static int count_semcnt(struct sem_array *sma, ushort semnum, |
| bool count_zero) |
| { |
| struct list_head *l; |
| struct sem_queue *q; |
| int semcnt; |
| |
| semcnt = 0; |
| /* First: check the simple operations. They are easy to evaluate */ |
| if (count_zero) |
| l = &sma->sems[semnum].pending_const; |
| else |
| l = &sma->sems[semnum].pending_alter; |
| |
| list_for_each_entry(q, l, list) { |
| /* all task on a per-semaphore list sleep on exactly |
| * that semaphore |
| */ |
| semcnt++; |
| } |
| |
| /* Then: check the complex operations. */ |
| list_for_each_entry(q, &sma->pending_alter, list) { |
| semcnt += check_qop(sma, semnum, q, count_zero); |
| } |
| if (count_zero) { |
| list_for_each_entry(q, &sma->pending_const, list) { |
| semcnt += check_qop(sma, semnum, q, count_zero); |
| } |
| } |
| return semcnt; |
| } |
| |
| /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked |
| * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem |
| * remains locked on exit. |
| */ |
| static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) |
| { |
| struct sem_undo *un, *tu; |
| struct sem_queue *q, *tq; |
| struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
| int i; |
| DEFINE_WAKE_Q(wake_q); |
| |
| /* Free the existing undo structures for this semaphore set. */ |
| ipc_assert_locked_object(&sma->sem_perm); |
| list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { |
| list_del(&un->list_id); |
| spin_lock(&un->ulp->lock); |
| un->semid = -1; |
| list_del_rcu(&un->list_proc); |
| spin_unlock(&un->ulp->lock); |
| kfree_rcu(un, rcu); |
| } |
| |
| /* Wake up all pending processes and let them fail with EIDRM. */ |
| list_for_each_entry_safe(q, tq, &sma->pending_const, list) { |
| unlink_queue(sma, q); |
| wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| } |
| |
| list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
| unlink_queue(sma, q); |
| wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| } |
| for (i = 0; i < sma->sem_nsems; i++) { |
| struct sem *sem = &sma->sems[i]; |
| list_for_each_entry_safe(q, tq, &sem->pending_const, list) { |
| unlink_queue(sma, q); |
| wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| } |
| list_for_each_entry_safe(q, tq, &sem->pending_alter, list) { |
| unlink_queue(sma, q); |
| wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| } |
| ipc_update_pid(&sem->sempid, NULL); |
| } |
| |
| /* Remove the semaphore set from the IDR */ |
| sem_rmid(ns, sma); |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| |
| wake_up_q(&wake_q); |
| ns->used_sems -= sma->sem_nsems; |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| } |
| |
| static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) |
| { |
| switch (version) { |
| case IPC_64: |
| return copy_to_user(buf, in, sizeof(*in)); |
| case IPC_OLD: |
| { |
| struct semid_ds out; |
| |
| memset(&out, 0, sizeof(out)); |
| |
| ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); |
| |
| out.sem_otime = in->sem_otime; |
| out.sem_ctime = in->sem_ctime; |
| out.sem_nsems = in->sem_nsems; |
| |
| return copy_to_user(buf, &out, sizeof(out)); |
| } |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| static time64_t get_semotime(struct sem_array *sma) |
| { |
| int i; |
| time64_t res; |
| |
| res = sma->sems[0].sem_otime; |
| for (i = 1; i < sma->sem_nsems; i++) { |
| time64_t to = sma->sems[i].sem_otime; |
| |
| if (to > res) |
| res = to; |
| } |
| return res; |
| } |
| |
| static int semctl_stat(struct ipc_namespace *ns, int semid, |
| int cmd, struct semid64_ds *semid64) |
| { |
| struct sem_array *sma; |
| time64_t semotime; |
| int err; |
| |
| memset(semid64, 0, sizeof(*semid64)); |
| |
| rcu_read_lock(); |
| if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) { |
| sma = sem_obtain_object(ns, semid); |
| if (IS_ERR(sma)) { |
| err = PTR_ERR(sma); |
| goto out_unlock; |
| } |
| } else { /* IPC_STAT */ |
| sma = sem_obtain_object_check(ns, semid); |
| if (IS_ERR(sma)) { |
| err = PTR_ERR(sma); |
| goto out_unlock; |
| } |
| } |
| |
| /* see comment for SHM_STAT_ANY */ |
| if (cmd == SEM_STAT_ANY) |
| audit_ipc_obj(&sma->sem_perm); |
| else { |
| err = -EACCES; |
| if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) |
| goto out_unlock; |
| } |
| |
| err = security_sem_semctl(&sma->sem_perm, cmd); |
| if (err) |
| goto out_unlock; |
| |
| ipc_lock_object(&sma->sem_perm); |
| |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| ipc_unlock_object(&sma->sem_perm); |
