| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * fs/userfaultfd.c |
| * |
| * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> |
| * Copyright (C) 2008-2009 Red Hat, Inc. |
| * Copyright (C) 2015 Red Hat, Inc. |
| * |
| * Some part derived from fs/eventfd.c (anon inode setup) and |
| * mm/ksm.c (mm hashing). |
| */ |
| |
| #include <linux/list.h> |
| #include <linux/hashtable.h> |
| #include <linux/sched/signal.h> |
| #include <linux/sched/mm.h> |
| #include <linux/mm.h> |
| #include <linux/poll.h> |
| #include <linux/slab.h> |
| #include <linux/seq_file.h> |
| #include <linux/file.h> |
| #include <linux/bug.h> |
| #include <linux/anon_inodes.h> |
| #include <linux/syscalls.h> |
| #include <linux/userfaultfd_k.h> |
| #include <linux/mempolicy.h> |
| #include <linux/ioctl.h> |
| #include <linux/security.h> |
| #include <linux/hugetlb.h> |
| |
| int sysctl_unprivileged_userfaultfd __read_mostly = 1; |
| |
| static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
| |
| enum userfaultfd_state { |
| UFFD_STATE_WAIT_API, |
| UFFD_STATE_RUNNING, |
| }; |
| |
| /* |
| * Start with fault_pending_wqh and fault_wqh so they're more likely |
| * to be in the same cacheline. |
| * |
| * Locking order: |
| * fd_wqh.lock |
| * fault_pending_wqh.lock |
| * fault_wqh.lock |
| * event_wqh.lock |
| * |
| * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, |
| * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's |
| * also taken in IRQ context. |
| */ |
| struct userfaultfd_ctx { |
| /* waitqueue head for the pending (i.e. not read) userfaults */ |
| wait_queue_head_t fault_pending_wqh; |
| /* waitqueue head for the userfaults */ |
| wait_queue_head_t fault_wqh; |
| /* waitqueue head for the pseudo fd to wakeup poll/read */ |
| wait_queue_head_t fd_wqh; |
| /* waitqueue head for events */ |
| wait_queue_head_t event_wqh; |
| /* a refile sequence protected by fault_pending_wqh lock */ |
| struct seqcount refile_seq; |
| /* pseudo fd refcounting */ |
| refcount_t refcount; |
| /* userfaultfd syscall flags */ |
| unsigned int flags; |
| /* features requested from the userspace */ |
| unsigned int features; |
| /* state machine */ |
| enum userfaultfd_state state; |
| /* released */ |
| bool released; |
| /* memory mappings are changing because of non-cooperative event */ |
| bool mmap_changing; |
| /* mm with one ore more vmas attached to this userfaultfd_ctx */ |
| struct mm_struct *mm; |
| }; |
| |
| struct userfaultfd_fork_ctx { |
| struct userfaultfd_ctx *orig; |
| struct userfaultfd_ctx *new; |
| struct list_head list; |
| }; |
| |
| struct userfaultfd_unmap_ctx { |
| struct userfaultfd_ctx *ctx; |
| unsigned long start; |
| unsigned long end; |
| struct list_head list; |
| }; |
| |
| struct userfaultfd_wait_queue { |
| struct uffd_msg msg; |
| wait_queue_entry_t wq; |
| struct userfaultfd_ctx *ctx; |
| bool waken; |
| }; |
| |
| struct userfaultfd_wake_range { |
| unsigned long start; |
| unsigned long len; |
| }; |
| |
| static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, |
| int wake_flags, void *key) |
| { |
| struct userfaultfd_wake_range *range = key; |
| int ret; |
| struct userfaultfd_wait_queue *uwq; |
| unsigned long start, len; |
| |
| uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| ret = 0; |
| /* len == 0 means wake all */ |
| start = range->start; |
| len = range->len; |
| if (len && (start > uwq->msg.arg.pagefault.address || |
| start + len <= uwq->msg.arg.pagefault.address)) |
| goto out; |
| WRITE_ONCE(uwq->waken, true); |
| /* |
| * The Program-Order guarantees provided by the scheduler |
| * ensure uwq->waken is visible before the task is woken. |
| */ |
| ret = wake_up_state(wq->private, mode); |
| if (ret) { |
| /* |
| * Wake only once, autoremove behavior. |
| * |
| * After the effect of list_del_init is visible to the other |
| * CPUs, the waitqueue may disappear from under us, see the |
| * !list_empty_careful() in handle_userfault(). |
| * |
| * try_to_wake_up() has an implicit smp_mb(), and the |
| * wq->private is read before calling the extern function |
| * "wake_up_state" (which in turns calls try_to_wake_up). |
| */ |
| list_del_init(&wq->entry); |
| } |
| out: |
| return ret; |
| } |
| |
| /** |
| * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd |
| * context. |
| * @ctx: [in] Pointer to the userfaultfd context. |
| */ |
| static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) |
| { |
| refcount_inc(&ctx->refcount); |
| } |
| |
| /** |
| * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd |
| * context. |
| * @ctx: [in] Pointer to userfaultfd context. |
| * |
| * The userfaultfd context reference must have been previously acquired either |
| * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). |
| */ |
| static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) |
| { |
| if (refcount_dec_and_test(&ctx->refcount)) { |
| VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); |
| VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); |
| VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); |
| VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); |
| VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
| VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); |
| VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
| VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); |
| mmdrop(ctx->mm); |
| kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
| } |
| } |
| |
| static inline void msg_init(struct uffd_msg *msg) |
| { |
| BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
| /* |
| * Must use memset to zero out the paddings or kernel data is |
| * leaked to userland. |
| */ |
| memset(msg, 0, sizeof(struct uffd_msg)); |
| } |
| |
| static inline struct uffd_msg userfault_msg(unsigned long address, |
| unsigned int flags, |
| unsigned long reason, |
| unsigned int features) |
| { |
| struct uffd_msg msg; |
| msg_init(&msg); |
| msg.event = UFFD_EVENT_PAGEFAULT; |
| msg.arg.pagefault.address = address; |
| if (flags & FAULT_FLAG_WRITE) |
| /* |
| * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
| * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE |
| * was not set in a UFFD_EVENT_PAGEFAULT, it means it |
| * was a read fault, otherwise if set it means it's |
| * a write fault. |
| */ |
| msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
| if (reason & VM_UFFD_WP) |
| /* |
| * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
| * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was |
| * not set in a UFFD_EVENT_PAGEFAULT, it means it was |
| * a missing fault, otherwise if set it means it's a |
| * write protect fault. |
| */ |
| msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
| if (features & UFFD_FEATURE_THREAD_ID) |
| msg.arg.pagefault.feat.ptid = task_pid_vnr(current); |
| return msg; |
| } |
| |
| #ifdef CONFIG_HUGETLB_PAGE |
| /* |
| * Same functionality as userfaultfd_must_wait below with modifications for |
| * hugepmd ranges. |
| */ |
| static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, |
