* [PATCH v2 2/3] userfaultfd: merge fs/userfaultfd.c into mm/userfaultfd.c
2026-05-01 14:54 [PATCH v2 0/3] userfaultfd: merge fs/userfaultfd.c into mm/userfaultfd.c Mike Rapoport
2026-05-01 14:54 ` [PATCH v2 1/3] userfaultfd: ensure mremap_userfaultfd_fail() releases mmap_changing Mike Rapoport
@ 2026-05-01 14:54 ` Mike Rapoport
2026-05-01 14:54 ` [PATCH v2 3/3] userfaultfd: make functions that are not used outside uffd static Mike Rapoport
2 siblings, 0 replies; 4+ messages in thread
From: Mike Rapoport @ 2026-05-01 14:54 UTC (permalink / raw)
To: Andrew Morton
Cc: Alexander Viro, Christian Brauner, David Hildenbrand, Jan Kara,
Mike Rapoport, Peter Xu, linux-fsdevel, linux-kernel, linux-mm
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Historically userfaultfd implementation has been split between
fs/userfaultfd.c and mm/userfaultfd.c.
The mm/ part implemented memory management operations, while the fs/ part
implemented file descriptor handling and called into the mm/ part for the
actual memory management work.
This separation is quite artificial and fs/userfaultfd.c does not seem to
belong to fs/ because it's only a user if vfs APIs and like for other
users, for example, memfd and secretmem, the file descriptor handling could
live in mm/ as well.
"Append" fs/userfaultfd.c to mm/userfaultfd and update fs/Makefile and
MAINTAINERS accordingly.
No intended functional changes.
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Assisted-by: Copilot:claude-opus-4-6
---
MAINTAINERS | 1 -
fs/Makefile | 1 -
fs/userfaultfd.c | 2232 ----------------------------------------------
mm/userfaultfd.c | 2215 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 2215 insertions(+), 2234 deletions(-)
delete mode 100644 fs/userfaultfd.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 2fb1c75afd16..afd3343a7336 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17071,7 +17071,6 @@ R: Peter Xu <peterx@redhat.com>
L: linux-mm@kvack.org
S: Maintained
F: Documentation/admin-guide/mm/userfaultfd.rst
-F: fs/userfaultfd.c
F: include/asm-generic/pgtable_uffd.h
F: include/linux/userfaultfd_k.h
F: include/uapi/linux/userfaultfd.h
diff --git a/fs/Makefile b/fs/Makefile
index ae1b07f9c6a0..89a8a9d207d1 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -27,7 +27,6 @@ obj-y += anon_inodes.o
obj-$(CONFIG_SIGNALFD) += signalfd.o
obj-$(CONFIG_TIMERFD) += timerfd.o
obj-$(CONFIG_EVENTFD) += eventfd.o
-obj-$(CONFIG_USERFAULTFD) += userfaultfd.o
obj-$(CONFIG_AIO) += aio.o
obj-$(CONFIG_FS_DAX) += dax.o
obj-$(CONFIG_FS_ENCRYPTION) += crypto/
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
deleted file mode 100644
index ef963a58f1a1..000000000000
--- a/fs/userfaultfd.c
+++ /dev/null
@@ -1,2232 +0,0 @@
-// 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/mm_inline.h>
-#include <linux/mmu_notifier.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>
-#include <linux/leafops.h>
-#include <linux/miscdevice.h>
-#include <linux/uio.h>
-
-static int sysctl_unprivileged_userfaultfd __read_mostly;
-
-#ifdef CONFIG_SYSCTL
-static const struct ctl_table vm_userfaultfd_table[] = {
- {
- .procname = "unprivileged_userfaultfd",
- .data = &sysctl_unprivileged_userfaultfd,
- .maxlen = sizeof(sysctl_unprivileged_userfaultfd),
- .mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_ONE,
- },
-};
-#endif
-
-static struct kmem_cache *userfaultfd_ctx_cachep __ro_after_init;
-
-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;
-};
-
-/* internal indication that UFFD_API ioctl was successfully executed */
-#define UFFD_FEATURE_INITIALIZED (1u << 31)
-
-static bool userfaultfd_is_initialized(struct userfaultfd_ctx *ctx)
-{
- return ctx->features & UFFD_FEATURE_INITIALIZED;
-}
-
-static bool userfaultfd_wp_async_ctx(struct userfaultfd_ctx *ctx)
-{
- return ctx && (ctx->features & UFFD_FEATURE_WP_ASYNC);
-}
-
-/*
- * Whether WP_UNPOPULATED is enabled on the uffd context. It is only
- * meaningful when userfaultfd_wp()==true on the vma and when it's
- * anonymous.
- */
-bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma)
-{
- struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
-
- if (!ctx)
- return false;
-
- return ctx->features & UFFD_FEATURE_WP_UNPOPULATED;
-}
-
-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_WARN_ON_ONCE(spin_is_locked(&ctx->fault_pending_wqh.lock));
- VM_WARN_ON_ONCE(waitqueue_active(&ctx->fault_pending_wqh));
- VM_WARN_ON_ONCE(spin_is_locked(&ctx->fault_wqh.lock));
- VM_WARN_ON_ONCE(waitqueue_active(&ctx->fault_wqh));
- VM_WARN_ON_ONCE(spin_is_locked(&ctx->event_wqh.lock));
- VM_WARN_ON_ONCE(waitqueue_active(&ctx->event_wqh));
- VM_WARN_ON_ONCE(spin_is_locked(&ctx->fd_wqh.lock));
- VM_WARN_ON_ONCE(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 long real_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 = (features & UFFD_FEATURE_EXACT_ADDRESS) ?
- real_address : address;
-
- /*
- * These flags indicate why the userfault occurred:
- * - UFFD_PAGEFAULT_FLAG_WP indicates a write protect fault.
- * - UFFD_PAGEFAULT_FLAG_MINOR indicates a minor fault.
- * - Neither of these flags being set indicates a MISSING fault.
- *
- * Separately, UFFD_PAGEFAULT_FLAG_WRITE indicates it was a write
- * fault. Otherwise, it was a read fault.
- */
- if (flags & FAULT_FLAG_WRITE)
- msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
- if (reason & VM_UFFD_WP)
- msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
- if (reason & VM_UFFD_MINOR)
- msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_MINOR;
- 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_fault *vmf,
- unsigned long reason)
-{
- struct vm_area_struct *vma = vmf->vma;
- pte_t *ptep, pte;
-
- assert_fault_locked(vmf);
-
- ptep = hugetlb_walk(vma, vmf->address, vma_mmu_pagesize(vma));
- if (!ptep)
- return true;
-
- pte = huge_ptep_get(vma->vm_mm, vmf->address, ptep);
-
- /*
- * Lockless access: we're in a wait_event so it's ok if it
- * changes under us.