| err = -EIDRM; |
| goto out_unlock; |
| } |
| |
| kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm); |
| semotime = get_semotime(sma); |
| semid64->sem_otime = semotime; |
| semid64->sem_ctime = sma->sem_ctime; |
| #ifndef CONFIG_64BIT |
| semid64->sem_otime_high = semotime >> 32; |
| semid64->sem_ctime_high = sma->sem_ctime >> 32; |
| #endif |
| semid64->sem_nsems = sma->sem_nsems; |
| |
| if (cmd == IPC_STAT) { |
| /* |
| * As defined in SUS: |
| * Return 0 on success |
| */ |
| err = 0; |
| } else { |
| /* |
| * SEM_STAT and SEM_STAT_ANY (both Linux specific) |
| * Return the full id, including the sequence number |
| */ |
| err = sma->sem_perm.id; |
| } |
| ipc_unlock_object(&sma->sem_perm); |
| out_unlock: |
| rcu_read_unlock(); |
| return err; |
| } |
| |
| static int semctl_info(struct ipc_namespace *ns, int semid, |
| int cmd, void __user *p) |
| { |
| struct seminfo seminfo; |
| int max_idx; |
| int err; |
| |
| err = security_sem_semctl(NULL, cmd); |
| if (err) |
| return err; |
| |
| memset(&seminfo, 0, sizeof(seminfo)); |
| seminfo.semmni = ns->sc_semmni; |
| seminfo.semmns = ns->sc_semmns; |
| seminfo.semmsl = ns->sc_semmsl; |
| seminfo.semopm = ns->sc_semopm; |
| seminfo.semvmx = SEMVMX; |
| seminfo.semmnu = SEMMNU; |
| seminfo.semmap = SEMMAP; |
| seminfo.semume = SEMUME; |
| down_read(&sem_ids(ns).rwsem); |
| if (cmd == SEM_INFO) { |
| seminfo.semusz = sem_ids(ns).in_use; |
| seminfo.semaem = ns->used_sems; |
| } else { |
| seminfo.semusz = SEMUSZ; |
| seminfo.semaem = SEMAEM; |
| } |
| max_idx = ipc_get_maxidx(&sem_ids(ns)); |
| up_read(&sem_ids(ns).rwsem); |
| if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) |
| return -EFAULT; |
| return (max_idx < 0) ? 0 : max_idx; |
| } |
| |
| static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, |
| int val) |
| { |
| struct sem_undo *un; |
| struct sem_array *sma; |
| struct sem *curr; |
| int err; |
| DEFINE_WAKE_Q(wake_q); |
| |
| if (val > SEMVMX || val < 0) |
| return -ERANGE; |
| |
| rcu_read_lock(); |
| sma = sem_obtain_object_check(ns, semid); |
| if (IS_ERR(sma)) { |
| rcu_read_unlock(); |
| return PTR_ERR(sma); |
| } |
| |
| if (semnum < 0 || semnum >= sma->sem_nsems) { |
| rcu_read_unlock(); |
| return -EINVAL; |
| } |
| |
| |
| if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) { |
| rcu_read_unlock(); |
| return -EACCES; |
| } |
| |
| err = security_sem_semctl(&sma->sem_perm, SETVAL); |
| if (err) { |
| rcu_read_unlock(); |
| return -EACCES; |
| } |
| |
| sem_lock(sma, NULL, -1); |
| |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| return -EIDRM; |
| } |
| |
| semnum = array_index_nospec(semnum, sma->sem_nsems); |
| curr = &sma->sems[semnum]; |
| |
| ipc_assert_locked_object(&sma->sem_perm); |
| list_for_each_entry(un, &sma->list_id, list_id) |
| un->semadj[semnum] = 0; |
| |
| curr->semval = val; |
| ipc_update_pid(&curr->sempid, task_tgid(current)); |
| sma->sem_ctime = ktime_get_real_seconds(); |
| /* maybe some queued-up processes were waiting for this */ |
| do_smart_update(sma, NULL, 0, 0, &wake_q); |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| wake_up_q(&wake_q); |
| return 0; |
| } |
| |
| static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, |
| int cmd, void __user *p) |
| { |
| struct sem_array *sma; |
| struct sem *curr; |
| int err, nsems; |
| ushort fast_sem_io[SEMMSL_FAST]; |
| ushort *sem_io = fast_sem_io; |
| DEFINE_WAKE_Q(wake_q); |
| |
| rcu_read_lock(); |
| sma = sem_obtain_object_check(ns, semid); |
| if (IS_ERR(sma)) { |
| rcu_read_unlock(); |
| return PTR_ERR(sma); |
| } |
| |
| nsems = sma->sem_nsems; |
| |
| err = -EACCES; |
| if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO)) |
| goto out_rcu_wakeup; |
| |
| err = security_sem_semctl(&sma->sem_perm, cmd); |
| if (err) |
| goto out_rcu_wakeup; |
| |
| err = -EACCES; |
| switch (cmd) { |
| case GETALL: |
| { |
| ushort __user *array = p; |
| int i; |
| |
| sem_lock(sma, NULL, -1); |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| err = -EIDRM; |
| goto out_unlock; |
| } |
| if (nsems > SEMMSL_FAST) { |
| if (!ipc_rcu_getref(&sma->sem_perm)) { |
| err = -EIDRM; |
| goto out_unlock; |
| } |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| sem_io = kvmalloc_array(nsems, sizeof(ushort), |
| GFP_KERNEL); |
| if (sem_io == NULL) { |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| return -ENOMEM; |
| } |
| |