| struct vm_area_struct *vma, |
| unsigned long address, |
| unsigned long flags, |
| unsigned long reason) |
| { |
| struct mm_struct *mm = ctx->mm; |
| pte_t *ptep, pte; |
| bool ret = true; |
| |
| VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| |
| ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma)); |
| |
| if (!ptep) |
| goto out; |
| |
| ret = false; |
| pte = huge_ptep_get(ptep); |
| |
| /* |
| * Lockless access: we're in a wait_event so it's ok if it |
| * changes under us. |
| */ |
| if (huge_pte_none(pte)) |
| ret = true; |
| if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) |
| ret = true; |
| out: |
| return ret; |
| } |
| #else |
| static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, |
| struct vm_area_struct *vma, |
| unsigned long address, |
| unsigned long flags, |
| unsigned long reason) |
| { |
| return false; /* should never get here */ |
| } |
| #endif /* CONFIG_HUGETLB_PAGE */ |
| |
| /* |
| * Verify the pagetables are still not ok after having reigstered into |
| * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any |
| * userfault that has already been resolved, if userfaultfd_read and |
| * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different |
| * threads. |
| */ |
| static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, |
| unsigned long address, |
| unsigned long flags, |
| unsigned long reason) |
| { |
| struct mm_struct *mm = ctx->mm; |
| pgd_t *pgd; |
| p4d_t *p4d; |
| pud_t *pud; |
| pmd_t *pmd, _pmd; |
| pte_t *pte; |
| bool ret = true; |
| |
| VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); |
| |
| pgd = pgd_offset(mm, address); |
| if (!pgd_present(*pgd)) |
| goto out; |
| p4d = p4d_offset(pgd, address); |
| if (!p4d_present(*p4d)) |
| goto out; |
| pud = pud_offset(p4d, address); |
| if (!pud_present(*pud)) |
| goto out; |
| pmd = pmd_offset(pud, address); |
| /* |
| * READ_ONCE must function as a barrier with narrower scope |
| * and it must be equivalent to: |
| * _pmd = *pmd; barrier(); |
| * |
| * This is to deal with the instability (as in |
| * pmd_trans_unstable) of the pmd. |
| */ |
| _pmd = READ_ONCE(*pmd); |
| if (pmd_none(_pmd)) |
| goto out; |
| |
| ret = false; |
| if (!pmd_present(_pmd)) |
| goto out; |
| |
| if (pmd_trans_huge(_pmd)) |
| goto out; |
| |
| /* |
| * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it |
| * and use the standard pte_offset_map() instead of parsing _pmd. |
| */ |
| pte = pte_offset_map(pmd, address); |
| /* |
| * Lockless access: we're in a wait_event so it's ok if it |
| * changes under us. |
| */ |
| if (pte_none(*pte)) |
| ret = true; |
| pte_unmap(pte); |
| |
| out: |
| return ret; |
| } |
| |
| /* |
| * The locking rules involved in returning VM_FAULT_RETRY depending on |
| * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and |
| * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" |
| * recommendation in __lock_page_or_retry is not an understatement. |
| * |
| * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released |
| * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is |
| * not set. |
| * |
| * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not |
| * set, VM_FAULT_RETRY can still be returned if and only if there are |
| * fatal_signal_pending()s, and the mmap_sem must be released before |
| * returning it. |
| */ |
| vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) |
| { |
| struct mm_struct *mm = vmf->vma->vm_mm; |
| struct userfaultfd_ctx *ctx; |
| struct userfaultfd_wait_queue uwq; |
| vm_fault_t ret = VM_FAULT_SIGBUS; |
| bool must_wait, return_to_userland; |
| long blocking_state; |
| |
| /* |
| * We don't do userfault handling for the final child pid update. |
| * |
| * We also don't do userfault handling during |
| * coredumping. hugetlbfs has the special |
| * follow_hugetlb_page() to skip missing pages in the |
| * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with |
| * the no_page_table() helper in follow_page_mask(), but the |
| * shmem_vm_ops->fault method is invoked even during |
| * coredumping without mmap_sem and it ends up here. |
| */ |
| if (current->flags & (PF_EXITING|PF_DUMPCORE)) |
| goto out; |
| |
| /* |
| * Coredumping runs without mmap_sem so we can only check that |
| * the mmap_sem is held, if PF_DUMPCORE was not set. |
| */ |
| WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem)); |
| |
| ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
| if (!ctx) |
| goto out; |
| |
| BUG_ON(ctx->mm != mm); |
| |
| VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP)); |
| VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP)); |
| |
| if (ctx->features & UFFD_FEATURE_SIGBUS) |
| goto out; |
| |
| /* |
| * If it's already released don't get it. This avoids to loop |
| * in __get_user_pages if userfaultfd_release waits on the |
| * caller of handle_userfault to release the mmap_sem. |
| */ |
| if (unlikely(READ_ONCE(ctx->released))) { |
| /* |
| * Don't return VM_FAULT_SIGBUS in this case, so a non |
| * cooperative manager can close the uffd after the |
| * last UFFDIO_COPY, without risking to trigger an |
| * involuntary SIGBUS if the process was starting the |
| * userfaultfd while the userfaultfd was still armed |
| * (but after the last UFFDIO_COPY). If the uffd |
| * wasn't already closed when the userfault reached |
| * this point, that would normally be solved by |
| * userfaultfd_must_wait returning 'false'. |
| * |
| * If we were to return VM_FAULT_SIGBUS here, the non |
| * cooperative manager would be instead forced to |
| * always call UFFDIO_UNREGISTER before it can safely |
| * close the uffd. |
| */ |
| ret = VM_FAULT_NOPAGE; |
| goto out; |
| } |
| |
| /* |
| * Check that we can return VM_FAULT_RETRY. |
| * |
| * NOTE: it should become possible to return VM_FAULT_RETRY |
| * even if FAULT_FLAG_TRIED is set without leading to gup() |
| * -EBUSY failures, if the userfaultfd is to be extended for |
| * VM_UFFD_WP tracking and we intend to arm the userfault |
| * without first stopping userland access to the memory. For |
| * VM_UFFD_MISSING userfaults this is enough for now. |
| */ |
| if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
| /* |
| * Validate the invariant that nowait must allow retry |
| * to be sure not to return SIGBUS erroneously on |
| * nowait invocations. |
| */ |
| BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
| #ifdef CONFIG_DEBUG_VM |
| if (printk_ratelimit()) { |
| printk(KERN_WARNING |
| "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
| vmf->flags); |
| dump_stack(); |
| } |
| #endif |
| goto out; |
| } |
| |
| /* |
| * Handle nowait, not much to do other than tell it to retry |
| * and wait. |
| */ |
| ret = VM_FAULT_RETRY; |
| if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
| goto out; |
| |
| /* take the reference before dropping the mmap_sem */ |
| userfaultfd_ctx_get(ctx); |
| |
| init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
| uwq.wq.private = current; |
| uwq.msg = userfault_msg(vmf->address, vmf->flags, reason, |
| ctx->features); |