- */
-
- /* Entry is still missing, wait for userspace to resolve the fault. */
- if (huge_pte_none(pte))
- return true;
- /* UFFD PTE markers require userspace to resolve the fault. */
- if (pte_is_uffd_marker(pte))
- return true;
- /*
- * If VMA has UFFD WP faults enabled and WP fault, wait for userspace to
- * resolve the fault.
- */
- if (!huge_pte_write(pte) && (reason & VM_UFFD_WP))
- return true;
-
- return false;
-}
-#else
-static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
- struct vm_fault *vmf,
- unsigned long reason)
-{
- /* Should never get here. */
- VM_WARN_ON_ONCE(1);
- return false;
-}
-#endif /* CONFIG_HUGETLB_PAGE */
-
-/*
- * Verify the pagetables are still not ok after having registered into
- * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any
- * userfault that has already been resolved, if userfaultfd_read_iter and
- * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different
- * threads.
- */
-static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
- struct vm_fault *vmf,
- unsigned long reason)
-{
- struct mm_struct *mm = ctx->mm;
- unsigned long address = vmf->address;
- pgd_t *pgd;
- p4d_t *p4d;
- pud_t *pud;
- pmd_t *pmd, _pmd;
- pte_t *pte;
- pte_t ptent;
- bool ret;
-
- assert_fault_locked(vmf);
-
- pgd = pgd_offset(mm, address);
- if (!pgd_present(*pgd))
- return true;
- p4d = p4d_offset(pgd, address);
- if (!p4d_present(*p4d))
- return true;
- pud = pud_offset(p4d, address);
- if (!pud_present(*pud))
- return true;
- pmd = pmd_offset(pud, address);
-again:
- _pmd = pmdp_get_lockless(pmd);
- if (pmd_none(_pmd))
- return true;
-
- /*
- * A race could arise which would result in a softleaf entry such as
- * migration entry unexpectedly being present in the PMD, so explicitly
- * check for this and bail out if so.
- */
- if (!pmd_present(_pmd))
- return false;
-
- if (pmd_trans_huge(_pmd))
- return !pmd_write(_pmd) && (reason & VM_UFFD_WP);
-
- pte = pte_offset_map(pmd, address);
- if (!pte)
- goto again;
-
- /*
- * Lockless access: we're in a wait_event so it's ok if it
- * changes under us.
- */
- ptent = ptep_get(pte);
-
- ret = true;
- /* Entry is still missing, wait for userspace to resolve the fault. */
- if (pte_none(ptent))
- goto out;
- /* UFFD PTE markers require userspace to resolve the fault. */
- if (pte_is_uffd_marker(ptent))
- goto out;
- /*
- * If VMA has UFFD WP faults enabled and WP fault, wait for userspace to
- * resolve the fault.
- */
- if (!pte_write(ptent) && (reason & VM_UFFD_WP))
- goto out;
-
- ret = false;
-out:
- pte_unmap(pte);
- return ret;
-}
-
-static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags)
-{
- if (flags & FAULT_FLAG_INTERRUPTIBLE)
- return TASK_INTERRUPTIBLE;
-
- if (flags & FAULT_FLAG_KILLABLE)
- return TASK_KILLABLE;
-
- return TASK_UNINTERRUPTIBLE;
-}
-
-/*
- * 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_lock 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_lock must be released before
- * returning it.
- */
-vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
-{
- struct vm_area_struct *vma = vmf->vma;
- struct mm_struct *mm = vma->vm_mm;
- struct userfaultfd_ctx *ctx;
- struct userfaultfd_wait_queue uwq;
- vm_fault_t ret = VM_FAULT_SIGBUS;
- bool must_wait;
- unsigned int blocking_state;
-
- /*
- * We don't do userfault handling for the final child pid update
- * and when coredumping (faults triggered by get_dump_page()).
- */
- if (current->flags & (PF_EXITING|PF_DUMPCORE))
- goto out;
-
- assert_fault_locked(vmf);
-
- ctx = vma->vm_userfaultfd_ctx.ctx;
- if (!ctx)
- goto out;
-
- VM_WARN_ON_ONCE(ctx->mm != mm);
-
- /* Any unrecognized flag is a bug. */
- VM_WARN_ON_ONCE(reason & ~__VM_UFFD_FLAGS);
- /* 0 or > 1 flags set is a bug; we expect exactly 1. */
- VM_WARN_ON_ONCE(!reason || (reason & (reason - 1)));
-
- if (ctx->features & UFFD_FEATURE_SIGBUS)
- goto out;
- if (!(vmf->flags & FAULT_FLAG_USER) && (ctx->flags & UFFD_USER_MODE_ONLY))
- 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.
- */
- VM_WARN_ON_ONCE(vmf->flags & FAULT_FLAG_RETRY_NOWAIT);
-#ifdef CONFIG_DEBUG_VM
- if (printk_ratelimit()) {
- pr_warn("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;
-
- if (unlikely(READ_ONCE(ctx->released))) {
- /*
- * If a concurrent release is detected, do not return
- * VM_FAULT_SIGBUS or VM_FAULT_NOPAGE, but instead always
- * return VM_FAULT_RETRY with lock released proactively.
- *
- * 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, to avoid involuntary SIGBUS triggered.
- *
- * If we were to return VM_FAULT_NOPAGE, it would work for
- * the fault path, in which the lock will be released
- * later. However for GUP, faultin_page() does nothing
- * special on NOPAGE, so GUP would spin retrying without
- * releasing the mmap read lock, causing possible livelock.
- *
- * Here only VM_FAULT_RETRY would make sure the mmap lock
- * be released immediately, so that the thread concurrently
- * releasing the userfault would always make progress.
- */
- release_fault_lock(vmf);
- goto out;
- }
-
- /* take the reference before dropping the mmap_lock */
- userfaultfd_ctx_get(ctx);
-
- init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
- uwq.wq.private = current;
- uwq.msg = userfault_msg(vmf->address, vmf->real_address, vmf->flags,
- reason, ctx->features);
- uwq.ctx = ctx;
- uwq.waken = false;
-
- blocking_state = userfaultfd_get_blocking_state(vmf->flags);
-
- /*
- * Take the vma lock now, in order to safely call
- * userfaultfd_huge_must_wait() later. Since acquiring the
- * (sleepable) vma lock can modify the current task state, that
- * must be before explicitly calling set_current_state().