| rcu_read_lock(); |
| sem_lock_and_putref(sma); |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| err = -EIDRM; |
| goto out_unlock; |
| } |
| } |
| for (i = 0; i < sma->sem_nsems; i++) |
| sem_io[i] = sma->sems[i].semval; |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| err = 0; |
| if (copy_to_user(array, sem_io, nsems*sizeof(ushort))) |
| err = -EFAULT; |
| goto out_free; |
| } |
| case SETALL: |
| { |
| int i; |
| struct sem_undo *un; |
| |
| if (!ipc_rcu_getref(&sma->sem_perm)) { |
| err = -EIDRM; |
| goto out_rcu_wakeup; |
| } |
| rcu_read_unlock(); |
| |
| if (nsems > SEMMSL_FAST) { |
| sem_io = kvmalloc_array(nsems, sizeof(ushort), |
| GFP_KERNEL); |
| if (sem_io == NULL) { |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| return -ENOMEM; |
| } |
| } |
| |
| if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) { |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| err = -EFAULT; |
| goto out_free; |
| } |
| |
| for (i = 0; i < nsems; i++) { |
| if (sem_io[i] > SEMVMX) { |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| err = -ERANGE; |
| goto out_free; |
| } |
| } |
| rcu_read_lock(); |
| sem_lock_and_putref(sma); |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| err = -EIDRM; |
| goto out_unlock; |
| } |
| |
| for (i = 0; i < nsems; i++) { |
| sma->sems[i].semval = sem_io[i]; |
| ipc_update_pid(&sma->sems[i].sempid, task_tgid(current)); |
| } |
| |
| ipc_assert_locked_object(&sma->sem_perm); |
| list_for_each_entry(un, &sma->list_id, list_id) { |
| for (i = 0; i < nsems; i++) |
| un->semadj[i] = 0; |
| } |
| sma->sem_ctime = ktime_get_real_seconds(); |
| /* maybe some queued-up processes were waiting for this */ |
| do_smart_update(sma, NULL, 0, 0, &wake_q); |
| err = 0; |
| goto out_unlock; |
| } |
| /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */ |
| } |
| err = -EINVAL; |
| if (semnum < 0 || semnum >= nsems) |
| goto out_rcu_wakeup; |
| |
| sem_lock(sma, NULL, -1); |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| err = -EIDRM; |
| goto out_unlock; |
| } |
| |
| semnum = array_index_nospec(semnum, nsems); |
| curr = &sma->sems[semnum]; |
| |
| switch (cmd) { |
| case GETVAL: |
| err = curr->semval; |
| goto out_unlock; |
| case GETPID: |
| err = pid_vnr(curr->sempid); |
| goto out_unlock; |
| case GETNCNT: |
| err = count_semcnt(sma, semnum, 0); |
| goto out_unlock; |
| case GETZCNT: |
| err = count_semcnt(sma, semnum, 1); |
| goto out_unlock; |
| } |
| |
| out_unlock: |
| sem_unlock(sma, -1); |
| out_rcu_wakeup: |
| rcu_read_unlock(); |
| wake_up_q(&wake_q); |
| out_free: |
| if (sem_io != fast_sem_io) |
| kvfree(sem_io); |
| return err; |
| } |
| |
| static inline unsigned long |
| copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) |
| { |
| switch (version) { |
| case IPC_64: |
| if (copy_from_user(out, buf, sizeof(*out))) |
| return -EFAULT; |
| return 0; |
| case IPC_OLD: |
| { |
| struct semid_ds tbuf_old; |
| |
| if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) |
| return -EFAULT; |
| |
| out->sem_perm.uid = tbuf_old.sem_perm.uid; |
| out->sem_perm.gid = tbuf_old.sem_perm.gid; |
| out->sem_perm.mode = tbuf_old.sem_perm.mode; |
| |
| return 0; |
| } |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| /* |
| * This function handles some semctl commands which require the rwsem |
| * to be held in write mode. |
| * NOTE: no locks must be held, the rwsem is taken inside this function. |
| */ |
| static int semctl_down(struct ipc_namespace *ns, int semid, |
| int cmd, struct semid64_ds *semid64) |
| { |
| struct sem_array *sma; |
| int err; |
| struct kern_ipc_perm *ipcp; |
| |
| down_write(&sem_ids(ns).rwsem); |
| rcu_read_lock(); |
| |
| ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd, |
| &semid64->sem_perm, 0); |
| if (IS_ERR(ipcp)) { |
| err = PTR_ERR(ipcp); |
| goto out_unlock1; |
| } |
| |
| sma = container_of(ipcp, struct sem_array, sem_perm); |
| |
| err = security_sem_semctl(&sma->sem_perm, cmd); |
| if (err) |
| goto out_unlock1; |
| |
| switch (cmd) { |
| case IPC_RMID: |
| sem_lock(sma, NULL, -1); |
| /* freeary unlocks the ipc object and rcu */ |
| freeary(ns, ipcp); |
| goto out_up; |
| case IPC_SET: |
| sem_lock(sma, NULL, -1); |
| err = ipc_update_perm(&semid64->sem_perm, ipcp); |
| if (err) |
| goto out_unlock0; |
| sma->sem_ctime = ktime_get_real_seconds(); |
| break; |
| default: |
| err = -EINVAL; |
| goto out_unlock1; |
| } |
| |
| out_unlock0: |
