| /* |
| * linux/fs/file.c |
| * |
| * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes |
| * |
| * Manage the dynamic fd arrays in the process files_struct. |
| */ |
| |
| #include <linux/syscalls.h> |
| #include <linux/export.h> |
| #include <linux/fs.h> |
| #include <linux/mm.h> |
| #include <linux/mmzone.h> |
| #include <linux/time.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/vmalloc.h> |
| #include <linux/file.h> |
| #include <linux/fdtable.h> |
| #include <linux/bitops.h> |
| #include <linux/interrupt.h> |
| #include <linux/spinlock.h> |
| #include <linux/rcupdate.h> |
| #include <linux/workqueue.h> |
| |
| struct fdtable_defer { |
| spinlock_t lock; |
| struct work_struct wq; |
| struct fdtable *next; |
| }; |
| |
| int sysctl_nr_open __read_mostly = 1024*1024; |
| int sysctl_nr_open_min = BITS_PER_LONG; |
| int sysctl_nr_open_max = 1024 * 1024; /* raised later */ |
| |
| /* |
| * We use this list to defer free fdtables that have vmalloced |
| * sets/arrays. By keeping a per-cpu list, we avoid having to embed |
| * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in |
| * this per-task structure. |
| */ |
| static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list); |
| |
| static void *alloc_fdmem(size_t size) |
| { |
| /* |
| * Very large allocations can stress page reclaim, so fall back to |
| * vmalloc() if the allocation size will be considered "large" by the VM. |
| */ |
| if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { |
| void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN); |
| if (data != NULL) |
| return data; |
| } |
| return vmalloc(size); |
| } |
| |
| static void free_fdmem(void *ptr) |
| { |
| is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr); |
| } |
| |
| static void __free_fdtable(struct fdtable *fdt) |
| { |
| free_fdmem(fdt->fd); |
| free_fdmem(fdt->open_fds); |
| kfree(fdt); |
| } |
| |
| static void free_fdtable_work(struct work_struct *work) |
| { |
| struct fdtable_defer *f = |
| container_of(work, struct fdtable_defer, wq); |
| struct fdtable *fdt; |
| |
| spin_lock_bh(&f->lock); |
| fdt = f->next; |
| f->next = NULL; |
| spin_unlock_bh(&f->lock); |
| while(fdt) { |
| struct fdtable *next = fdt->next; |
| |
| __free_fdtable(fdt); |
| fdt = next; |
| } |
| } |
| |
| static void free_fdtable_rcu(struct rcu_head *rcu) |
| { |
| struct fdtable *fdt = container_of(rcu, struct fdtable, rcu); |
| struct fdtable_defer *fddef; |
| |
| BUG_ON(!fdt); |
| BUG_ON(fdt->max_fds <= NR_OPEN_DEFAULT); |
| |
| if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) { |
| kfree(fdt->fd); |
| kfree(fdt->open_fds); |
| kfree(fdt); |
| } else { |
| fddef = &get_cpu_var(fdtable_defer_list); |
| spin_lock(&fddef->lock); |
| fdt->next = fddef->next; |
| fddef->next = fdt; |
| /* vmallocs are handled from the workqueue context */ |
| schedule_work(&fddef->wq); |
| spin_unlock(&fddef->lock); |
| put_cpu_var(fdtable_defer_list); |
| } |
| } |
| |
| /* |
| * Expand the fdset in the files_struct. Called with the files spinlock |
| * held for write. |
| */ |
| static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) |
| { |
| unsigned int cpy, set; |
| |
| BUG_ON(nfdt->max_fds < ofdt->max_fds); |
| |
| cpy = ofdt->max_fds * sizeof(struct file *); |
| set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); |
| memcpy(nfdt->fd, ofdt->fd, cpy); |
| memset((char *)(nfdt->fd) + cpy, 0, set); |
| |
| cpy = ofdt->max_fds / BITS_PER_BYTE; |
| set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE; |
| memcpy(nfdt->open_fds, ofdt->open_fds, cpy); |
| memset((char *)(nfdt->open_fds) + cpy, 0, set); |
| memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); |
| memset((char *)(nfdt->close_on_exec) + cpy, 0, set); |