- */
- if (is_vm_hugetlb_page(vma))
- hugetlb_vma_lock_read(vma);
-
- 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(vma)) {
- must_wait = userfaultfd_huge_must_wait(ctx, vmf, reason);
- hugetlb_vma_unlock_read(vma);
- } else {
- must_wait = userfaultfd_must_wait(ctx, vmf, reason);
- }
-
- release_fault_lock(vmf);
-
- if (likely(must_wait && !READ_ONCE(ctx->released))) {
- wake_up_poll(&ctx->fd_wqh, EPOLLIN);
- schedule();
- }
-
- __set_current_state(TASK_RUNNING);
-
- /*
- * 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) {
- userfaultfd_release_new(release_new_ctx);
- userfaultfd_ctx_put(release_new_ctx);
- }
-
- /*
- * ctx may go away after this if the userfault pseudo fd is
- * already released.
- */
-out:
- atomic_dec(&ctx->mmap_changing);
- VM_WARN_ON_ONCE(atomic_read(&ctx->mmap_changing) < 0);
- 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)
- return 0;
-
- if (!(octx->features & UFFD_FEATURE_EVENT_FORK)) {
- userfaultfd_reset_ctx(vma);
- return 0;
- }
-
- list_for_each_entry(fctx, fcs, list)
- if (fctx->orig == octx) {
- ctx = fctx->new;
- break;
- }
-
- if (!ctx) {
- fctx = kmalloc_obj(*fctx);
- 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->features = octx->features;
- ctx->released = false;
- init_rwsem(&ctx->map_changing_lock);
- atomic_set(&ctx->mmap_changing, 0);
- ctx->mm = vma->vm_mm;
- mmgrab(ctx->mm);
-
- userfaultfd_ctx_get(octx);
- down_write(&octx->map_changing_lock);
- atomic_inc(&octx->mmap_changing);
- up_write(&octx->map_changing_lock);
- 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 dup_userfaultfd_fail(struct list_head *fcs)
-{
- struct userfaultfd_fork_ctx *fctx, *n;
-
- /*
- * An error has occurred on fork, we will tear memory down, but have
- * allocated memory for fctx's and raised reference counts for both the
- * original and child contexts (and on the mm for each as a result).
- *
- * These would ordinarily be taken care of by a user handling the event,
- * but we are no longer doing so, so manually clean up here.
- *
- * mm tear down will take care of cleaning up VMA contexts.
- */
- list_for_each_entry_safe(fctx, n, fcs, list) {
- struct userfaultfd_ctx *octx = fctx->orig;
- struct userfaultfd_ctx *ctx = fctx->new;
-
- atomic_dec(&octx->mmap_changing);
- VM_WARN_ON_ONCE(atomic_read(&octx->mmap_changing) < 0);
- userfaultfd_ctx_put(octx);
- userfaultfd_ctx_put(ctx);
-
- 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);
- down_write(&ctx->map_changing_lock);
- atomic_inc(&ctx->mmap_changing);
- up_write(&ctx->map_changing_lock);
- } else {
- /* Drop uffd context if remap feature not enabled */
- userfaultfd_reset_ctx(vma);
- }
-}
-
-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;
-
- 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);
-}
-
-void mremap_userfaultfd_fail(struct vm_userfaultfd_ctx *vm_ctx)
-{
- struct userfaultfd_ctx *ctx = vm_ctx->ctx;
-
- if (!ctx)
- return;
-
- atomic_dec(&ctx->mmap_changing);
- userfaultfd_ctx_put(ctx);
-}
-
-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);
- down_write(&ctx->map_changing_lock);
- atomic_inc(&ctx->mmap_changing);
- up_write(&ctx->map_changing_lock);
- mmap_read_unlock(mm);
-
- 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)
-{
- 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))
- return 0;
-
- unmap_ctx = kzalloc_obj(*unmap_ctx);
- if (!unmap_ctx)
- return -ENOMEM;
-
- userfaultfd_ctx_get(ctx);
- down_write(&ctx->map_changing_lock);
- atomic_inc(&ctx->mmap_changing);
- up_write(&ctx->map_changing_lock);
- 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;
- /* len == 0 means wake all */
- struct userfaultfd_wake_range range = { .len = 0, };
-
- WRITE_ONCE(ctx->released, true);
-
- userfaultfd_release_all(mm, ctx);
-
- /*
- * 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);
-
- if (!userfaultfd_is_initialized(ctx))
- return EPOLLERR;
-
- /*
- * 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;
-}
-
-static const struct file_operations userfaultfd_fops;
-
-static int resolve_userfault_fork(struct userfaultfd_ctx *new,
- struct inode *inode,
- struct uffd_msg *msg)
-{
- int fd;
-
- fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, new,
- O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode);
- 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, struct inode *inode)
-{
- 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(fork_nctx, inode, 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_iter(struct kiocb *iocb, struct iov_iter *to)
-{
- struct file *file = iocb->ki_filp;
- struct userfaultfd_ctx *ctx = file->private_data;
- ssize_t _ret, ret = 0;
- struct uffd_msg msg;
- struct inode *inode = file_inode(file);
- bool no_wait;
-
- if (!userfaultfd_is_initialized(ctx))
- return -EINVAL;
-
- no_wait = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT;
- for (;;) {
- if (iov_iter_count(to) < sizeof(msg))
- return ret ? ret : -EINVAL;
- _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode);
- if (_ret < 0)
- return ret ? ret : _ret;
- _ret = !copy_to_iter_full(&msg, sizeof(msg), to);
- if (_ret)
- return ret ? ret : -EFAULT;
- ret += sizeof(msg);
- /*
- * Allow to read more than one fault at time but only
- * block if waiting for the very first one.