| sem_unlock(sma, -1); |
| out_unlock1: |
| rcu_read_unlock(); |
| out_up: |
| up_write(&sem_ids(ns).rwsem); |
| return err; |
| } |
| |
| static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version) |
| { |
| struct ipc_namespace *ns; |
| void __user *p = (void __user *)arg; |
| struct semid64_ds semid64; |
| int err; |
| |
| if (semid < 0) |
| return -EINVAL; |
| |
| ns = current->nsproxy->ipc_ns; |
| |
| switch (cmd) { |
| case IPC_INFO: |
| case SEM_INFO: |
| return semctl_info(ns, semid, cmd, p); |
| case IPC_STAT: |
| case SEM_STAT: |
| case SEM_STAT_ANY: |
| err = semctl_stat(ns, semid, cmd, &semid64); |
| if (err < 0) |
| return err; |
| if (copy_semid_to_user(p, &semid64, version)) |
| err = -EFAULT; |
| return err; |
| case GETALL: |
| case GETVAL: |
| case GETPID: |
| case GETNCNT: |
| case GETZCNT: |
| case SETALL: |
| return semctl_main(ns, semid, semnum, cmd, p); |
| case SETVAL: { |
| int val; |
| #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN) |
| /* big-endian 64bit */ |
| val = arg >> 32; |
| #else |
| /* 32bit or little-endian 64bit */ |
| val = arg; |
| #endif |
| return semctl_setval(ns, semid, semnum, val); |
| } |
| case IPC_SET: |
| if (copy_semid_from_user(&semid64, p, version)) |
| return -EFAULT; |
| case IPC_RMID: |
| return semctl_down(ns, semid, cmd, &semid64); |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) |
| { |
| return ksys_semctl(semid, semnum, cmd, arg, IPC_64); |
| } |
| |
| #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION |
| long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg) |
| { |
| int version = ipc_parse_version(&cmd); |
| |
| return ksys_semctl(semid, semnum, cmd, arg, version); |
| } |
| |
| SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) |
| { |
| return ksys_old_semctl(semid, semnum, cmd, arg); |
| } |
| #endif |
| |
| #ifdef CONFIG_COMPAT |
| |
| struct compat_semid_ds { |
| struct compat_ipc_perm sem_perm; |
| old_time32_t sem_otime; |
| old_time32_t sem_ctime; |
| compat_uptr_t sem_base; |
| compat_uptr_t sem_pending; |
| compat_uptr_t sem_pending_last; |
| compat_uptr_t undo; |
| unsigned short sem_nsems; |
| }; |
| |
| static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf, |
| int version) |
| { |
| memset(out, 0, sizeof(*out)); |
| if (version == IPC_64) { |
| struct compat_semid64_ds __user *p = buf; |
| return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm); |
| } else { |
| struct compat_semid_ds __user *p = buf; |
| return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm); |
| } |
| } |
| |
| static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in, |
| int version) |
| { |
| if (version == IPC_64) { |
| struct compat_semid64_ds v; |
| memset(&v, 0, sizeof(v)); |
| to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm); |
| v.sem_otime = lower_32_bits(in->sem_otime); |
| v.sem_otime_high = upper_32_bits(in->sem_otime); |
| v.sem_ctime = lower_32_bits(in->sem_ctime); |
| v.sem_ctime_high = upper_32_bits(in->sem_ctime); |
| v.sem_nsems = in->sem_nsems; |
| return copy_to_user(buf, &v, sizeof(v)); |
| } else { |
| struct compat_semid_ds v; |
| memset(&v, 0, sizeof(v)); |
| to_compat_ipc_perm(&v.sem_perm, &in->sem_perm); |
| v.sem_otime = in->sem_otime; |
| v.sem_ctime = in->sem_ctime; |
| v.sem_nsems = in->sem_nsems; |
| return copy_to_user(buf, &v, sizeof(v)); |
| } |
| } |
| |
| static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version) |
| { |
| void __user *p = compat_ptr(arg); |
| struct ipc_namespace *ns; |
| struct semid64_ds semid64; |
| int err; |
| |
| ns = current->nsproxy->ipc_ns; |
| |
| if (semid < 0) |
| return -EINVAL; |
| |
| switch (cmd & (~IPC_64)) { |
| case IPC_INFO: |
| case SEM_INFO: |
| return semctl_info(ns, semid, cmd, p); |
| case IPC_STAT: |
| case SEM_STAT: |
| case SEM_STAT_ANY: |
| err = semctl_stat(ns, semid, cmd, &semid64); |
| if (err < 0) |
| return err; |
| if (copy_compat_semid_to_user(p, &semid64, version)) |
| err = -EFAULT; |
| return err; |
| case GETVAL: |
| case GETPID: |
| case GETNCNT: |
| case GETZCNT: |
| case GETALL: |
| case SETALL: |
| return semctl_main(ns, semid, semnum, cmd, p); |
| case SETVAL: |
| return semctl_setval(ns, semid, semnum, arg); |
| case IPC_SET: |
| if (copy_compat_semid_from_user(&semid64, p, version)) |
| return -EFAULT; |
| /* fallthru */ |
| case IPC_RMID: |
| return semctl_down(ns, semid, cmd, &semid64); |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg) |
| { |