| } |
| |
| static struct fdtable * alloc_fdtable(unsigned int nr) |
| { |
| struct fdtable *fdt; |
| void *data; |
| |
| /* |
| * Figure out how many fds we actually want to support in this fdtable. |
| * Allocation steps are keyed to the size of the fdarray, since it |
| * grows far faster than any of the other dynamic data. We try to fit |
| * the fdarray into comfortable page-tuned chunks: starting at 1024B |
| * and growing in powers of two from there on. |
| */ |
| nr /= (1024 / sizeof(struct file *)); |
| nr = roundup_pow_of_two(nr + 1); |
| nr *= (1024 / sizeof(struct file *)); |
| /* |
| * Note that this can drive nr *below* what we had passed if sysctl_nr_open |
| * had been set lower between the check in expand_files() and here. Deal |
| * with that in caller, it's cheaper that way. |
| * |
| * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise |
| * bitmaps handling below becomes unpleasant, to put it mildly... |
| */ |
| if (unlikely(nr > sysctl_nr_open)) |
| nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; |
| |
| fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL); |
| if (!fdt) |
| goto out; |
| fdt->max_fds = nr; |
| data = alloc_fdmem(nr * sizeof(struct file *)); |
| if (!data) |
| goto out_fdt; |
| fdt->fd = data; |
| |
| data = alloc_fdmem(max_t(size_t, |
| 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); |
| if (!data) |
| goto out_arr; |
| fdt->open_fds = data; |
| data += nr / BITS_PER_BYTE; |
| fdt->close_on_exec = data; |
| fdt->next = NULL; |
| |
| return fdt; |
| |
| out_arr: |
| free_fdmem(fdt->fd); |
| out_fdt: |
| kfree(fdt); |
| out: |
| return NULL; |
| } |
| |
| /* |
| * Expand the file descriptor table. |
| * This function will allocate a new fdtable and both fd array and fdset, of |
| * the given size. |
| * Return <0 error code on error; 1 on successful completion. |
| * The files->file_lock should be held on entry, and will be held on exit. |
| */ |
| static int expand_fdtable(struct files_struct *files, int nr) |
| __releases(files->file_lock) |
| __acquires(files->file_lock) |
| { |
| struct fdtable *new_fdt, *cur_fdt; |
| |
| spin_unlock(&files->file_lock); |
| new_fdt = alloc_fdtable(nr); |
| spin_lock(&files->file_lock); |
| if (!new_fdt) |
| return -ENOMEM; |
| /* |
| * extremely unlikely race - sysctl_nr_open decreased between the check in |
| * caller and alloc_fdtable(). Cheaper to catch it here... |
| */ |
| if (unlikely(new_fdt->max_fds <= nr)) { |
| __free_fdtable(new_fdt); |
| return -EMFILE; |
| } |
| /* |
| * Check again since another task may have expanded the fd table while |
| * we dropped the lock |
| */ |
| cur_fdt = files_fdtable(files); |
| if (nr >= cur_fdt->max_fds) { |
| /* Continue as planned */ |
| copy_fdtable(new_fdt, cur_fdt); |
| rcu_assign_pointer(files->fdt, new_fdt); |
| if (cur_fdt->max_fds > NR_OPEN_DEFAULT) |
| call_rcu(&cur_fdt->rcu, free_fdtable_rcu); |
| } else { |
| /* Somebody else expanded, so undo our attempt */ |
| __free_fdtable(new_fdt); |
| } |
| return 1; |
| } |
| |
| /* |
| * Expand files. |
| * This function will expand the file structures, if the requested size exceeds |
| * the current capacity and there is room for expansion. |
| * Return <0 error code on error; 0 when nothing done; 1 when files were |
| * expanded and execution may have blocked. |
| * The files->file_lock should be held on entry, and will be held on exit. |
| */ |
| static int expand_files(struct files_struct *files, int nr) |
| { |
| struct fdtable *fdt; |
| |
| fdt = files_fdtable(files); |
| |
| /* Do we need to expand? */ |
| if (nr < fdt->max_fds) |
| return 0; |
| |
| /* Can we expand? */ |
| if (nr >= sysctl_nr_open) |
| return -EMFILE; |
| |
| /* All good, so we try */ |