| uwq.ctx = ctx; |
| uwq.waken = false; |
| |
| return_to_userland = |
| (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) == |
| (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE); |
| blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : |
| TASK_KILLABLE; |
| |
| spin_lock_irq(&ctx->fault_pending_wqh.lock); |
| /* |
| * After the __add_wait_queue the uwq is visible to userland |
| * through poll/read(). |
| */ |
| __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
| /* |
| * The smp_mb() after __set_current_state prevents the reads |
| * following the spin_unlock to happen before the list_add in |
| * __add_wait_queue. |
| */ |
| set_current_state(blocking_state); |
| spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
| |
| if (!is_vm_hugetlb_page(vmf->vma)) |
| must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, |
| reason); |
| else |
| must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma, |
| vmf->address, |
| vmf->flags, reason); |
| up_read(&mm->mmap_sem); |
| |
| if (likely(must_wait && !READ_ONCE(ctx->released) && |
| (return_to_userland ? !signal_pending(current) : |
| !fatal_signal_pending(current)))) { |
| wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
| schedule(); |
| ret |= VM_FAULT_MAJOR; |
| |
| /* |
| * False wakeups can orginate even from rwsem before |
| * up_read() however userfaults will wait either for a |
| * targeted wakeup on the specific uwq waitqueue from |
| * wake_userfault() or for signals or for uffd |
| * release. |
| */ |
| while (!READ_ONCE(uwq.waken)) { |
| /* |
| * This needs the full smp_store_mb() |
| * guarantee as the state write must be |
| * visible to other CPUs before reading |
| * uwq.waken from other CPUs. |
| */ |
| set_current_state(blocking_state); |
| if (READ_ONCE(uwq.waken) || |
| READ_ONCE(ctx->released) || |
| (return_to_userland ? signal_pending(current) : |
| fatal_signal_pending(current))) |
| break; |
| schedule(); |
| } |
| } |
| |
| __set_current_state(TASK_RUNNING); |
| |
| if (return_to_userland) { |
| if (signal_pending(current) && |
| !fatal_signal_pending(current)) { |
| /* |
| * If we got a SIGSTOP or SIGCONT and this is |
| * a normal userland page fault, just let |
| * userland return so the signal will be |
| * handled and gdb debugging works. The page |
| * fault code immediately after we return from |
| * this function is going to release the |
| * mmap_sem and it's not depending on it |
| * (unlike gup would if we were not to return |
| * VM_FAULT_RETRY). |
| * |
| * If a fatal signal is pending we still take |
| * the streamlined VM_FAULT_RETRY failure path |
| * and there's no need to retake the mmap_sem |
| * in such case. |
| */ |
| down_read(&mm->mmap_sem); |
| ret = VM_FAULT_NOPAGE; |
| } |
| } |
| |
| /* |
| * Here we race with the list_del; list_add in |
| * userfaultfd_ctx_read(), however because we don't ever run |
| * list_del_init() to refile across the two lists, the prev |
| * and next pointers will never point to self. list_add also |
| * would never let any of the two pointers to point to |
| * self. So list_empty_careful won't risk to see both pointers |
| * pointing to self at any time during the list refile. The |
| * only case where list_del_init() is called is the full |
| * removal in the wake function and there we don't re-list_add |
| * and it's fine not to block on the spinlock. The uwq on this |
| * kernel stack can be released after the list_del_init. |
| */ |
| if (!list_empty_careful(&uwq.wq.entry)) { |
| spin_lock_irq(&ctx->fault_pending_wqh.lock); |
| /* |
| * No need of list_del_init(), the uwq on the stack |
| * will be freed shortly anyway. |
| */ |
| list_del(&uwq.wq.entry); |
| spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
| } |
| |
| /* |
| * ctx may go away after this if the userfault pseudo fd is |
| * already released. |
| */ |
| userfaultfd_ctx_put(ctx); |
| |
| out: |
| return ret; |
| } |
| |
| static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, |
| struct userfaultfd_wait_queue *ewq) |
| { |
| struct userfaultfd_ctx *release_new_ctx; |
| |
| if (WARN_ON_ONCE(current->flags & PF_EXITING)) |
| goto out; |
| |
| ewq->ctx = ctx; |
| init_waitqueue_entry(&ewq->wq, current); |
| release_new_ctx = NULL; |
| |
| spin_lock_irq(&ctx->event_wqh.lock); |
| /* |
| * After the __add_wait_queue the uwq is visible to userland |
| * through poll/read(). |
| */ |
| __add_wait_queue(&ctx->event_wqh, &ewq->wq); |
| for (;;) { |
| set_current_state(TASK_KILLABLE); |
| if (ewq->msg.event == 0) |
| break; |
| if (READ_ONCE(ctx->released) || |
| fatal_signal_pending(current)) { |
| /* |
| * &ewq->wq may be queued in fork_event, but |
| * __remove_wait_queue ignores the head |
| * parameter. It would be a problem if it |
| * didn't. |
| */ |
| __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
| if (ewq->msg.event == UFFD_EVENT_FORK) { |
| struct userfaultfd_ctx *new; |
| |
| new = (struct userfaultfd_ctx *) |
| (unsigned long) |
| ewq->msg.arg.reserved.reserved1; |
| release_new_ctx = new; |
| } |
| break; |
| } |
| |
| spin_unlock_irq(&ctx->event_wqh.lock); |
| |
| wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
| schedule(); |
| |
| spin_lock_irq(&ctx->event_wqh.lock); |
| } |
| __set_current_state(TASK_RUNNING); |
| spin_unlock_irq(&ctx->event_wqh.lock); |
| |
| if (release_new_ctx) { |
| struct vm_area_struct *vma; |
| struct mm_struct *mm = release_new_ctx->mm; |
| |
| /* the various vma->vm_userfaultfd_ctx still points to it */ |
| down_write(&mm->mmap_sem); |
| /* no task can run (and in turn coredump) yet */ |
| VM_WARN_ON(!mmget_still_valid(mm)); |
| for (vma = mm->mmap; vma; vma = vma->vm_next) |
| if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { |
| vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); |
| } |
| up_write(&mm->mmap_sem); |
| |
| userfaultfd_ctx_put(release_new_ctx); |
| } |
| |
| /* |
| * ctx may go away after this if the userfault pseudo fd is |
| * already released. |
| */ |
| out: |
| WRITE_ONCE(ctx->mmap_changing, false); |
| userfaultfd_ctx_put(ctx); |
| } |
| |
| static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, |
| struct userfaultfd_wait_queue *ewq) |
| { |
| ewq->msg.event = 0; |
| wake_up_locked(&ctx->event_wqh); |
| __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
| } |
| |
| int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) |
| { |
| struct userfaultfd_ctx *ctx = NULL, *octx; |
| struct userfaultfd_fork_ctx *fctx; |
| |
| octx = vma->vm_userfaultfd_ctx.ctx; |
| if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { |
| vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); |
| return 0; |
| } |
| |
| list_for_each_entry(fctx, fcs, list) |
| if (fctx->orig == octx) { |
| ctx = fctx->new; |
| break; |
| } |
| |
| if (!ctx) { |
| fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); |
| if (!fctx) |
| return -ENOMEM; |
| |
| ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
| if (!ctx) { |
| kfree(fctx); |
| return -ENOMEM; |
| } |
| |
| refcount_set(&ctx->refcount, 1); |