- */
- no_wait = true;
- }
-}
-
-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 mmap_read_unlock(mm) 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_unaligned_range(
- struct mm_struct *mm, __u64 start, __u64 len)
-{
- __u64 task_size = mm->task_size;
-
- if (len & ~PAGE_MASK)
- return -EINVAL;
- if (!len)
- return -EINVAL;
- if (start >= task_size)
- return -EINVAL;
- if (len > task_size - start)
- return -EINVAL;
- if (start + len <= start)
- return -EINVAL;
- return 0;
-}
-
-static __always_inline int validate_range(struct mm_struct *mm,
- __u64 start, __u64 len)
-{
- if (start & ~PAGE_MASK)
- return -EINVAL;
-
- return validate_unaligned_range(mm, start, len);
-}
-
-static int userfaultfd_register(struct userfaultfd_ctx *ctx,
- unsigned long arg)
-{
- struct mm_struct *mm = ctx->mm;
- struct vm_area_struct *vma, *cur;
- int ret;
- struct uffdio_register uffdio_register;
- struct uffdio_register __user *user_uffdio_register;
- vm_flags_t vm_flags;
- bool found;
- bool basic_ioctls;
- unsigned long start, end;
- struct vma_iterator vmi;
- bool wp_async = userfaultfd_wp_async_ctx(ctx);
-
- 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 & ~UFFD_API_REGISTER_MODES)
- 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) {
- if (!pgtable_supports_uffd_wp())
- goto out;
-
- vm_flags |= VM_UFFD_WP;
- }
- if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
- goto out;
-#endif
- vm_flags |= VM_UFFD_MINOR;
- }
-
- 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;
-
- ret = -EINVAL;
- mmap_write_lock(mm);
- vma_iter_init(&vmi, mm, start);
- vma = vma_find(&vmi, end);
- if (!vma)
- 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;
- cur = vma;
- do {
- cond_resched();
-
- VM_WARN_ON_ONCE(!!cur->vm_userfaultfd_ctx.ctx ^
- !!(cur->vm_flags & __VM_UFFD_FLAGS));
-
- /* check not compatible vmas */
- ret = -EINVAL;
- if (!vma_can_userfault(cur, vm_flags, wp_async))
- 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;
- }
- if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE))
- 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;
- } for_each_vma_range(vmi, cur, end);
- VM_WARN_ON_ONCE(!found);
-
- ret = userfaultfd_register_range(ctx, vma, vm_flags, start, end,
- wp_async);
-
-out_unlock:
- mmap_write_unlock(mm);
- mmput(mm);
- if (!ret) {
- __u64 ioctls_out;
-
- ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC :
- UFFD_API_RANGE_IOCTLS;
-
- /*
- * Declare the WP ioctl only if the WP mode is
- * specified and all checks passed with the range
- */
- if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP))
- ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT);
-
- /* CONTINUE ioctl is only supported for MINOR ranges. */
- if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR))
- ioctls_out &= ~((__u64)1 << _UFFDIO_CONTINUE);
-
- /*
- * Now that we scanned all vmas we can already tell
- * userland which ioctls methods are guaranteed to
- * succeed on this range.
- */
- if (put_user(ioctls_out, &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;
- bool found;
- unsigned long start, end, vma_end;
- const void __user *buf = (void __user *)arg;
- struct vma_iterator vmi;
- bool wp_async = userfaultfd_wp_async_ctx(ctx);
-
- 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;
-
- mmap_write_lock(mm);
- ret = -EINVAL;
- vma_iter_init(&vmi, mm, start);
- vma = vma_find(&vmi, end);
- if (!vma)
- 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;
- cur = vma;
- do {
- cond_resched();
-
- VM_WARN_ON_ONCE(!!cur->vm_userfaultfd_ctx.ctx ^
- !!(cur->vm_flags & __VM_UFFD_FLAGS));
-
- /*
- * Prevent unregistering through a different userfaultfd than
- * the one used for registration.
- */
- if (cur->vm_userfaultfd_ctx.ctx &&
- cur->vm_userfaultfd_ctx.ctx != ctx)
- goto out_unlock;
-
- /*
- * 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, cur->vm_flags, wp_async))
- goto out_unlock;
-
- found = true;
- } for_each_vma_range(vmi, cur, end);
- VM_WARN_ON_ONCE(!found);
-
- vma_iter_set(&vmi, start);
- prev = vma_prev(&vmi);
- if (vma->vm_start < start)
- prev = vma;
-
- ret = 0;
- for_each_vma_range(vmi, vma, end) {
- cond_resched();
-
- /* VMA not registered with userfaultfd. */
- if (!vma->vm_userfaultfd_ctx.ctx)
- goto skip;
-
- VM_WARN_ON_ONCE(vma->vm_userfaultfd_ctx.ctx != ctx);
- VM_WARN_ON_ONCE(!vma_can_userfault(vma, vma->vm_flags, wp_async));
- VM_WARN_ON_ONCE(!(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);
- }
-
- vma = userfaultfd_clear_vma(&vmi, prev, vma,
- start, vma_end);
- if (IS_ERR(vma)) {
- ret = PTR_ERR(vma);
- break;
- }
-
- skip:
- prev = vma;
- start = vma->vm_end;
- }
-
-out_unlock:
- mmap_write_unlock(mm);
- 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_WARN_ON_ONCE(!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;
- uffd_flags_t flags = 0;
-
- user_uffdio_copy = (struct uffdio_copy __user *) arg;
-
- ret = -EAGAIN;
- if (unlikely(atomic_read(&ctx->mmap_changing))) {
- if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
- return -EFAULT;
- 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_unaligned_range(ctx->mm, uffdio_copy.src,
- uffdio_copy.len);
- if (ret)
- goto out;
- ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
- if (ret)
- goto out;
-
- ret = -EINVAL;
- if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP))
- goto out;