| return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64); |
| } |
| |
| #ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION |
| long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg) |
| { |
| int version = compat_ipc_parse_version(&cmd); |
| |
| return compat_ksys_semctl(semid, semnum, cmd, arg, version); |
| } |
| |
| COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg) |
| { |
| return compat_ksys_old_semctl(semid, semnum, cmd, arg); |
| } |
| #endif |
| #endif |
| |
| /* If the task doesn't already have a undo_list, then allocate one |
| * here. We guarantee there is only one thread using this undo list, |
| * and current is THE ONE |
| * |
| * If this allocation and assignment succeeds, but later |
| * portions of this code fail, there is no need to free the sem_undo_list. |
| * Just let it stay associated with the task, and it'll be freed later |
| * at exit time. |
| * |
| * This can block, so callers must hold no locks. |
| */ |
| static inline int get_undo_list(struct sem_undo_list **undo_listp) |
| { |
| struct sem_undo_list *undo_list; |
| |
| undo_list = current->sysvsem.undo_list; |
| if (!undo_list) { |
| undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL); |
| if (undo_list == NULL) |
| return -ENOMEM; |
| spin_lock_init(&undo_list->lock); |
| refcount_set(&undo_list->refcnt, 1); |
| INIT_LIST_HEAD(&undo_list->list_proc); |
| |
| current->sysvsem.undo_list = undo_list; |
| } |
| *undo_listp = undo_list; |
| return 0; |
| } |
| |
| static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) |
| { |
| struct sem_undo *un; |
| |
| list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) { |
| if (un->semid == semid) |
| return un; |
| } |
| return NULL; |
| } |
| |
| static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) |
| { |
| struct sem_undo *un; |
| |
| assert_spin_locked(&ulp->lock); |
| |
| un = __lookup_undo(ulp, semid); |
| if (un) { |
| list_del_rcu(&un->list_proc); |
| list_add_rcu(&un->list_proc, &ulp->list_proc); |
| } |
| return un; |
| } |
| |
| /** |
| * find_alloc_undo - lookup (and if not present create) undo array |
| * @ns: namespace |
| * @semid: semaphore array id |
| * |
| * The function looks up (and if not present creates) the undo structure. |
| * The size of the undo structure depends on the size of the semaphore |
| * array, thus the alloc path is not that straightforward. |
| * Lifetime-rules: sem_undo is rcu-protected, on success, the function |
| * performs a rcu_read_lock(). |
| */ |
| static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) |
| { |
| struct sem_array *sma; |
| struct sem_undo_list *ulp; |
| struct sem_undo *un, *new; |
| int nsems, error; |
| |
| error = get_undo_list(&ulp); |
| if (error) |
| return ERR_PTR(error); |
| |
| rcu_read_lock(); |
| spin_lock(&ulp->lock); |
| un = lookup_undo(ulp, semid); |
| spin_unlock(&ulp->lock); |
| if (likely(un != NULL)) |
| goto out; |
| |
| /* no undo structure around - allocate one. */ |
| /* step 1: figure out the size of the semaphore array */ |
| sma = sem_obtain_object_check(ns, semid); |
| if (IS_ERR(sma)) { |
| rcu_read_unlock(); |
| return ERR_CAST(sma); |
| } |
| |
| nsems = sma->sem_nsems; |
| if (!ipc_rcu_getref(&sma->sem_perm)) { |
| rcu_read_unlock(); |
| un = ERR_PTR(-EIDRM); |
| goto out; |
| } |
| rcu_read_unlock(); |
| |
| /* step 2: allocate new undo structure */ |
| new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); |
| if (!new) { |
| ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| return ERR_PTR(-ENOMEM); |
| } |
| |
| /* step 3: Acquire the lock on semaphore array */ |
| rcu_read_lock(); |
| sem_lock_and_putref(sma); |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| kfree(new); |
| un = ERR_PTR(-EIDRM); |
| goto out; |
| } |
| spin_lock(&ulp->lock); |
| |
| /* |
| * step 4: check for races: did someone else allocate the undo struct? |
| */ |
| un = lookup_undo(ulp, semid); |
| if (un) { |
| kfree(new); |
| goto success; |
| } |
| /* step 5: initialize & link new undo structure */ |
| new->semadj = (short *) &new[1]; |
| new->ulp = ulp; |
| new->semid = semid; |
| assert_spin_locked(&ulp->lock); |
| list_add_rcu(&new->list_proc, &ulp->list_proc); |
| ipc_assert_locked_object(&sma->sem_perm); |
| list_add(&new->list_id, &sma->list_id); |
| un = new; |
| |
| success: |
| spin_unlock(&ulp->lock); |
| sem_unlock(sma, -1); |
| out: |
| return un; |
| } |
| |