| ctx->flags = octx->flags; |
| ctx->state = UFFD_STATE_RUNNING; |
| ctx->features = octx->features; |
| ctx->released = false; |
| ctx->mmap_changing = false; |
| ctx->mm = vma->vm_mm; |
| mmgrab(ctx->mm); |
| |
| userfaultfd_ctx_get(octx); |
| WRITE_ONCE(octx->mmap_changing, true); |
| fctx->orig = octx; |
| fctx->new = ctx; |
| list_add_tail(&fctx->list, fcs); |
| } |
| |
| vma->vm_userfaultfd_ctx.ctx = ctx; |
| return 0; |
| } |
| |
| static void dup_fctx(struct userfaultfd_fork_ctx *fctx) |
| { |
| struct userfaultfd_ctx *ctx = fctx->orig; |
| struct userfaultfd_wait_queue ewq; |
| |
| msg_init(&ewq.msg); |
| |
| ewq.msg.event = UFFD_EVENT_FORK; |
| ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; |
| |
| userfaultfd_event_wait_completion(ctx, &ewq); |
| } |
| |
| void dup_userfaultfd_complete(struct list_head *fcs) |
| { |
| struct userfaultfd_fork_ctx *fctx, *n; |
| |
| list_for_each_entry_safe(fctx, n, fcs, list) { |
| dup_fctx(fctx); |
| list_del(&fctx->list); |
| kfree(fctx); |
| } |
| } |
| |
| void mremap_userfaultfd_prep(struct vm_area_struct *vma, |
| struct vm_userfaultfd_ctx *vm_ctx) |
| { |
| struct userfaultfd_ctx *ctx; |
| |
| ctx = vma->vm_userfaultfd_ctx.ctx; |
| |
| if (!ctx) |
| return; |
| |
| if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { |
| vm_ctx->ctx = ctx; |
| userfaultfd_ctx_get(ctx); |
| WRITE_ONCE(ctx->mmap_changing, true); |
| } else { |
| /* Drop uffd context if remap feature not enabled */ |
| vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); |
| } |
| } |
| |
| void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, |
| unsigned long from, unsigned long to, |
| unsigned long len) |
| { |
| struct userfaultfd_ctx *ctx = vm_ctx->ctx; |
| struct userfaultfd_wait_queue ewq; |
| |
| if (!ctx) |
| return; |
| |
| if (to & ~PAGE_MASK) { |
| userfaultfd_ctx_put(ctx); |
| return; |
| } |
| |
| msg_init(&ewq.msg); |
| |
| ewq.msg.event = UFFD_EVENT_REMAP; |
| ewq.msg.arg.remap.from = from; |
| ewq.msg.arg.remap.to = to; |
| ewq.msg.arg.remap.len = len; |
| |
| userfaultfd_event_wait_completion(ctx, &ewq); |
| } |
| |
| bool userfaultfd_remove(struct vm_area_struct *vma, |
| unsigned long start, unsigned long end) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| struct userfaultfd_ctx *ctx; |
| struct userfaultfd_wait_queue ewq; |
| |
| ctx = vma->vm_userfaultfd_ctx.ctx; |
| if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) |
| return true; |
| |
| userfaultfd_ctx_get(ctx); |
| WRITE_ONCE(ctx->mmap_changing, true); |
| up_read(&mm->mmap_sem); |
| |
| msg_init(&ewq.msg); |
| |
| ewq.msg.event = UFFD_EVENT_REMOVE; |
| ewq.msg.arg.remove.start = start; |
| ewq.msg.arg.remove.end = end; |
| |
| userfaultfd_event_wait_completion(ctx, &ewq); |
| |
| return false; |
| } |
| |
| static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, |
| unsigned long start, unsigned long end) |
| { |
| struct userfaultfd_unmap_ctx *unmap_ctx; |
| |
| list_for_each_entry(unmap_ctx, unmaps, list) |
| if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && |
| unmap_ctx->end == end) |
| return true; |
| |
| return false; |
| } |
| |
| int userfaultfd_unmap_prep(struct vm_area_struct *vma, |
| unsigned long start, unsigned long end, |
| struct list_head *unmaps) |
| { |
| for ( ; vma && vma->vm_start < end; vma = vma->vm_next) { |
| struct userfaultfd_unmap_ctx *unmap_ctx; |
| struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; |
| |
| if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || |
| has_unmap_ctx(ctx, unmaps, start, end)) |
| continue; |
| |
| unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); |
| if (!unmap_ctx) |
| return -ENOMEM; |
| |
| userfaultfd_ctx_get(ctx); |
| WRITE_ONCE(ctx->mmap_changing, true); |
| unmap_ctx->ctx = ctx; |
| unmap_ctx->start = start; |
| unmap_ctx->end = end; |
| list_add_tail(&unmap_ctx->list, unmaps); |
| } |
| |
| return 0; |
| } |
| |
| void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) |
| { |
| struct userfaultfd_unmap_ctx *ctx, *n; |
| struct userfaultfd_wait_queue ewq; |
| |
| list_for_each_entry_safe(ctx, n, uf, list) { |
| msg_init(&ewq.msg); |
| |
| ewq.msg.event = UFFD_EVENT_UNMAP; |
| ewq.msg.arg.remove.start = ctx->start; |
| ewq.msg.arg.remove.end = ctx->end; |
| |
| userfaultfd_event_wait_completion(ctx->ctx, &ewq); |
| |
| list_del(&ctx->list); |
| kfree(ctx); |
| } |
| } |
| |
| static int userfaultfd_release(struct inode *inode, struct file *file) |
| { |
| struct userfaultfd_ctx *ctx = file->private_data; |
| struct mm_struct *mm = ctx->mm; |
| struct vm_area_struct *vma, *prev; |
| /* len == 0 means wake all */ |
| struct userfaultfd_wake_range range = { .len = 0, }; |
| unsigned long new_flags; |
| bool still_valid; |
| |
| WRITE_ONCE(ctx->released, true); |
| |
| if (!mmget_not_zero(mm)) |
| goto wakeup; |
| |
| /* |
| * Flush page faults out of all CPUs. NOTE: all page faults |
| * must be retried without returning VM_FAULT_SIGBUS if |
| * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx |
| * changes while handle_userfault released the mmap_sem. So |
| * it's critical that released is set to true (above), before |
| * taking the mmap_sem for writing. |
| */ |
| down_write(&mm->mmap_sem); |
| still_valid = mmget_still_valid(mm); |
| prev = NULL; |
| for (vma = mm->mmap; vma; vma = vma->vm_next) { |
| cond_resched(); |
| BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ |
| !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| if (vma->vm_userfaultfd_ctx.ctx != ctx) { |
| prev = vma; |
| continue; |
| } |
| new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| if (still_valid) { |
| prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, |
| new_flags, vma->anon_vma, |
| vma->vm_file, vma->vm_pgoff, |
| vma_policy(vma), |
| NULL_VM_UFFD_CTX); |
| if (prev) |
| vma = prev; |
| else |
| prev = vma; |
| } |
| vma->vm_flags = new_flags; |
| vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| } |
| up_write(&mm->mmap_sem); |
| mmput(mm); |
| wakeup: |
| /* |
| * After no new page faults can wait on this fault_*wqh, flush |
| * the last page faults that may have been already waiting on |
| * the fault_*wqh. |
| */ |
| spin_lock_irq(&ctx->fault_pending_wqh.lock); |
| __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
| __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); |
| spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
| |
| /* Flush pending events that may still wait on event_wqh */ |
| wake_up_all(&ctx->event_wqh); |
| |
| wake_up_poll(&ctx->fd_wqh, EPOLLHUP); |
| userfaultfd_ctx_put(ctx); |
| return 0; |
| } |
| |
| /* fault_pending_wqh.lock must be hold by the caller */ |
| static inline struct userfaultfd_wait_queue *find_userfault_in( |
| wait_queue_head_t *wqh) |
| { |
| wait_queue_entry_t *wq; |
| struct userfaultfd_wait_queue *uwq; |
| |
| lockdep_assert_held(&wqh->lock); |
| |
| uwq = NULL; |
| if (!waitqueue_active(wqh)) |
| goto out; |
| /* walk in reverse to provide FIFO behavior to read userfaults */ |
| wq = list_last_entry(&wqh->head, typeof(*wq), entry); |
| uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
| out: |
| return uwq; |
| } |
| |
| static inline struct userfaultfd_wait_queue *find_userfault( |
| struct userfaultfd_ctx *ctx) |
| { |
| return find_userfault_in(&ctx->fault_pending_wqh); |
| } |
| |
| static inline struct userfaultfd_wait_queue *find_userfault_evt( |
| struct userfaultfd_ctx *ctx) |
| { |
| return find_userfault_in(&ctx->event_wqh); |
| } |
| |
| static __poll_t userfaultfd_poll(struct file *file, poll_table *wait) |
| { |
| struct userfaultfd_ctx *ctx = file->private_data; |
| __poll_t ret; |
| |
| poll_wait(file, &ctx->fd_wqh, wait); |
| |
| switch (ctx->state) { |
| case UFFD_STATE_WAIT_API: |
| return EPOLLERR; |
| case UFFD_STATE_RUNNING: |
| /* |
| * poll() never guarantees that read won't block. |
| * userfaults can be waken before they're read(). |
| */ |
| if (unlikely(!(file->f_flags & O_NONBLOCK))) |
| return EPOLLERR; |
| /* |
| * lockless access to see if there are pending faults |
| * __pollwait last action is the add_wait_queue but |
| * the spin_unlock would allow the waitqueue_active to |
| * pass above the actual list_add inside |
| * add_wait_queue critical section. So use a full |
| * memory barrier to serialize the list_add write of |
| * add_wait_queue() with the waitqueue_active read |
| * below. |
| */ |
| ret = 0; |
| smp_mb(); |
| if (waitqueue_active(&ctx->fault_pending_wqh)) |
| ret = EPOLLIN; |
| else if (waitqueue_active(&ctx->event_wqh)) |
| ret = EPOLLIN; |
| |
| return ret; |
| default: |
| WARN_ON_ONCE(1); |
| return EPOLLERR; |
| } |
| } |
| |
| static const struct file_operations userfaultfd_fops; |
| |
| static int resolve_userfault_fork(struct userfaultfd_ctx *ctx, |
| struct userfaultfd_ctx *new, |
| struct uffd_msg *msg) |
| { |
| int fd; |
| |
| fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, new, |
| O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS)); |
| if (fd < 0) |
| return fd; |
| |
| msg->arg.reserved.reserved1 = 0; |
| msg->arg.fork.ufd = fd; |
| return 0; |
| } |
| |
| static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
| struct uffd_msg *msg) |
| { |
| ssize_t ret; |
| DECLARE_WAITQUEUE(wait, current); |
| struct userfaultfd_wait_queue *uwq; |
| /* |
| * Handling fork event requires sleeping operations, so |
| * we drop the event_wqh lock, then do these ops, then |
| * lock it back and wake up the waiter. While the lock is |
| * dropped the ewq may go away so we keep track of it |
| * carefully. |
| */ |
| LIST_HEAD(fork_event); |
| struct userfaultfd_ctx *fork_nctx = NULL; |
| |
| /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
| spin_lock_irq(&ctx->fd_wqh.lock); |
| __add_wait_queue(&ctx->fd_wqh, &wait); |
| for (;;) { |
| set_current_state(TASK_INTERRUPTIBLE); |
| spin_lock(&ctx->fault_pending_wqh.lock); |
| uwq = find_userfault(ctx); |
| if (uwq) { |
| /* |
| * Use a seqcount to repeat the lockless check |
| * in wake_userfault() to avoid missing |
| * wakeups because during the refile both |
| * waitqueue could become empty if this is the |
| * only userfault. |
| */ |
| write_seqcount_begin(&ctx->refile_seq); |
| |
| /* |
| * The fault_pending_wqh.lock prevents the uwq |
| * to disappear from under us. |
| * |
| * Refile this userfault from |
| * fault_pending_wqh to fault_wqh, it's not |
| * pending anymore after we read it. |
| * |
| * Use list_del() by hand (as |
| * userfaultfd_wake_function also uses |
| * list_del_init() by hand) to be sure nobody |
| * changes __remove_wait_queue() to use |
| * list_del_init() in turn breaking the |
| * !list_empty_careful() check in |
| * handle_userfault(). The uwq->wq.head list |
| * must never be empty at any time during the |
| * refile, or the waitqueue could disappear |
| * from under us. The "wait_queue_head_t" |
| * parameter of __remove_wait_queue() is unused |
| * anyway. |
| */ |
| list_del(&uwq->wq.entry); |
| add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
| |
| write_seqcount_end(&ctx->refile_seq); |
| |
| /* careful to always initialize msg if ret == 0 */ |
| *msg = uwq->msg; |
| spin_unlock(&ctx->fault_pending_wqh.lock); |
| ret = 0; |
| break; |
| } |
| spin_unlock(&ctx->fault_pending_wqh.lock); |
| |
| spin_lock(&ctx->event_wqh.lock); |
| uwq = find_userfault_evt(ctx); |
| if (uwq) { |
| *msg = uwq->msg; |
| |
| if (uwq->msg.event == UFFD_EVENT_FORK) { |
| fork_nctx = (struct userfaultfd_ctx *) |
| (unsigned long) |
| uwq->msg.arg.reserved.reserved1; |
| list_move(&uwq->wq.entry, &fork_event); |
| /* |
| * fork_nctx can be freed as soon as |
| * we drop the lock, unless we take a |
| * reference on it. |
| */ |
| userfaultfd_ctx_get(fork_nctx); |
| spin_unlock(&ctx->event_wqh.lock); |
| ret = 0; |
| break; |
| } |
| |
| userfaultfd_event_complete(ctx, uwq); |
| spin_unlock(&ctx->event_wqh.lock); |
| ret = 0; |
| break; |
| } |
| spin_unlock(&ctx->event_wqh.lock); |
| |
| if (signal_pending(current)) { |
| ret = -ERESTARTSYS; |
| break; |
| } |
| if (no_wait) { |
| ret = -EAGAIN; |
| break; |
| } |
| spin_unlock_irq(&ctx->fd_wqh.lock); |
| schedule(); |
| spin_lock_irq(&ctx->fd_wqh.lock); |
| } |
| __remove_wait_queue(&ctx->fd_wqh, &wait); |
| __set_current_state(TASK_RUNNING); |
| spin_unlock_irq(&ctx->fd_wqh.lock); |
| |
| if (!ret && msg->event == UFFD_EVENT_FORK) { |
| ret = resolve_userfault_fork(ctx, fork_nctx, msg); |
| spin_lock_irq(&ctx->event_wqh.lock); |
| if (!list_empty(&fork_event)) { |
| /* |
| * The fork thread didn't abort, so we can |
| * drop the temporary refcount. |
| */ |
| userfaultfd_ctx_put(fork_nctx); |
| |
| uwq = list_first_entry(&fork_event, |
| typeof(*uwq), |
| wq.entry); |
| /* |
| * If fork_event list wasn't empty and in turn |
| * the event wasn't already released by fork |
| * (the event is allocated on fork kernel |
| * stack), put the event back to its place in |
| * the event_wq. fork_event head will be freed |
| * as soon as we return so the event cannot |
| * stay queued there no matter the current |
| * "ret" value. |
| */ |
| list_del(&uwq->wq.entry); |
| __add_wait_queue(&ctx->event_wqh, &uwq->wq); |
| |
| /* |
| * Leave the event in the waitqueue and report |
| * error to userland if we failed to resolve |
| * the userfault fork. |
| */ |
| if (likely(!ret)) |
| userfaultfd_event_complete(ctx, uwq); |
| } else { |
| /* |
| * Here the fork thread aborted and the |
| * refcount from the fork thread on fork_nctx |
| * has already been released. We still hold |
| * the reference we took before releasing the |
| * lock above. If resolve_userfault_fork |
| * failed we've to drop it because the |
| * fork_nctx has to be freed in such case. If |
| * it succeeded we'll hold it because the new |
| * uffd references it. |
| */ |
| if (ret) |
| userfaultfd_ctx_put(fork_nctx); |
| } |
| spin_unlock_irq(&ctx->event_wqh.lock); |
| } |
| |
| return ret; |
| } |
| |
| static ssize_t userfaultfd_read(struct file *file, char __user *buf, |
| size_t count, loff_t *ppos) |
| { |
| struct userfaultfd_ctx *ctx = file->private_data; |
| ssize_t _ret, ret = 0; |
| struct uffd_msg msg; |