| return expand_fdtable(files, nr); |
| } |
| |
| static inline void __set_close_on_exec(int fd, struct fdtable *fdt) |
| { |
| __set_bit(fd, fdt->close_on_exec); |
| } |
| |
| static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) |
| { |
| __clear_bit(fd, fdt->close_on_exec); |
| } |
| |
| static inline void __set_open_fd(int fd, struct fdtable *fdt) |
| { |
| __set_bit(fd, fdt->open_fds); |
| } |
| |
| static inline void __clear_open_fd(int fd, struct fdtable *fdt) |
| { |
| __clear_bit(fd, fdt->open_fds); |
| } |
| |
| static int count_open_files(struct fdtable *fdt) |
| { |
| int size = fdt->max_fds; |
| int i; |
| |
| /* Find the last open fd */ |
| for (i = size / BITS_PER_LONG; i > 0; ) { |
| if (fdt->open_fds[--i]) |
| break; |
| } |
| i = (i + 1) * BITS_PER_LONG; |
| return i; |
| } |
| |
| /* |
| * Allocate a new files structure and copy contents from the |
| * passed in files structure. |
| * errorp will be valid only when the returned files_struct is NULL. |
| */ |
| struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) |
| { |
| struct files_struct *newf; |
| struct file **old_fds, **new_fds; |
| int open_files, size, i; |
| struct fdtable *old_fdt, *new_fdt; |
| |
| *errorp = -ENOMEM; |
| newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); |
| if (!newf) |
| goto out; |
| |
| atomic_set(&newf->count, 1); |
| |
| spin_lock_init(&newf->file_lock); |
| newf->next_fd = 0; |
| new_fdt = &newf->fdtab; |
| new_fdt->max_fds = NR_OPEN_DEFAULT; |
| new_fdt->close_on_exec = newf->close_on_exec_init; |
| new_fdt->open_fds = newf->open_fds_init; |
| new_fdt->fd = &newf->fd_array[0]; |
| new_fdt->next = NULL; |
| |
| spin_lock(&oldf->file_lock); |
| old_fdt = files_fdtable(oldf); |
| open_files = count_open_files(old_fdt); |
| |
| /* |
| * Check whether we need to allocate a larger fd array and fd set. |
| */ |
| while (unlikely(open_files > new_fdt->max_fds)) { |
| spin_unlock(&oldf->file_lock); |
| |
| if (new_fdt != &newf->fdtab) |
| __free_fdtable(new_fdt); |
| |
| new_fdt = alloc_fdtable(open_files - 1); |
| if (!new_fdt) { |
| *errorp = -ENOMEM; |
| goto out_release; |
| } |
| |
| /* beyond sysctl_nr_open; nothing to do */ |
| if (unlikely(new_fdt->max_fds < open_files)) { |
| __free_fdtable(new_fdt); |
| *errorp = -EMFILE; |
| goto out_release; |
| } |
| |
| /* |
| * Reacquire the oldf lock and a pointer to its fd table |
| * who knows it may have a new bigger fd table. We need |
| * the latest pointer. |
| */ |
| spin_lock(&oldf->file_lock); |
| old_fdt = files_fdtable(oldf); |
| open_files = count_open_files(old_fdt); |
| } |
| |
| old_fds = old_fdt->fd; |
| new_fds = new_fdt->fd; |
| |
| memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8); |
| memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8); |
| |
| for (i = open_files; i != 0; i--) { |
| struct file *f = *old_fds++; |
| if (f) { |
| get_file(f); |
| } else { |
| /* |
| * The fd may be claimed in the fd bitmap but not yet |
| * instantiated in the files array if a sibling thread |
| * is partway through open(). So make sure that this |
| * fd is available to the new process. |
| */ |
| __clear_open_fd(open_files - i, new_fdt); |
| } |
| rcu_assign_pointer(*new_fds++, f); |
| } |
| spin_unlock(&oldf->file_lock); |
| |
| /* compute the remainder to be cleared */ |
| size = (new_fdt->max_fds - open_files) * sizeof(struct file *); |
| |
| /* This is long word aligned thus could use a optimized version */ |
| memset(new_fds, 0, size); |
| |
| if (new_fdt->max_fds > open_files) { |
| int left = (new_fdt->max_fds - open_files) / 8; |
| int start = open_files / BITS_PER_LONG; |
| |
| memset(&new_fdt->open_fds[start], 0, left); |
| memset(&new_fdt->close_on_exec[start], 0, left); |