- if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP)
- flags |= MFILL_ATOMIC_WP;
- if (mmget_not_zero(ctx->mm)) {
- ret = mfill_atomic_copy(ctx, uffdio_copy.dst, uffdio_copy.src,
- uffdio_copy.len, flags);
- mmput(ctx->mm);
- } else {
- return -ESRCH;
- }
- if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
- return -EFAULT;
- if (ret < 0)
- goto out;
- VM_WARN_ON_ONCE(!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 (unlikely(atomic_read(&ctx->mmap_changing))) {
- if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
- return -EFAULT;
- 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_atomic_zeropage(ctx, uffdio_zeropage.range.start,
- uffdio_zeropage.range.len);
- 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 */
- VM_WARN_ON_ONCE(!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 int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx,
- unsigned long arg)
-{
- int ret;
- struct uffdio_writeprotect uffdio_wp;
- struct uffdio_writeprotect __user *user_uffdio_wp;
- struct userfaultfd_wake_range range;
- bool mode_wp, mode_dontwake;
-
- if (atomic_read(&ctx->mmap_changing))
- return -EAGAIN;
-
- user_uffdio_wp = (struct uffdio_writeprotect __user *) arg;
-
- if (copy_from_user(&uffdio_wp, user_uffdio_wp,
- sizeof(struct uffdio_writeprotect)))
- return -EFAULT;
-
- ret = validate_range(ctx->mm, uffdio_wp.range.start,
- uffdio_wp.range.len);
- if (ret)
- return ret;
-
- if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE |
- UFFDIO_WRITEPROTECT_MODE_WP))
- return -EINVAL;
-
- mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP;
- mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE;
-
- if (mode_wp && mode_dontwake)
- return -EINVAL;
-
- if (mmget_not_zero(ctx->mm)) {
- ret = mwriteprotect_range(ctx, uffdio_wp.range.start,
- uffdio_wp.range.len, mode_wp);
- mmput(ctx->mm);
- } else {
- return -ESRCH;
- }
-
- if (ret)
- return ret;
-
- if (!mode_wp && !mode_dontwake) {
- range.start = uffdio_wp.range.start;
- range.len = uffdio_wp.range.len;
- wake_userfault(ctx, &range);
- }
- return ret;
-}
-
-static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg)
-{
- __s64 ret;
- struct uffdio_continue uffdio_continue;
- struct uffdio_continue __user *user_uffdio_continue;
- struct userfaultfd_wake_range range;
- uffd_flags_t flags = 0;
-
- user_uffdio_continue = (struct uffdio_continue __user *)arg;
-
- ret = -EAGAIN;
- if (unlikely(atomic_read(&ctx->mmap_changing))) {
- if (unlikely(put_user(ret, &user_uffdio_continue->mapped)))
- return -EFAULT;
- goto out;
- }
-
- ret = -EFAULT;
- if (copy_from_user(&uffdio_continue, user_uffdio_continue,
- /* don't copy the output fields */
- sizeof(uffdio_continue) - (sizeof(__s64))))
- goto out;
-
- ret = validate_range(ctx->mm, uffdio_continue.range.start,
- uffdio_continue.range.len);
- if (ret)
- goto out;
-
- ret = -EINVAL;
- if (uffdio_continue.mode & ~(UFFDIO_CONTINUE_MODE_DONTWAKE |
- UFFDIO_CONTINUE_MODE_WP))
- goto out;
- if (uffdio_continue.mode & UFFDIO_CONTINUE_MODE_WP)
- flags |= MFILL_ATOMIC_WP;
-
- if (mmget_not_zero(ctx->mm)) {
- ret = mfill_atomic_continue(ctx, uffdio_continue.range.start,
- uffdio_continue.range.len, flags);
- mmput(ctx->mm);
- } else {
- return -ESRCH;
- }
-
- if (unlikely(put_user(ret, &user_uffdio_continue->mapped)))
- return -EFAULT;
- if (ret < 0)
- goto out;
-
- /* len == 0 would wake all */
- VM_WARN_ON_ONCE(!ret);
- range.len = ret;
- if (!(uffdio_continue.mode & UFFDIO_CONTINUE_MODE_DONTWAKE)) {
- range.start = uffdio_continue.range.start;
- wake_userfault(ctx, &range);
- }
- ret = range.len == uffdio_continue.range.len ? 0 : -EAGAIN;
-
-out:
- return ret;
-}
-
-static inline int userfaultfd_poison(struct userfaultfd_ctx *ctx, unsigned long arg)
-{
- __s64 ret;
- struct uffdio_poison uffdio_poison;
- struct uffdio_poison __user *user_uffdio_poison;
- struct userfaultfd_wake_range range;
-
- user_uffdio_poison = (struct uffdio_poison __user *)arg;
-
- ret = -EAGAIN;
- if (unlikely(atomic_read(&ctx->mmap_changing))) {
- if (unlikely(put_user(ret, &user_uffdio_poison->updated)))
- return -EFAULT;
- goto out;
- }
-
- ret = -EFAULT;
- if (copy_from_user(&uffdio_poison, user_uffdio_poison,
- /* don't copy the output fields */
- sizeof(uffdio_poison) - (sizeof(__s64))))
- goto out;
-
- ret = validate_range(ctx->mm, uffdio_poison.range.start,
- uffdio_poison.range.len);
- if (ret)
- goto out;
-
- ret = -EINVAL;
- if (uffdio_poison.mode & ~UFFDIO_POISON_MODE_DONTWAKE)
- goto out;
-
- if (mmget_not_zero(ctx->mm)) {
- ret = mfill_atomic_poison(ctx, uffdio_poison.range.start,
- uffdio_poison.range.len, 0);
- mmput(ctx->mm);
- } else {
- return -ESRCH;
- }
-
- if (unlikely(put_user(ret, &user_uffdio_poison->updated)))
- return -EFAULT;
- if (ret < 0)
- goto out;
-
- /* len == 0 would wake all */
- VM_WARN_ON_ONCE(!ret);
- range.len = ret;
- if (!(uffdio_poison.mode & UFFDIO_POISON_MODE_DONTWAKE)) {
- range.start = uffdio_poison.range.start;
- wake_userfault(ctx, &range);
- }
- ret = range.len == uffdio_poison.range.len ? 0 : -EAGAIN;
-
-out:
- return ret;
-}
-
-bool userfaultfd_wp_async(struct vm_area_struct *vma)
-{
- return userfaultfd_wp_async_ctx(vma->vm_userfaultfd_ctx.ctx);
-}
-
-static inline unsigned int uffd_ctx_features(__u64 user_features)
-{
- /*
- * For the current set of features the bits just coincide. Set
- * UFFD_FEATURE_INITIALIZED to mark the features as enabled.