| int no_wait = file->f_flags & O_NONBLOCK; |
| |
| if (ctx->state == UFFD_STATE_WAIT_API) |
| return -EINVAL; |
| |
| for (;;) { |
| if (count < sizeof(msg)) |
| return ret ? ret : -EINVAL; |
| _ret = userfaultfd_ctx_read(ctx, no_wait, &msg); |
| if (_ret < 0) |
| return ret ? ret : _ret; |
| if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
| return ret ? ret : -EFAULT; |
| ret += sizeof(msg); |
| buf += sizeof(msg); |
| count -= sizeof(msg); |
| /* |
| * Allow to read more than one fault at time but only |
| * block if waiting for the very first one. |
| */ |
| no_wait = O_NONBLOCK; |
| } |
| } |
| |
| static void __wake_userfault(struct userfaultfd_ctx *ctx, |
| struct userfaultfd_wake_range *range) |
| { |
| spin_lock_irq(&ctx->fault_pending_wqh.lock); |
| /* wake all in the range and autoremove */ |
| if (waitqueue_active(&ctx->fault_pending_wqh)) |
| __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
| range); |
| if (waitqueue_active(&ctx->fault_wqh)) |
| __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); |
| spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
| } |
| |
| static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, |
| struct userfaultfd_wake_range *range) |
| { |
| unsigned seq; |
| bool need_wakeup; |
| |
| /* |
| * To be sure waitqueue_active() is not reordered by the CPU |
| * before the pagetable update, use an explicit SMP memory |
| * barrier here. PT lock release or up_read(mmap_sem) still |
| * have release semantics that can allow the |
| * waitqueue_active() to be reordered before the pte update. |
| */ |
| smp_mb(); |
| |
| /* |
| * Use waitqueue_active because it's very frequent to |
| * change the address space atomically even if there are no |
| * userfaults yet. So we take the spinlock only when we're |
| * sure we've userfaults to wake. |
| */ |
| do { |
| seq = read_seqcount_begin(&ctx->refile_seq); |
| need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || |
| waitqueue_active(&ctx->fault_wqh); |
| cond_resched(); |
| } while (read_seqcount_retry(&ctx->refile_seq, seq)); |
| if (need_wakeup) |
| __wake_userfault(ctx, range); |
| } |
| |
| static __always_inline int validate_range(struct mm_struct *mm, |
| __u64 *start, __u64 len) |
| { |
| __u64 task_size = mm->task_size; |
| |
| *start = untagged_addr(*start); |
| |
| if (*start & ~PAGE_MASK) |
| return -EINVAL; |
| if (len & ~PAGE_MASK) |
| return -EINVAL; |
| if (!len) |
| return -EINVAL; |
| if (*start < mmap_min_addr) |
| return -EINVAL; |
| if (*start >= task_size) |
| return -EINVAL; |
| if (len > task_size - *start) |
| return -EINVAL; |
| return 0; |
| } |
| |
| static inline bool vma_can_userfault(struct vm_area_struct *vma) |
| { |
| return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || |
| vma_is_shmem(vma); |
| } |
| |
| static int userfaultfd_register(struct userfaultfd_ctx *ctx, |
| unsigned long arg) |
| { |
| struct mm_struct *mm = ctx->mm; |
| struct vm_area_struct *vma, *prev, *cur; |
| int ret; |
| struct uffdio_register uffdio_register; |
| struct uffdio_register __user *user_uffdio_register; |
| unsigned long vm_flags, new_flags; |
| bool found; |
| bool basic_ioctls; |
| unsigned long start, end, vma_end; |
| |
| user_uffdio_register = (struct uffdio_register __user *) arg; |
| |
| ret = -EFAULT; |
| if (copy_from_user(&uffdio_register, user_uffdio_register, |
| sizeof(uffdio_register)-sizeof(__u64))) |
| goto out; |
| |
| ret = -EINVAL; |
| if (!uffdio_register.mode) |
| goto out; |
| if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING| |
| UFFDIO_REGISTER_MODE_WP)) |
| goto out; |
| vm_flags = 0; |
| if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) |
| vm_flags |= VM_UFFD_MISSING; |
| if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { |
| vm_flags |= VM_UFFD_WP; |
| /* |
| * FIXME: remove the below error constraint by |
| * implementing the wprotect tracking mode. |
| */ |
| ret = -EINVAL; |
| goto out; |
| } |
| |
| ret = validate_range(mm, &uffdio_register.range.start, |
| uffdio_register.range.len); |
| if (ret) |
| goto out; |
| |
| start = uffdio_register.range.start; |
| end = start + uffdio_register.range.len; |
| |
| ret = -ENOMEM; |
| if (!mmget_not_zero(mm)) |
| goto out; |
| |
| down_write(&mm->mmap_sem); |
| if (!mmget_still_valid(mm)) |
| goto out_unlock; |
| vma = find_vma_prev(mm, start, &prev); |
| if (!vma) |
| goto out_unlock; |
| |
| /* check that there's at least one vma in the range */ |
| ret = -EINVAL; |
| if (vma->vm_start >= end) |
| goto out_unlock; |
| |
| /* |
| * If the first vma contains huge pages, make sure start address |
| * is aligned to huge page size. |
| */ |
| if (is_vm_hugetlb_page(vma)) { |
| unsigned long vma_hpagesize = vma_kernel_pagesize(vma); |
| |
| if (start & (vma_hpagesize - 1)) |
| goto out_unlock; |
| } |
| |
| /* |
| * Search for not compatible vmas. |
| */ |
| found = false; |
| basic_ioctls = false; |
| for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| cond_resched(); |
| |
| BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| |
| /* check not compatible vmas */ |
| ret = -EINVAL; |
| if (!vma_can_userfault(cur)) |
| goto out_unlock; |
| |
| /* |
| * UFFDIO_COPY will fill file holes even without |
| * PROT_WRITE. This check enforces that if this is a |
| * MAP_SHARED, the process has write permission to the backing |
| * file. If VM_MAYWRITE is set it also enforces that on a |
| * MAP_SHARED vma: there is no F_WRITE_SEAL and no further |
| * F_WRITE_SEAL can be taken until the vma is destroyed. |
| */ |
| ret = -EPERM; |
| if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) |
| goto out_unlock; |
| |
| /* |
| * If this vma contains ending address, and huge pages |
| * check alignment. |
| */ |
| if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && |
| end > cur->vm_start) { |
| unsigned long vma_hpagesize = vma_kernel_pagesize(cur); |
| |
| ret = -EINVAL; |
| |
| if (end & (vma_hpagesize - 1)) |
| goto out_unlock; |
| } |
| |
| /* |
| * Check that this vma isn't already owned by a |
| * different userfaultfd. We can't allow more than one |
| * userfaultfd to own a single vma simultaneously or we |
| * wouldn't know which one to deliver the userfaults to. |
| */ |
| ret = -EBUSY; |
| if (cur->vm_userfaultfd_ctx.ctx && |
| cur->vm_userfaultfd_ctx.ctx != ctx) |
| goto out_unlock; |
| |
| /* |
| * Note vmas containing huge pages |
| */ |
| if (is_vm_hugetlb_page(cur)) |
| basic_ioctls = true; |
| |
| found = true; |
| } |
| BUG_ON(!found); |
| |
| if (vma->vm_start < start) |
| prev = vma; |
| |
| ret = 0; |
| do { |
| cond_resched(); |
| |
| BUG_ON(!vma_can_userfault(vma)); |
| BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
| vma->vm_userfaultfd_ctx.ctx != ctx); |
| WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
| |
| /* |
| * Nothing to do: this vma is already registered into this |
| * userfaultfd and with the right tracking mode too. |
| */ |
| if (vma->vm_userfaultfd_ctx.ctx == ctx && |
| (vma->vm_flags & vm_flags) == vm_flags) |
| goto skip; |
| |
| if (vma->vm_start > start) |