| static long do_semtimedop(int semid, struct sembuf __user *tsops, |
| unsigned nsops, const struct timespec64 *timeout) |
| { |
| int error = -EINVAL; |
| struct sem_array *sma; |
| struct sembuf fast_sops[SEMOPM_FAST]; |
| struct sembuf *sops = fast_sops, *sop; |
| struct sem_undo *un; |
| int max, locknum; |
| bool undos = false, alter = false, dupsop = false; |
| struct sem_queue queue; |
| unsigned long dup = 0, jiffies_left = 0; |
| struct ipc_namespace *ns; |
| |
| ns = current->nsproxy->ipc_ns; |
| |
| if (nsops < 1 || semid < 0) |
| return -EINVAL; |
| if (nsops > ns->sc_semopm) |
| return -E2BIG; |
| if (nsops > SEMOPM_FAST) { |
| sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL); |
| if (sops == NULL) |
| return -ENOMEM; |
| } |
| |
| if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) { |
| error = -EFAULT; |
| goto out_free; |
| } |
| |
| if (timeout) { |
| if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 || |
| timeout->tv_nsec >= 1000000000L) { |
| error = -EINVAL; |
| goto out_free; |
| } |
| jiffies_left = timespec64_to_jiffies(timeout); |
| } |
| |
| max = 0; |
| for (sop = sops; sop < sops + nsops; sop++) { |
| unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG); |
| |
| if (sop->sem_num >= max) |
| max = sop->sem_num; |
| if (sop->sem_flg & SEM_UNDO) |
| undos = true; |
| if (dup & mask) { |
| /* |
| * There was a previous alter access that appears |
| * to have accessed the same semaphore, thus use |
| * the dupsop logic. "appears", because the detection |
| * can only check % BITS_PER_LONG. |
| */ |
| dupsop = true; |
| } |
| if (sop->sem_op != 0) { |
| alter = true; |
| dup |= mask; |
| } |
| } |
| |
| if (undos) { |
| /* On success, find_alloc_undo takes the rcu_read_lock */ |
| un = find_alloc_undo(ns, semid); |
| if (IS_ERR(un)) { |
| error = PTR_ERR(un); |
| goto out_free; |
| } |
| } else { |
| un = NULL; |
| rcu_read_lock(); |
| } |
| |
| sma = sem_obtain_object_check(ns, semid); |
| if (IS_ERR(sma)) { |
| rcu_read_unlock(); |
| error = PTR_ERR(sma); |
| goto out_free; |
| } |
| |
| error = -EFBIG; |
| if (max >= sma->sem_nsems) { |
| rcu_read_unlock(); |
| goto out_free; |
| } |
| |
| error = -EACCES; |
| if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) { |
| rcu_read_unlock(); |
| goto out_free; |
| } |
| |
| error = security_sem_semop(&sma->sem_perm, sops, nsops, alter); |
| if (error) { |
| rcu_read_unlock(); |
| goto out_free; |
| } |
| |
| error = -EIDRM; |
| locknum = sem_lock(sma, sops, nsops); |
| /* |
| * We eventually might perform the following check in a lockless |
| * fashion, considering ipc_valid_object() locking constraints. |
| * If nsops == 1 and there is no contention for sem_perm.lock, then |
| * only a per-semaphore lock is held and it's OK to proceed with the |
| * check below. More details on the fine grained locking scheme |
| * entangled here and why it's RMID race safe on comments at sem_lock() |
| */ |
| if (!ipc_valid_object(&sma->sem_perm)) |
| goto out_unlock_free; |
| /* |
| * semid identifiers are not unique - find_alloc_undo may have |
| * allocated an undo structure, it was invalidated by an RMID |
| * and now a new array with received the same id. Check and fail. |
| * This case can be detected checking un->semid. The existence of |
| * "un" itself is guaranteed by rcu. |
| */ |
| if (un && un->semid == -1) |
| goto out_unlock_free; |
| |
| queue.sops = sops; |
| queue.nsops = nsops; |
| queue.undo = un; |
| queue.pid = task_tgid(current); |
| queue.alter = alter; |
| queue.dupsop = dupsop; |
| |
| error = perform_atomic_semop(sma, &queue); |
| if (error == 0) { /* non-blocking succesfull path */ |
| DEFINE_WAKE_Q(wake_q); |
| |
| /* |
| * If the operation was successful, then do |
| * the required updates. |
| */ |
| if (alter) |
| do_smart_update(sma, sops, nsops, 1, &wake_q); |
| else |
| set_semotime(sma, sops); |
| |
| sem_unlock(sma, locknum); |
| rcu_read_unlock(); |
| wake_up_q(&wake_q); |
| |
| goto out_free; |
| } |
| if (error < 0) /* non-blocking error path */ |
| goto out_unlock_free; |
| |
| /* |
| * We need to sleep on this operation, so we put the current |
| * task into the pending queue and go to sleep. |
| */ |
| if (nsops == 1) { |
| struct sem *curr; |
| int idx = array_index_nospec(sops->sem_num, sma->sem_nsems); |
| curr = &sma->sems[idx]; |
| |
| if (alter) { |
| if (sma->complex_count) { |
| list_add_tail(&queue.list, |
| &sma->pending_alter); |
| } else { |
| |