- */
- return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED;
-}
-
-static int userfaultfd_move(struct userfaultfd_ctx *ctx,
- unsigned long arg)
-{
- __s64 ret;
- struct uffdio_move uffdio_move;
- struct uffdio_move __user *user_uffdio_move;
- struct userfaultfd_wake_range range;
- struct mm_struct *mm = ctx->mm;
-
- user_uffdio_move = (struct uffdio_move __user *) arg;
-
- ret = -EAGAIN;
- if (unlikely(atomic_read(&ctx->mmap_changing))) {
- if (unlikely(put_user(ret, &user_uffdio_move->move)))
- return -EFAULT;
- goto out;
- }
-
- if (copy_from_user(&uffdio_move, user_uffdio_move,
- /* don't copy "move" last field */
- sizeof(uffdio_move)-sizeof(__s64)))
- return -EFAULT;
-
- /* Do not allow cross-mm moves. */
- if (mm != current->mm)
- return -EINVAL;
-
- ret = validate_range(mm, uffdio_move.dst, uffdio_move.len);
- if (ret)
- return ret;
-
- ret = validate_range(mm, uffdio_move.src, uffdio_move.len);
- if (ret)
- return ret;
-
- if (uffdio_move.mode & ~(UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES|
- UFFDIO_MOVE_MODE_DONTWAKE))
- return -EINVAL;
-
- if (mmget_not_zero(mm)) {
- ret = move_pages(ctx, uffdio_move.dst, uffdio_move.src,
- uffdio_move.len, uffdio_move.mode);
- mmput(mm);
- } else {
- return -ESRCH;
- }
-
- if (unlikely(put_user(ret, &user_uffdio_move->move)))
- return -EFAULT;
- if (ret < 0)
- goto out;
-
- /* len == 0 would wake all */
- VM_WARN_ON(!ret);
- range.len = ret;
- if (!(uffdio_move.mode & UFFDIO_MOVE_MODE_DONTWAKE)) {
- range.start = uffdio_move.dst;
- wake_userfault(ctx, &range);
- }
- ret = range.len == uffdio_move.len ? 0 : -EAGAIN;
-
-out:
- return ret;
-}
-
-/*
- * 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;
- unsigned int ctx_features;
- int ret;
- __u64 features;
-
- ret = -EFAULT;
- if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
- goto out;
- features = uffdio_api.features;
- ret = -EINVAL;
- if (uffdio_api.api != UFFD_API)
- goto err_out;
- ret = -EPERM;
- if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
- goto err_out;
-
- /* WP_ASYNC relies on WP_UNPOPULATED, choose it unconditionally */
- if (features & UFFD_FEATURE_WP_ASYNC)
- features |= UFFD_FEATURE_WP_UNPOPULATED;
-
- /* report all available features and ioctls to userland */
- uffdio_api.features = UFFD_API_FEATURES;
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
- uffdio_api.features &=
- ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM);
-#endif
- if (!pgtable_supports_uffd_wp())
- uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
-
- if (!uffd_supports_wp_marker()) {
- uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
- uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
- uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
- }
-
- ret = -EINVAL;
- if (features & ~uffdio_api.features)
- goto err_out;
-
- uffdio_api.ioctls = UFFD_API_IOCTLS;
- ret = -EFAULT;
- if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
- goto out;
-
- /* only enable the requested features for this uffd context */
- ctx_features = uffd_ctx_features(features);
- ret = -EINVAL;
- if (cmpxchg(&ctx->features, 0, ctx_features) != 0)
- goto err_out;
-
- ret = 0;
-out:
- return ret;
-err_out:
- memset(&uffdio_api, 0, sizeof(uffdio_api));
- if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
- ret = -EFAULT;
- goto out;
-}
-
-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 && !userfaultfd_is_initialized(ctx))
- 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;
- case UFFDIO_MOVE:
- ret = userfaultfd_move(ctx, arg);
- break;
- case UFFDIO_WRITEPROTECT:
- ret = userfaultfd_writeprotect(ctx, arg);
- break;
- case UFFDIO_CONTINUE:
- ret = userfaultfd_continue(ctx, arg);
- break;
- case UFFDIO_POISON:
- ret = userfaultfd_poison(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_iter = userfaultfd_read_iter,
- .unlocked_ioctl = userfaultfd_ioctl,
- .compat_ioctl = compat_ptr_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_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock);
-}
-
-static int new_userfaultfd(int flags)
-{
- struct userfaultfd_ctx *ctx __free(kfree) = NULL;
-
- VM_WARN_ON_ONCE(!current->mm);
-
- /* Check the UFFD_* constants for consistency. */
- BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS);
-
- if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY))
- 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->released = false;
- init_rwsem(&ctx->map_changing_lock);
- atomic_set(&ctx->mmap_changing, 0);
- ctx->mm = current->mm;
-
- FD_PREPARE(fdf, flags & UFFD_SHARED_FCNTL_FLAGS,
- anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
- O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS),
- NULL));
- if (fdf.err)
- return fdf.err;
-
- /* prevent the mm struct to be freed */
- mmgrab(ctx->mm);
- fd_prepare_file(fdf)->f_mode |= FMODE_NOWAIT;
- retain_and_null_ptr(ctx);
- return fd_publish(fdf);
-}
-
-static inline bool userfaultfd_syscall_allowed(int flags)
-{
- /* Userspace-only page faults are always allowed */
- if (flags & UFFD_USER_MODE_ONLY)
- return true;
-
- /*
- * The user is requesting a userfaultfd which can handle kernel faults.
- * Privileged users are always allowed to do this.
- */
- if (capable(CAP_SYS_PTRACE))
- return true;
-
- /* Otherwise, access to kernel fault handling is sysctl controlled. */
- return sysctl_unprivileged_userfaultfd;
-}
-
-SYSCALL_DEFINE1(userfaultfd, int, flags)
-{
- if (!userfaultfd_syscall_allowed(flags))
- return -EPERM;
-
- return new_userfaultfd(flags);
-}
-
-static long userfaultfd_dev_ioctl(struct file *file, unsigned int cmd, unsigned long flags)
-{
- if (cmd != USERFAULTFD_IOC_NEW)
- return -EINVAL;
-
- return new_userfaultfd(flags);
-}
-
-static const struct file_operations userfaultfd_dev_fops = {
- .unlocked_ioctl = userfaultfd_dev_ioctl,
- .compat_ioctl = userfaultfd_dev_ioctl,
- .owner = THIS_MODULE,
- .llseek = noop_llseek,
-};
-
-static struct miscdevice userfaultfd_misc = {
- .minor = MISC_DYNAMIC_MINOR,
- .name = "userfaultfd",
- .fops = &userfaultfd_dev_fops
-};
-
-static int __init userfaultfd_init(void)
-{
- int ret;
-
- ret = misc_register(&userfaultfd_misc);
- if (ret)
- return ret;
-
- userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
- sizeof(struct userfaultfd_ctx),
- 0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC,
- init_once_userfaultfd_ctx);
-#ifdef CONFIG_SYSCTL
- register_sysctl_init("vm", vm_userfaultfd_table);
-#endif
- return 0;
-}
-__initcall(userfaultfd_init);
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 885da1e56466..720690f058d7 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -2,7 +2,12 @@
/*
* mm/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/mm.h>
@@ -14,6 +19,18 @@
#include <linux/userfaultfd_k.h>
#include <linux/mmu_notifier.h>
#include <linux/hugetlb.h>
+#include <linux/list.h>
+#include <linux/sched/mm.h>
+#include <linux/mm_inline.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/miscdevice.h>
+#include <linux/uio.h>
#include <asm/tlbflush.h>
#include <asm/tlb.h>
#include "internal.h"
@@ -2229,3 +2246,2201 @@ void userfaultfd_release_all(struct mm_struct *mm,
mmap_write_unlock(mm);
mmput(mm);
}
+
+static int sysctl_unprivileged_userfaultfd __read_mostly;
+
+#ifdef CONFIG_SYSCTL
+static const struct ctl_table vm_userfaultfd_table[] = {
+ {
+ .procname = "unprivileged_userfaultfd",
+ .data = &sysctl_unprivileged_userfaultfd,
+ .maxlen = sizeof(sysctl_unprivileged_userfaultfd),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
+};
+#endif
+
+static struct kmem_cache *userfaultfd_ctx_cachep __ro_after_init;
+
+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;
+};
+
+/* internal indication that UFFD_API ioctl was successfully executed */
+#define UFFD_FEATURE_INITIALIZED (1u << 31)
+
+static bool userfaultfd_is_initialized(struct userfaultfd_ctx *ctx)
+{
+ return ctx->features & UFFD_FEATURE_INITIALIZED;
+}
+
+static bool userfaultfd_wp_async_ctx(struct userfaultfd_ctx *ctx)
+{
+ return ctx && (ctx->features & UFFD_FEATURE_WP_ASYNC);
+}
+
+/*
+ * Whether WP_UNPOPULATED is enabled on the uffd context. It is only
+ * meaningful when userfaultfd_wp()==true on the vma and when it's
+ * anonymous.