| start = vma->vm_start; |
| vma_end = min(end, vma->vm_end); |
| |
| new_flags = (vma->vm_flags & ~vm_flags) | vm_flags; |
| prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| vma_policy(vma), |
| ((struct vm_userfaultfd_ctx){ ctx })); |
| if (prev) { |
| vma = prev; |
| goto next; |
| } |
| if (vma->vm_start < start) { |
| ret = split_vma(mm, vma, start, 1); |
| if (ret) |
| break; |
| } |
| if (vma->vm_end > end) { |
| ret = split_vma(mm, vma, end, 0); |
| if (ret) |
| break; |
| } |
| next: |
| /* |
| * In the vma_merge() successful mprotect-like case 8: |
| * the next vma was merged into the current one and |
| * the current one has not been updated yet. |
| */ |
| vma->vm_flags = new_flags; |
| vma->vm_userfaultfd_ctx.ctx = ctx; |
| |
| skip: |
| prev = vma; |
| start = vma->vm_end; |
| vma = vma->vm_next; |
| } while (vma && vma->vm_start < end); |
| out_unlock: |
| up_write(&mm->mmap_sem); |
| mmput(mm); |
| if (!ret) { |
| /* |
| * Now that we scanned all vmas we can already tell |
| * userland which ioctls methods are guaranteed to |
| * succeed on this range. |
| */ |
| if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : |
| UFFD_API_RANGE_IOCTLS, |
| &user_uffdio_register->ioctls)) |
| ret = -EFAULT; |
| } |
| out: |
| return ret; |
| } |
| |
| static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, |
| unsigned long arg) |
| { |
| struct mm_struct *mm = ctx->mm; |
| struct vm_area_struct *vma, *prev, *cur; |
| int ret; |
| struct uffdio_range uffdio_unregister; |
| unsigned long new_flags; |
| bool found; |
| unsigned long start, end, vma_end; |
| const void __user *buf = (void __user *)arg; |
| |
| ret = -EFAULT; |
| if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) |
| goto out; |
| |
| ret = validate_range(mm, &uffdio_unregister.start, |
| uffdio_unregister.len); |
| if (ret) |
| goto out; |
| |
| start = uffdio_unregister.start; |
| end = start + uffdio_unregister.len; |
| |
| ret = -ENOMEM; |
| if (!mmget_not_zero(mm)) |
| goto out; |
| |
| down_write(&mm->mmap_sem); |
| if (!mmget_still_valid(mm)) |
| goto out_unlock; |
| vma = find_vma_prev(mm, start, &prev); |
| if (!vma) |
| goto out_unlock; |
| |
| /* check that there's at least one vma in the range */ |
| ret = -EINVAL; |
| if (vma->vm_start >= end) |
| goto out_unlock; |
| |
| /* |
| * If the first vma contains huge pages, make sure start address |
| * is aligned to huge page size. |
| */ |
| if (is_vm_hugetlb_page(vma)) { |
| unsigned long vma_hpagesize = vma_kernel_pagesize(vma); |
| |
| if (start & (vma_hpagesize - 1)) |
| goto out_unlock; |
| } |
| |
| /* |
| * Search for not compatible vmas. |
| */ |
| found = false; |
| ret = -EINVAL; |
| for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
| cond_resched(); |
| |
| BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ |
| !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); |
| |
| /* |
| * Check not compatible vmas, not strictly required |
| * here as not compatible vmas cannot have an |
| * userfaultfd_ctx registered on them, but this |
| * provides for more strict behavior to notice |
| * unregistration errors. |
| */ |
| if (!vma_can_userfault(cur)) |
| goto out_unlock; |
| |
| found = true; |
| } |
| BUG_ON(!found); |
| |
| if (vma->vm_start < start) |
| prev = vma; |
| |
| ret = 0; |
| do { |
| cond_resched(); |
| |
| BUG_ON(!vma_can_userfault(vma)); |
| |
| /* |
| * Nothing to do: this vma is already registered into this |
| * userfaultfd and with the right tracking mode too. |
| */ |
| if (!vma->vm_userfaultfd_ctx.ctx) |
| goto skip; |
| |
| WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
| |
| if (vma->vm_start > start) |
| start = vma->vm_start; |
| vma_end = min(end, vma->vm_end); |
| |
| if (userfaultfd_missing(vma)) { |
| /* |
| * Wake any concurrent pending userfault while |
| * we unregister, so they will not hang |
| * permanently and it avoids userland to call |
| * UFFDIO_WAKE explicitly. |
| */ |
| struct userfaultfd_wake_range range; |
| range.start = start; |
| range.len = vma_end - start; |
| wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); |
| } |
| |
| new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
| prev = vma_merge(mm, prev, start, vma_end, new_flags, |
| vma->anon_vma, vma->vm_file, vma->vm_pgoff, |
| vma_policy(vma), |
| NULL_VM_UFFD_CTX); |
| if (prev) { |
| vma = prev; |
| goto next; |
| } |
| if (vma->vm_start < start) { |
| ret = split_vma(mm, vma, start, 1); |
| if (ret) |
| break; |
| } |
| if (vma->vm_end > end) { |
| ret = split_vma(mm, vma, end, 0); |
| if (ret) |
| break; |
| } |
| next: |
| /* |
| * In the vma_merge() successful mprotect-like case 8: |
| * the next vma was merged into the current one and |
| * the current one has not been updated yet. |
| */ |
| vma->vm_flags = new_flags; |
| vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
| |
| skip: |
| prev = vma; |
| start = vma->vm_end; |
| vma = vma->vm_next; |
| } while (vma && vma->vm_start < end); |
| out_unlock: |
| up_write(&mm->mmap_sem); |
| mmput(mm); |
| out: |
| return ret; |
| } |
| |
| /* |
| * userfaultfd_wake may be used in combination with the |
| * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. |
| */ |
| static int userfaultfd_wake(struct userfaultfd_ctx *ctx, |
| unsigned long arg) |
| { |
| int ret; |
| struct uffdio_range uffdio_wake; |
| struct userfaultfd_wake_range range; |
| const void __user *buf = (void __user *)arg; |
| |
| ret = -EFAULT; |
| if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) |
| goto out; |
| |
| ret = validate_range(ctx->mm, &uffdio_wake.start, uffdio_wake.len); |
| if (ret) |
| goto out; |
| |
| range.start = uffdio_wake.start; |
| range.len = uffdio_wake.len; |
| |
| /* |
| * len == 0 means wake all and we don't want to wake all here, |
| * so check it again to be sure. |
| */ |
| VM_BUG_ON(!range.len); |
| |
| wake_userfault(ctx, &range); |
| ret = 0; |
| |
| out: |
| return ret; |
| } |
| |
| static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
| unsigned long arg) |
| { |
| __s64 ret; |
| struct uffdio_copy uffdio_copy; |
| struct uffdio_copy __user *user_uffdio_copy; |
| struct userfaultfd_wake_range range; |
| |
| user_uffdio_copy = (struct uffdio_copy __user *) arg; |
| |
| ret = -EAGAIN; |
| if (READ_ONCE(ctx->mmap_changing)) |
| goto out; |
| |
| ret = -EFAULT; |
| if (copy_from_user(&uffdio_copy, user_uffdio_copy, |
| /* don't copy "copy" last field */ |
| sizeof(uffdio_copy)-sizeof(__s64))) |
| goto out; |
| |
| ret = validate_range(ctx->mm, &uffdio_copy.dst, uffdio_copy.len); |
| if (ret) |
| goto out; |
| /* |
| * double check for wraparound just in case. copy_from_user() |
| * will later check uffdio_copy.src + uffdio_copy.len to fit |
| * in the userland range. |
| */ |
| ret = -EINVAL; |
| if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) |
| goto out; |
| if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) |
| goto out; |
| if (mmget_not_zero(ctx->mm)) { |
| ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, |
| uffdio_copy.len, &ctx->mmap_changing); |