| } |
| |
| rcu_assign_pointer(newf->fdt, new_fdt); |
| |
| return newf; |
| |
| out_release: |
| kmem_cache_free(files_cachep, newf); |
| out: |
| return NULL; |
| } |
| |
| static void close_files(struct files_struct * files) |
| { |
| int i, j; |
| struct fdtable *fdt; |
| |
| j = 0; |
| |
| /* |
| * It is safe to dereference the fd table without RCU or |
| * ->file_lock because this is the last reference to the |
| * files structure. But use RCU to shut RCU-lockdep up. |
| */ |
| rcu_read_lock(); |
| fdt = files_fdtable(files); |
| rcu_read_unlock(); |
| for (;;) { |
| unsigned long set; |
| i = j * BITS_PER_LONG; |
| if (i >= fdt->max_fds) |
| break; |
| set = fdt->open_fds[j++]; |
| while (set) { |
| if (set & 1) { |
| struct file * file = xchg(&fdt->fd[i], NULL); |
| if (file) { |
| filp_close(file, files); |
| cond_resched(); |
| } |
| } |
| i++; |
| set >>= 1; |
| } |
| } |
| } |
| |
| struct files_struct *get_files_struct(struct task_struct *task) |
| { |
| struct files_struct *files; |
| |
| task_lock(task); |
| files = task->files; |
| if (files) |
| atomic_inc(&files->count); |
| task_unlock(task); |
| |
| return files; |
| } |
| |
| void put_files_struct(struct files_struct *files) |
| { |
| struct fdtable *fdt; |
| |
| if (atomic_dec_and_test(&files->count)) { |
| close_files(files); |
| /* not really needed, since nobody can see us */ |
| rcu_read_lock(); |
| fdt = files_fdtable(files); |
| rcu_read_unlock(); |
| /* free the arrays if they are not embedded */ |
| if (fdt != &files->fdtab) |
| __free_fdtable(fdt); |
| kmem_cache_free(files_cachep, files); |
| } |
| } |
| |
| void reset_files_struct(struct files_struct *files) |
| { |
| struct task_struct *tsk = current; |
| struct files_struct *old; |
| |
| old = tsk->files; |
| task_lock(tsk); |
| tsk->files = files; |
| task_unlock(tsk); |
| put_files_struct(old); |
| } |
| |
| void exit_files(struct task_struct *tsk) |
| { |
| struct files_struct * files = tsk->files; |
| |
| if (files) { |
| task_lock(tsk); |
| tsk->files = NULL; |
| task_unlock(tsk); |
| put_files_struct(files); |
| } |
| } |
| |
| static void __devinit fdtable_defer_list_init(int cpu) |
| { |
| struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu); |
| spin_lock_init(&fddef->lock); |
| INIT_WORK(&fddef->wq, free_fdtable_work); |
| fddef->next = NULL; |
| } |
| |
| void __init files_defer_init(void) |
| { |
| int i; |
| for_each_possible_cpu(i) |
| fdtable_defer_list_init(i); |
| sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) & |
| -BITS_PER_LONG; |
| } |
| |
| struct files_struct init_files = { |
| .count = ATOMIC_INIT(1), |
| .fdt = &init_files.fdtab, |
| .fdtab = { |
| .max_fds = NR_OPEN_DEFAULT, |
| .fd = &init_files.fd_array[0], |
| .close_on_exec = init_files.close_on_exec_init, |
| .open_fds = init_files.open_fds_init, |
| }, |
| .file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock), |
| }; |
| |
| /* |
| * allocate a file descriptor, mark it busy. |
| */ |
| int __alloc_fd(struct files_struct *files, |
| unsigned start, unsigned end, unsigned flags) |
| { |
| unsigned int fd; |
| int error; |
| struct fdtable *fdt; |
| |
| spin_lock(&files->file_lock); |
| repeat: |
| fdt = files_fdtable(files); |
| fd = start; |
| if (fd < files->next_fd) |
| fd = files->next_fd; |
| |
| if (fd < fdt->max_fds) |
| fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); |
| |
| /* |
| * N.B. For clone tasks sharing a files structure, this test |
| * will limit the total number of files that can be opened. |
| */ |
| error = -EMFILE; |
| if (fd >= end) |
| goto out; |
| |
| error = expand_files(files, fd); |
| if (error < 0) |
| goto out; |
| |
| /* |
| * If we needed to expand the fs array we |