+ */
+bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma)
+{
+ struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
+
+ if (!ctx)
+ return false;
+
+ return ctx->features & UFFD_FEATURE_WP_UNPOPULATED;
+}
+
+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_WARN_ON_ONCE(spin_is_locked(&ctx->fault_pending_wqh.lock));
+ VM_WARN_ON_ONCE(waitqueue_active(&ctx->fault_pending_wqh));
+ VM_WARN_ON_ONCE(spin_is_locked(&ctx->fault_wqh.lock));
+ VM_WARN_ON_ONCE(waitqueue_active(&ctx->fault_wqh));
+ VM_WARN_ON_ONCE(spin_is_locked(&ctx->event_wqh.lock));
+ VM_WARN_ON_ONCE(waitqueue_active(&ctx->event_wqh));
+ VM_WARN_ON_ONCE(spin_is_locked(&ctx->fd_wqh.lock));
+ VM_WARN_ON_ONCE(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 long real_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 = (features & UFFD_FEATURE_EXACT_ADDRESS) ?
+ real_address : address;
+
+ /*
+ * These flags indicate why the userfault occurred:
+ * - UFFD_PAGEFAULT_FLAG_WP indicates a write protect fault.
+ * - UFFD_PAGEFAULT_FLAG_MINOR indicates a minor fault.
+ * - Neither of these flags being set indicates a MISSING fault.
+ *
+ * Separately, UFFD_PAGEFAULT_FLAG_WRITE indicates it was a write
+ * fault. Otherwise, it was a read fault.
+ */
+ if (flags & FAULT_FLAG_WRITE)
+ msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
+ if (reason & VM_UFFD_WP)
+ msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
+ if (reason & VM_UFFD_MINOR)
+ msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_MINOR;
+ 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_fault *vmf,
+ unsigned long reason)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ pte_t *ptep, pte;
+
+ assert_fault_locked(vmf);
+
+ ptep = hugetlb_walk(vma, vmf->address, vma_mmu_pagesize(vma));
+ if (!ptep)
+ return true;
+
+ pte = huge_ptep_get(vma->vm_mm, vmf->address, ptep);
+
+ /*
+ * Lockless access: we're in a wait_event so it's ok if it
+ * changes under us.
+ */
+
+ /* Entry is still missing, wait for userspace to resolve the fault. */
+ if (huge_pte_none(pte))
+ return true;
+ /* UFFD PTE markers require userspace to resolve the fault. */
+ if (pte_is_uffd_marker(pte))
+ return true;
+ /*
+ * If VMA has UFFD WP faults enabled and WP fault, wait for userspace to
+ * resolve the fault.
+ */
+ if (!huge_pte_write(pte) && (reason & VM_UFFD_WP))
+ return true;
+
+ return false;
+}
+#else
+static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
+ struct vm_fault *vmf,
+ unsigned long reason)
+{
+ /* Should never get here. */
+ VM_WARN_ON_ONCE(1);
+ return false;
+}
+#endif /* CONFIG_HUGETLB_PAGE */
+
+/*
+ * Verify the pagetables are still not ok after having registered into
+ * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any
+ * userfault that has already been resolved, if userfaultfd_read_iter and
+ * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different
+ * threads.
+ */
+static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
+ struct vm_fault *vmf,
+ unsigned long reason)
+{
+ struct mm_struct *mm = ctx->mm;
+ unsigned long address = vmf->address;
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd, _pmd;
+ pte_t *pte;
+ pte_t ptent;
+ bool ret;
+
+ assert_fault_locked(vmf);
+
+ pgd = pgd_offset(mm, address);
+ if (!pgd_present(*pgd))
+ return true;
+ p4d = p4d_offset(pgd, address);
+ if (!p4d_present(*p4d))
+ return true;
+ pud = pud_offset(p4d, address);
+ if (!pud_present(*pud))
+ return true;
+ pmd = pmd_offset(pud, address);
+again:
+ _pmd = pmdp_get_lockless(pmd);
+ if (pmd_none(_pmd))
+ return true;
+
+ /*
+ * A race could arise which would result in a softleaf entry such as
+ * migration entry unexpectedly being present in the PMD, so explicitly
+ * check for this and bail out if so.
+ */
+ if (!pmd_present(_pmd))
+ return false;
+
+ if (pmd_trans_huge(_pmd))
+ return !pmd_write(_pmd) && (reason & VM_UFFD_WP);
+
+ pte = pte_offset_map(pmd, address);
+ if (!pte)
+ goto again;
+
+ /*
+ * Lockless access: we're in a wait_event so it's ok if it
+ * changes under us.
+ */
+ ptent = ptep_get(pte);
+
+ ret = true;
+ /* Entry is still missing, wait for userspace to resolve the fault. */
+ if (pte_none(ptent))
+ goto out;
+ /* UFFD PTE markers require userspace to resolve the fault. */
+ if (pte_is_uffd_marker(ptent))
+ goto out;
+ /*
+ * If VMA has UFFD WP faults enabled and WP fault, wait for userspace to
+ * resolve the fault.
+ */
+ if (!pte_write(ptent) && (reason & VM_UFFD_WP))
+ goto out;
+
+ ret = false;
+out:
+ pte_unmap(pte);
+ return ret;
+}
+
+static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags)
+{
+ if (flags & FAULT_FLAG_INTERRUPTIBLE)
+ return TASK_INTERRUPTIBLE;
+
+ if (flags & FAULT_FLAG_KILLABLE)
+ return TASK_KILLABLE;
+
+ return TASK_UNINTERRUPTIBLE;
+}
+
+/*
+ * 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_lock 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_lock must be released before
+ * returning it.
+ */
+vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct mm_struct *mm = vma->vm_mm;
+ struct userfaultfd_ctx *ctx;
+ struct userfaultfd_wait_queue uwq;
+ vm_fault_t ret = VM_FAULT_SIGBUS;
+ bool must_wait;
+ unsigned int blocking_state;
+
+ /*
+ * We don't do userfault handling for the final child pid update
+ * and when coredumping (faults triggered by get_dump_page()).