| list_add_tail(&queue.list, |
| &curr->pending_alter); |
| } |
| } else { |
| list_add_tail(&queue.list, &curr->pending_const); |
| } |
| } else { |
| if (!sma->complex_count) |
| merge_queues(sma); |
| |
| if (alter) |
| list_add_tail(&queue.list, &sma->pending_alter); |
| else |
| list_add_tail(&queue.list, &sma->pending_const); |
| |
| sma->complex_count++; |
| } |
| |
| do { |
| WRITE_ONCE(queue.status, -EINTR); |
| queue.sleeper = current; |
| |
| __set_current_state(TASK_INTERRUPTIBLE); |
| sem_unlock(sma, locknum); |
| rcu_read_unlock(); |
| |
| if (timeout) |
| jiffies_left = schedule_timeout(jiffies_left); |
| else |
| schedule(); |
| |
| /* |
| * fastpath: the semop has completed, either successfully or |
| * not, from the syscall pov, is quite irrelevant to us at this |
| * point; we're done. |
| * |
| * We _do_ care, nonetheless, about being awoken by a signal or |
| * spuriously. The queue.status is checked again in the |
| * slowpath (aka after taking sem_lock), such that we can detect |
| * scenarios where we were awakened externally, during the |
| * window between wake_q_add() and wake_up_q(). |
| */ |
| error = READ_ONCE(queue.status); |
| if (error != -EINTR) { |
| /* |
| * User space could assume that semop() is a memory |
| * barrier: Without the mb(), the cpu could |
| * speculatively read in userspace stale data that was |
| * overwritten by the previous owner of the semaphore. |
| */ |
| smp_mb(); |
| goto out_free; |
| } |
| |
| rcu_read_lock(); |
| locknum = sem_lock(sma, sops, nsops); |
| |
| if (!ipc_valid_object(&sma->sem_perm)) |
| goto out_unlock_free; |
| |
| error = READ_ONCE(queue.status); |
| |
| /* |
| * If queue.status != -EINTR we are woken up by another process. |
| * Leave without unlink_queue(), but with sem_unlock(). |
| */ |
| if (error != -EINTR) |
| goto out_unlock_free; |
| |
| /* |
| * If an interrupt occurred we have to clean up the queue. |
| */ |
| if (timeout && jiffies_left == 0) |
| error = -EAGAIN; |
| } while (error == -EINTR && !signal_pending(current)); /* spurious */ |
| |
| unlink_queue(sma, &queue); |
| |
| out_unlock_free: |
| sem_unlock(sma, locknum); |
| rcu_read_unlock(); |
| out_free: |
| if (sops != fast_sops) |
| kvfree(sops); |
| return error; |
| } |
| |
| long ksys_semtimedop(int semid, struct sembuf __user *tsops, |
| unsigned int nsops, const struct __kernel_timespec __user *timeout) |
| { |
| if (timeout) { |
| struct timespec64 ts; |
| if (get_timespec64(&ts, timeout)) |
| return -EFAULT; |
| return do_semtimedop(semid, tsops, nsops, &ts); |
| } |
| return do_semtimedop(semid, tsops, nsops, NULL); |
| } |
| |
| SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, |
| unsigned int, nsops, const struct __kernel_timespec __user *, timeout) |
| { |
| return ksys_semtimedop(semid, tsops, nsops, timeout); |
| } |
| |
| #ifdef CONFIG_COMPAT_32BIT_TIME |
| long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems, |
| unsigned int nsops, |
| const struct old_timespec32 __user *timeout) |
| { |
| if (timeout) { |
| struct timespec64 ts; |
| if (get_old_timespec32(&ts, timeout)) |
| return -EFAULT; |
| return do_semtimedop(semid, tsems, nsops, &ts); |
| } |
| return do_semtimedop(semid, tsems, nsops, NULL); |
| } |
| |
| COMPAT_SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsems, |
| unsigned int, nsops, |
| const struct old_timespec32 __user *, timeout) |
| { |
| return compat_ksys_semtimedop(semid, tsems, nsops, timeout); |
| } |
| #endif |
| |
| SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, |
| unsigned, nsops) |
| { |
| return do_semtimedop(semid, tsops, nsops, NULL); |
| } |
| |
| /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between |
| * parent and child tasks. |
| */ |
| |
| int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) |
| { |
| struct sem_undo_list *undo_list; |
| int error; |
| |
| if (clone_flags & CLONE_SYSVSEM) { |
| error = get_undo_list(&undo_list); |
| if (error) |
| return error; |
| refcount_inc(&undo_list->refcnt); |
| tsk->sysvsem.undo_list = undo_list; |
| } else |
| tsk->sysvsem.undo_list = NULL; |
| |
| return 0; |
| } |
| |
| /* |
| * add semadj values to semaphores, free undo structures. |
| * undo structures are not freed when semaphore arrays are destroyed |
| * so some of them may be out of date. |
| * IMPLEMENTATION NOTE: There is some confusion over whether the |
| * set of adjustments that needs to be done should be done in an atomic |