| * might have blocked - try again. |
| */ |
| if (error) |
| goto repeat; |
| |
| if (start <= files->next_fd) |
| files->next_fd = fd + 1; |
| |
| __set_open_fd(fd, fdt); |
| if (flags & O_CLOEXEC) |
| __set_close_on_exec(fd, fdt); |
| else |
| __clear_close_on_exec(fd, fdt); |
| error = fd; |
| #if 1 |
| /* Sanity check */ |
| if (rcu_dereference_raw(fdt->fd[fd]) != NULL) { |
| printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); |
| rcu_assign_pointer(fdt->fd[fd], NULL); |
| } |
| #endif |
| |
| out: |
| spin_unlock(&files->file_lock); |
| return error; |
| } |
| |
| static int alloc_fd(unsigned start, unsigned flags) |
| { |
| return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags); |
| } |
| |
| int get_unused_fd_flags(unsigned flags) |
| { |
| return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags); |
| } |
| EXPORT_SYMBOL(get_unused_fd_flags); |
| |
| static void __put_unused_fd(struct files_struct *files, unsigned int fd) |
| { |
| struct fdtable *fdt = files_fdtable(files); |
| __clear_open_fd(fd, fdt); |
| if (fd < files->next_fd) |
| files->next_fd = fd; |
| } |
| |
| void put_unused_fd(unsigned int fd) |
| { |
| struct files_struct *files = current->files; |
| spin_lock(&files->file_lock); |
| __put_unused_fd(files, fd); |
| spin_unlock(&files->file_lock); |
| } |
| |
| EXPORT_SYMBOL(put_unused_fd); |
| |
| /* |
| * Install a file pointer in the fd array. |
| * |
| * The VFS is full of places where we drop the files lock between |
| * setting the open_fds bitmap and installing the file in the file |
| * array. At any such point, we are vulnerable to a dup2() race |
| * installing a file in the array before us. We need to detect this and |
| * fput() the struct file we are about to overwrite in this case. |
| * |
| * It should never happen - if we allow dup2() do it, _really_ bad things |
| * will follow. |
| * |
| * NOTE: __fd_install() variant is really, really low-level; don't |
| * use it unless you are forced to by truly lousy API shoved down |
| * your throat. 'files' *MUST* be either current->files or obtained |
| * by get_files_struct(current) done by whoever had given it to you, |
| * or really bad things will happen. Normally you want to use |
| * fd_install() instead. |
| */ |
| |
| void __fd_install(struct files_struct *files, unsigned int fd, |
| struct file *file) |
| { |
| struct fdtable *fdt; |
| spin_lock(&files->file_lock); |
| fdt = files_fdtable(files); |
| BUG_ON(fdt->fd[fd] != NULL); |
| rcu_assign_pointer(fdt->fd[fd], file); |
| spin_unlock(&files->file_lock); |
| } |
| |
| void fd_install(unsigned int fd, struct file *file) |
| { |
| __fd_install(current->files, fd, file); |
| } |
| |
| EXPORT_SYMBOL(fd_install); |
| |
| /* |
| * The same warnings as for __alloc_fd()/__fd_install() apply here... |
| */ |
| int __close_fd(struct files_struct *files, unsigned fd) |
| { |
| struct file *file; |
| struct fdtable *fdt; |
| |
| spin_lock(&files->file_lock); |
| fdt = files_fdtable(files); |
| if (fd >= fdt->max_fds) |
| goto out_unlock; |
| file = fdt->fd[fd]; |
| if (!file) |
| goto out_unlock; |
| rcu_assign_pointer(fdt->fd[fd], NULL); |
| __clear_close_on_exec(fd, fdt); |
| __put_unused_fd(files, fd); |
| spin_unlock(&files->file_lock); |
| return filp_close(file, files); |
| |
| out_unlock: |
| spin_unlock(&files->file_lock); |
| return -EBADF; |
| } |
| |
| void do_close_on_exec(struct files_struct *files) |
| { |
| unsigned i; |
| struct fdtable *fdt; |
| |
| /* exec unshares first */ |
| BUG_ON(atomic_read(&files->count) != 1); |
| spin_lock(&files->file_lock); |
| for (i = 0; ; i++) { |
| unsigned long set; |
| unsigned fd = i * BITS_PER_LONG; |
| fdt = files_fdtable(files); |
| if (fd >= fdt->max_fds) |