| mmput(ctx->mm); |
| } else { |
| return -ESRCH; |
| } |
| if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
| return -EFAULT; |
| if (ret < 0) |
| goto out; |
| BUG_ON(!ret); |
| /* len == 0 would wake all */ |
| range.len = ret; |
| if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { |
| range.start = uffdio_copy.dst; |
| wake_userfault(ctx, &range); |
| } |
| ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; |
| out: |
| return ret; |
| } |
| |
| static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, |
| unsigned long arg) |
| { |
| __s64 ret; |
| struct uffdio_zeropage uffdio_zeropage; |
| struct uffdio_zeropage __user *user_uffdio_zeropage; |
| struct userfaultfd_wake_range range; |
| |
| user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; |
| |
| ret = -EAGAIN; |
| if (READ_ONCE(ctx->mmap_changing)) |
| goto out; |
| |
| ret = -EFAULT; |
| if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, |
| /* don't copy "zeropage" last field */ |
| sizeof(uffdio_zeropage)-sizeof(__s64))) |
| goto out; |
| |
| ret = validate_range(ctx->mm, &uffdio_zeropage.range.start, |
| uffdio_zeropage.range.len); |
| if (ret) |
| goto out; |
| ret = -EINVAL; |
| if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) |
| goto out; |
| |
| if (mmget_not_zero(ctx->mm)) { |
| ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, |
| uffdio_zeropage.range.len, |
| &ctx->mmap_changing); |
| mmput(ctx->mm); |
| } else { |
| return -ESRCH; |
| } |
| if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
| return -EFAULT; |
| if (ret < 0) |
| goto out; |
| /* len == 0 would wake all */ |
| BUG_ON(!ret); |
| range.len = ret; |
| if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { |
| range.start = uffdio_zeropage.range.start; |
| wake_userfault(ctx, &range); |
| } |
| ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; |
| out: |
| return ret; |
| } |
| |
| static inline unsigned int uffd_ctx_features(__u64 user_features) |
| { |
| /* |
| * For the current set of features the bits just coincide |
| */ |
| return (unsigned int)user_features; |
| } |
| |
| /* |
| * userland asks for a certain API version and we return which bits |
| * and ioctl commands are implemented in this kernel for such API |
| * version or -EINVAL if unknown. |
| */ |
| static int userfaultfd_api(struct userfaultfd_ctx *ctx, |
| unsigned long arg) |
| { |
| struct uffdio_api uffdio_api; |
| void __user *buf = (void __user *)arg; |
| int ret; |
| __u64 features; |
| |
| ret = -EINVAL; |
| if (ctx->state != UFFD_STATE_WAIT_API) |
| goto out; |
| ret = -EFAULT; |
| if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
| goto out; |
| features = uffdio_api.features; |
| if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) { |
| memset(&uffdio_api, 0, sizeof(uffdio_api)); |
| if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| goto out; |
| ret = -EINVAL; |
| goto out; |
| } |
| /* report all available features and ioctls to userland */ |
| uffdio_api.features = UFFD_API_FEATURES; |
| uffdio_api.ioctls = UFFD_API_IOCTLS; |
| ret = -EFAULT; |
| if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) |
| goto out; |
| ctx->state = UFFD_STATE_RUNNING; |
| /* only enable the requested features for this uffd context */ |
| ctx->features = uffd_ctx_features(features); |
| ret = 0; |
| out: |
| return ret; |
| } |
| |
| static long userfaultfd_ioctl(struct file *file, unsigned cmd, |
| unsigned long arg) |
| { |
| int ret = -EINVAL; |
| struct userfaultfd_ctx *ctx = file->private_data; |
| |
| if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API) |
| return -EINVAL; |
| |
| switch(cmd) { |
| case UFFDIO_API: |
| ret = userfaultfd_api(ctx, arg); |
| break; |
| case UFFDIO_REGISTER: |
| ret = userfaultfd_register(ctx, arg); |
| break; |
| case UFFDIO_UNREGISTER: |
| ret = userfaultfd_unregister(ctx, arg); |
| break; |
| case UFFDIO_WAKE: |
| ret = userfaultfd_wake(ctx, arg); |
| break; |
| case UFFDIO_COPY: |
| ret = userfaultfd_copy(ctx, arg); |
| break; |
| case UFFDIO_ZEROPAGE: |
| ret = userfaultfd_zeropage(ctx, arg); |
| break; |
| } |
| return ret; |
| } |
| |
| #ifdef CONFIG_PROC_FS |
| static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) |
| { |
| struct userfaultfd_ctx *ctx = f->private_data; |
| wait_queue_entry_t *wq; |
| unsigned long pending = 0, total = 0; |
| |
| spin_lock_irq(&ctx->fault_pending_wqh.lock); |
| list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { |
| pending++; |
| total++; |
| } |
| list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { |
| total++; |
| } |
| spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
| |
| /* |
| * If more protocols will be added, there will be all shown |
| * separated by a space. Like this: |
| * protocols: aa:... bb:... |
| */ |
| seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", |
| pending, total, UFFD_API, ctx->features, |
| UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
| } |
| #endif |
| |
| static const struct file_operations userfaultfd_fops = { |
| #ifdef CONFIG_PROC_FS |
| .show_fdinfo = userfaultfd_show_fdinfo, |
| #endif |
| .release = userfaultfd_release, |
| .poll = userfaultfd_poll, |
| .read = userfaultfd_read, |
| .unlocked_ioctl = userfaultfd_ioctl, |
| .compat_ioctl = userfaultfd_ioctl, |
| .llseek = noop_llseek, |
| }; |
| |
| static void init_once_userfaultfd_ctx(void *mem) |
| { |
| struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; |
| |
| init_waitqueue_head(&ctx->fault_pending_wqh); |
| init_waitqueue_head(&ctx->fault_wqh); |
| init_waitqueue_head(&ctx->event_wqh); |
| init_waitqueue_head(&ctx->fd_wqh); |
| seqcount_init(&ctx->refile_seq); |
| } |
| |
| SYSCALL_DEFINE1(userfaultfd, int, flags) |
| { |
| struct userfaultfd_ctx *ctx; |
| int fd; |
| |
| if (!sysctl_unprivileged_userfaultfd && !capable(CAP_SYS_PTRACE)) |
| return -EPERM; |
| |
| BUG_ON(!current->mm); |
| |
| /* Check the UFFD_* constants for consistency. */ |
| BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); |
| BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); |
| |
| if (flags & ~UFFD_SHARED_FCNTL_FLAGS) |
| return -EINVAL; |
| |
| ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
| if (!ctx) |
| return -ENOMEM; |
| |
| refcount_set(&ctx->refcount, 1); |
| ctx->flags = flags; |
| ctx->features = 0; |
| ctx->state = UFFD_STATE_WAIT_API; |
| ctx->released = false; |
| ctx->mmap_changing = false; |
| ctx->mm = current->mm; |
| /* prevent the mm struct to be freed */ |
| mmgrab(ctx->mm); |
| |
| fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx, |
| O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS)); |
| if (fd < 0) { |
| mmdrop(ctx->mm); |
| kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
| } |
| return fd; |
| } |
| |
| static int __init userfaultfd_init(void) |
| { |
| userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", |
| sizeof(struct userfaultfd_ctx), |
| 0, |
| SLAB_HWCACHE_ALIGN|SLAB_PANIC, |
| init_once_userfaultfd_ctx); |
| return 0; |
| } |
| __initcall(userfaultfd_init); |