| * manner or not. That is, if we are attempting to decrement the semval |
| * should we queue up and wait until we can do so legally? |
| * The original implementation attempted to do this (queue and wait). |
| * The current implementation does not do so. The POSIX standard |
| * and SVID should be consulted to determine what behavior is mandated. |
| */ |
| void exit_sem(struct task_struct *tsk) |
| { |
| struct sem_undo_list *ulp; |
| |
| ulp = tsk->sysvsem.undo_list; |
| if (!ulp) |
| return; |
| tsk->sysvsem.undo_list = NULL; |
| |
| if (!refcount_dec_and_test(&ulp->refcnt)) |
| return; |
| |
| for (;;) { |
| struct sem_array *sma; |
| struct sem_undo *un; |
| int semid, i; |
| DEFINE_WAKE_Q(wake_q); |
| |
| cond_resched(); |
| |
| rcu_read_lock(); |
| un = list_entry_rcu(ulp->list_proc.next, |
| struct sem_undo, list_proc); |
| if (&un->list_proc == &ulp->list_proc) { |
| /* |
| * We must wait for freeary() before freeing this ulp, |
| * in case we raced with last sem_undo. There is a small |
| * possibility where we exit while freeary() didn't |
| * finish unlocking sem_undo_list. |
| */ |
| spin_lock(&ulp->lock); |
| spin_unlock(&ulp->lock); |
| rcu_read_unlock(); |
| break; |
| } |
| spin_lock(&ulp->lock); |
| semid = un->semid; |
| spin_unlock(&ulp->lock); |
| |
| /* exit_sem raced with IPC_RMID, nothing to do */ |
| if (semid == -1) { |
| rcu_read_unlock(); |
| continue; |
| } |
| |
| sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid); |
| /* exit_sem raced with IPC_RMID, nothing to do */ |
| if (IS_ERR(sma)) { |
| rcu_read_unlock(); |
| continue; |
| } |
| |
| sem_lock(sma, NULL, -1); |
| /* exit_sem raced with IPC_RMID, nothing to do */ |
| if (!ipc_valid_object(&sma->sem_perm)) { |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| continue; |
| } |
| un = __lookup_undo(ulp, semid); |
| if (un == NULL) { |
| /* exit_sem raced with IPC_RMID+semget() that created |
| * exactly the same semid. Nothing to do. |
| */ |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| continue; |
| } |
| |
| /* remove un from the linked lists */ |
| ipc_assert_locked_object(&sma->sem_perm); |
| list_del(&un->list_id); |
| |
| /* we are the last process using this ulp, acquiring ulp->lock |
| * isn't required. Besides that, we are also protected against |
| * IPC_RMID as we hold sma->sem_perm lock now |
| */ |
| list_del_rcu(&un->list_proc); |
| |
| /* perform adjustments registered in un */ |
| for (i = 0; i < sma->sem_nsems; i++) { |
| struct sem *semaphore = &sma->sems[i]; |
| if (un->semadj[i]) { |
| semaphore->semval += un->semadj[i]; |
| /* |
| * Range checks of the new semaphore value, |
| * not defined by sus: |
| * - Some unices ignore the undo entirely |
| * (e.g. HP UX 11i 11.22, Tru64 V5.1) |
| * - some cap the value (e.g. FreeBSD caps |
| * at 0, but doesn't enforce SEMVMX) |
| * |
| * Linux caps the semaphore value, both at 0 |
| * and at SEMVMX. |
| * |
| * Manfred <manfred@colorfullife.com> |
| */ |
| if (semaphore->semval < 0) |
| semaphore->semval = 0; |
| if (semaphore->semval > SEMVMX) |
| semaphore->semval = SEMVMX; |
| ipc_update_pid(&semaphore->sempid, task_tgid(current)); |
| } |
| } |
| /* maybe some queued-up processes were waiting for this */ |
| do_smart_update(sma, NULL, 0, 1, &wake_q); |
| sem_unlock(sma, -1); |
| rcu_read_unlock(); |
| wake_up_q(&wake_q); |
| |
| kfree_rcu(un, rcu); |
| } |
| kfree(ulp); |
| } |
| |
| #ifdef CONFIG_PROC_FS |
| static int sysvipc_sem_proc_show(struct seq_file *s, void *it) |
| { |
| struct user_namespace *user_ns = seq_user_ns(s); |
| struct kern_ipc_perm *ipcp = it; |
| struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
| time64_t sem_otime; |
| |
| /* |
| * The proc interface isn't aware of sem_lock(), it calls |
| * ipc_lock_object() directly (in sysvipc_find_ipc). |
| * In order to stay compatible with sem_lock(), we must |
| * enter / leave complex_mode. |
| */ |
| complexmode_enter(sma); |
| |
| sem_otime = get_semotime(sma); |
| |
| seq_printf(s, |
| "%10d %10d %4o %10u %5u %5u %5u %5u %10llu %10llu\n", |
| sma->sem_perm.key, |
| sma->sem_perm.id, |
| sma->sem_perm.mode, |
| sma->sem_nsems, |
| from_kuid_munged(user_ns, sma->sem_perm.uid), |
| from_kgid_munged(user_ns, sma->sem_perm.gid), |
| from_kuid_munged(user_ns, sma->sem_perm.cuid), |
| from_kgid_munged(user_ns, sma->sem_perm.cgid), |
| sem_otime, |
| sma->sem_ctime); |
| |
| complexmode_tryleave(sma); |
| |
| return 0; |
| } |
| #endif |