| break; |
| set = fdt->close_on_exec[i]; |
| if (!set) |
| continue; |
| fdt->close_on_exec[i] = 0; |
| for ( ; set ; fd++, set >>= 1) { |
| struct file *file; |
| if (!(set & 1)) |
| continue; |
| file = fdt->fd[fd]; |
| if (!file) |
| continue; |
| rcu_assign_pointer(fdt->fd[fd], NULL); |
| __put_unused_fd(files, fd); |
| spin_unlock(&files->file_lock); |
| filp_close(file, files); |
| cond_resched(); |
| spin_lock(&files->file_lock); |
| } |
| |
| } |
| spin_unlock(&files->file_lock); |
| } |
| |
| struct file *fget(unsigned int fd) |
| { |
| struct file *file; |
| struct files_struct *files = current->files; |
| |
| rcu_read_lock(); |
| file = fcheck_files(files, fd); |
| if (file) { |
| /* File object ref couldn't be taken */ |
| if (file->f_mode & FMODE_PATH || |
| !atomic_long_inc_not_zero(&file->f_count)) |
| file = NULL; |
| } |
| rcu_read_unlock(); |
| |
| return file; |
| } |
| |
| EXPORT_SYMBOL(fget); |
| |
| struct file *fget_raw(unsigned int fd) |
| { |
| struct file *file; |
| struct files_struct *files = current->files; |
| |
| rcu_read_lock(); |
| file = fcheck_files(files, fd); |
| if (file) { |
| /* File object ref couldn't be taken */ |
| if (!atomic_long_inc_not_zero(&file->f_count)) |
| file = NULL; |
| } |
| rcu_read_unlock(); |
| |
| return file; |
| } |
| |
| EXPORT_SYMBOL(fget_raw); |
| |
| /* |
| * Lightweight file lookup - no refcnt increment if fd table isn't shared. |
| * |
| * You can use this instead of fget if you satisfy all of the following |
| * conditions: |
| * 1) You must call fput_light before exiting the syscall and returning control |
| * to userspace (i.e. you cannot remember the returned struct file * after |
| * returning to userspace). |
| * 2) You must not call filp_close on the returned struct file * in between |
| * calls to fget_light and fput_light. |
| * 3) You must not clone the current task in between the calls to fget_light |
| * and fput_light. |
| * |
| * The fput_needed flag returned by fget_light should be passed to the |
| * corresponding fput_light. |
| */ |
| struct file *fget_light(unsigned int fd, int *fput_needed) |
| { |
| struct file *file; |
| struct files_struct *files = current->files; |
| |
| *fput_needed = 0; |
| if (atomic_read(&files->count) == 1) { |
| file = fcheck_files(files, fd); |
| if (file && (file->f_mode & FMODE_PATH)) |
| file = NULL; |
| } else { |
| rcu_read_lock(); |
| file = fcheck_files(files, fd); |
| if (file) { |
| if (!(file->f_mode & FMODE_PATH) && |
| atomic_long_inc_not_zero(&file->f_count)) |
| *fput_needed = 1; |
| else |
| /* Didn't get the reference, someone's freed */ |
| file = NULL; |
| } |
| rcu_read_unlock(); |
| } |
| |
| return file; |
| } |
| |
| struct file *fget_raw_light(unsigned int fd, int *fput_needed) |
| { |
| struct file *file; |
| struct files_struct *files = current->files; |
| |
| *fput_needed = 0; |
| if (atomic_read(&files->count) == 1) { |
| file = fcheck_files(files, fd); |
| } else { |
| rcu_read_lock(); |
| file = fcheck_files(files, fd); |
| if (file) { |
| if (atomic_long_inc_not_zero(&file->f_count)) |
| *fput_needed = 1; |
| else |
| /* Didn't get the reference, someone's freed */ |
| file = NULL; |
| } |
| rcu_read_unlock(); |
| } |
| |
| return file; |
| } |
| |
| void set_close_on_exec(unsigned int fd, int flag) |
| { |
| struct files_struct *files = current->files; |
| struct fdtable *fdt; |
| spin_lock(&files->file_lock); |
| fdt = files_fdtable(files); |
| if (flag) |
| __set_close_on_exec(fd, fdt); |
| else |
| __clear_close_on_exec(fd, fdt); |
| spin_unlock(&files->file_lock); |
| } |
| |
| bool get_close_on_exec(unsigned int fd) |
| { |
| struct files_struct *files = current->files; |
| struct fdtable *fdt; |
| bool res; |
| rcu_read_lock(); |
| fdt = files_fdtable(files); |
| res = close_on_exec(fd, fdt); |
| rcu_read_unlock(); |
| return res; |
| } |
| |
| static int do_dup2(struct files_struct *files, |
| struct file *file, unsigned fd, unsigned flags) |
| { |
| struct file *tofree; |
| struct fdtable *fdt; |
| |
| /* |
| * We need to detect attempts to do dup2() over allocated but still |
| * not finished descriptor. NB: OpenBSD avoids that at the price of |
| * extra work in their equivalent of fget() - they insert struct |
| * file immediately after grabbing descriptor, mark it larval if |
| * more work (e.g. actual opening) is needed and make sure that |
| * fget() treats larval files as absent. Potentially interesting, |
| * but while extra work in fget() is trivial, locking implications |
| * and amount of surgery on open()-related paths in VFS are not. |
| * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" |
| * deadlocks in rather amusing ways, AFAICS. All of that is out of |
| * scope of POSIX or SUS, since neither considers shared descriptor |
| * tables and this condition does not arise without those. |
| */ |
| fdt = files_fdtable(files); |
| tofree = fdt->fd[fd]; |
| if (!tofree && fd_is_open(fd, fdt)) |
| goto Ebusy; |
| get_file(file); |
| rcu_assign_pointer(fdt->fd[fd], file); |
| __set_open_fd(fd, fdt); |
| if (flags & O_CLOEXEC) |
| __set_close_on_exec(fd, fdt); |
| else |
| __clear_close_on_exec(fd, fdt); |
| spin_unlock(&files->file_lock); |
| |
| if (tofree) |
| filp_close(tofree, files); |
| |
| return fd; |
| |
| Ebusy: |
| spin_unlock(&files->file_lock); |
| return -EBUSY; |
| } |
| |
| int replace_fd(unsigned fd, struct file *file, unsigned flags) |
| { |
| int err; |
| struct files_struct *files = current->files; |
| |
| if (!file) |
| return __close_fd(files, fd); |
| |
| if (fd >= rlimit(RLIMIT_NOFILE)) |
| return -EMFILE; |
| |
| spin_lock(&files->file_lock); |
| err = expand_files(files, fd); |
| if (unlikely(err < 0)) |
| goto out_unlock; |
| return do_dup2(files, file, fd, flags); |
| |
| out_unlock: |
| spin_unlock(&files->file_lock); |
| return err; |
| } |
| |
| SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) |
| { |
| int err = -EBADF; |
| struct file *file; |
| struct files_struct *files = current->files; |
| |
| if ((flags & ~O_CLOEXEC) != 0) |
| return -EINVAL; |
| |
| if (newfd >= rlimit(RLIMIT_NOFILE)) |
| return -EMFILE; |
| |
| spin_lock(&files->file_lock); |
| err = expand_files(files, newfd); |
| file = fcheck(oldfd); |
| if (unlikely(!file)) |
| goto Ebadf; |
| if (unlikely(err < 0)) { |
| if (err == -EMFILE) |
| goto Ebadf; |
| goto out_unlock; |
| } |
| return do_dup2(files, file, newfd, flags); |
| |
| Ebadf: |
| err = -EBADF; |
| out_unlock: |
| spin_unlock(&files->file_lock); |
| return err; |
| } |
| |
| SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) |
| { |
| if (unlikely(newfd == oldfd)) { /* corner case */ |
| struct files_struct *files = current->files; |
| int retval = oldfd; |
| |
| rcu_read_lock(); |
| if (!fcheck_files(files, oldfd)) |
| retval = -EBADF; |
| rcu_read_unlock(); |
| return retval; |
| } |
| return sys_dup3(oldfd, newfd, 0); |
| } |
| |
| SYSCALL_DEFINE1(dup, unsigned int, fildes) |
| { |
| int ret = -EBADF; |
| struct file *file = fget_raw(fildes); |
| |
| if (file) { |
| ret = get_unused_fd(); |
| if (ret >= 0) |
| fd_install(ret, file); |
| else |
| fput(file); |
| } |
| return ret; |
| } |
| |
| int f_dupfd(unsigned int from, struct file *file, unsigned flags) |
| { |
| int err; |
| if (from >= rlimit(RLIMIT_NOFILE)) |
| return -EINVAL; |
| err = alloc_fd(from, flags); |
| if (err >= 0) { |
| get_file(file); |
| fd_install(err, file); |
| } |
| return err; |
| } |