+ */
+ if (current->flags & (PF_EXITING|PF_DUMPCORE))
+ goto out;
+
+ assert_fault_locked(vmf);
+
+ ctx = vma->vm_userfaultfd_ctx.ctx;
+ if (!ctx)
+ goto out;
+
+ VM_WARN_ON_ONCE(ctx->mm != mm);
+
+ /* Any unrecognized flag is a bug. */
+ VM_WARN_ON_ONCE(reason & ~__VM_UFFD_FLAGS);
+ /* 0 or > 1 flags set is a bug; we expect exactly 1. */
+ VM_WARN_ON_ONCE(!reason || (reason & (reason - 1)));
+
+ if (ctx->features & UFFD_FEATURE_SIGBUS)
+ goto out;
+ if (!(vmf->flags & FAULT_FLAG_USER) && (ctx->flags & UFFD_USER_MODE_ONLY))
+ 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.
+ */
+ VM_WARN_ON_ONCE(vmf->flags & FAULT_FLAG_RETRY_NOWAIT);
+#ifdef CONFIG_DEBUG_VM
+ if (printk_ratelimit()) {
+ pr_warn("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;
+
+ if (unlikely(READ_ONCE(ctx->released))) {
+ /*
+ * If a concurrent release is detected, do not return
+ * VM_FAULT_SIGBUS or VM_FAULT_NOPAGE, but instead always
+ * return VM_FAULT_RETRY with lock released proactively.
+ *
+ * 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, to avoid involuntary SIGBUS triggered.
+ *
+ * If we were to return VM_FAULT_NOPAGE, it would work for
+ * the fault path, in which the lock will be released
+ * later. However for GUP, faultin_page() does nothing
+ * special on NOPAGE, so GUP would spin retrying without
+ * releasing the mmap read lock, causing possible livelock.
+ *
+ * Here only VM_FAULT_RETRY would make sure the mmap lock
+ * be released immediately, so that the thread concurrently
+ * releasing the userfault would always make progress.
+ */
+ release_fault_lock(vmf);
+ goto out;
+ }
+
+ /* take the reference before dropping the mmap_lock */
+ userfaultfd_ctx_get(ctx);
+
+ init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
+ uwq.wq.private = current;
+ uwq.msg = userfault_msg(vmf->address, vmf->real_address, vmf->flags,
+ reason, ctx->features);
+ uwq.ctx = ctx;
+ uwq.waken = false;
+
+ blocking_state = userfaultfd_get_blocking_state(vmf->flags);
+
+ /*
+ * Take the vma lock now, in order to safely call
+ * userfaultfd_huge_must_wait() later. Since acquiring the
+ * (sleepable) vma lock can modify the current task state, that
+ * must be before explicitly calling set_current_state().
+ */
+ if (is_vm_hugetlb_page(vma))
+ hugetlb_vma_lock_read(vma);
+
+ 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(vma)) {
+ must_wait = userfaultfd_huge_must_wait(ctx, vmf, reason);
+ hugetlb_vma_unlock_read(vma);
+ } else {
+ must_wait = userfaultfd_must_wait(ctx, vmf, reason);
+ }
+
+ release_fault_lock(vmf);
+
+ if (likely(must_wait && !READ_ONCE(ctx->released))) {
+ wake_up_poll(&ctx->fd_wqh, EPOLLIN);
+ schedule();
+ }
+
+ __set_current_state(TASK_RUNNING);
+
+ /*
+ * 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) {
+ userfaultfd_release_new(release_new_ctx);
+ userfaultfd_ctx_put(release_new_ctx);
+ }
+
+ /*
+ * ctx may go away after this if the userfault pseudo fd is
+ * already released.
+ */
+out:
+ atomic_dec(&ctx->mmap_changing);
+ VM_WARN_ON_ONCE(atomic_read(&ctx->mmap_changing) < 0);
+ 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)
+ return 0;
+
+ if (!(octx->features & UFFD_FEATURE_EVENT_FORK)) {
+ userfaultfd_reset_ctx(vma);
+ return 0;
+ }
+
+ list_for_each_entry(fctx, fcs, list)
+ if (fctx->orig == octx) {
+ ctx = fctx->new;
+ break;
+ }
+
+ if (!ctx) {
+ fctx = kmalloc_obj(*fctx);
+ 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->features = octx->features;
+ ctx->released = false;
+ init_rwsem(&ctx->map_changing_lock);
+ atomic_set(&ctx->mmap_changing, 0);
+ ctx->mm = vma->vm_mm;
+ mmgrab(ctx->mm);
+
+ userfaultfd_ctx_get(octx);
+ down_write(&octx->map_changing_lock);
+ atomic_inc(&octx->mmap_changing);
+ up_write(&octx->map_changing_lock);
+ 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 dup_userfaultfd_fail(struct list_head *fcs)
+{
+ struct userfaultfd_fork_ctx *fctx, *n;
+
+ /*
+ * An error has occurred on fork, we will tear memory down, but have
+ * allocated memory for fctx's and raised reference counts for both the
+ * original and child contexts (and on the mm for each as a result).
+ *
+ * These would ordinarily be taken care of by a user handling the event,
+ * but we are no longer doing so, so manually clean up here.
+ *
+ * mm tear down will take care of cleaning up VMA contexts.
+ */
+ list_for_each_entry_safe(fctx, n, fcs, list) {
+ struct userfaultfd_ctx *octx = fctx->orig;
+ struct userfaultfd_ctx *ctx = fctx->new;
+
+ atomic_dec(&octx->mmap_changing);
+ VM_WARN_ON_ONCE(atomic_read(&octx->mmap_changing) < 0);
+ userfaultfd_ctx_put(octx);
+ userfaultfd_ctx_put(ctx);
+
+ 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);
+ down_write(&ctx->map_changing_lock);
+ atomic_inc(&ctx->mmap_changing);
+ up_write(&ctx->map_changing_lock);
+ } else {
+ /* Drop uffd context if remap feature not enabled */
+ userfaultfd_reset_ctx(vma);
+ }
+}
+
+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;
+
+ 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);
+}
+
+void mremap_userfaultfd_fail(struct vm_userfaultfd_ctx *vm_ctx)
+{
+ struct userfaultfd_ctx *ctx = vm_ctx->ctx;
+
+ if (!ctx)
+ return;
+
+ atomic_dec(&ctx->mmap_changing);
+ userfaultfd_ctx_put(ctx);
+}
+
+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);
+ down_write(&ctx->map_changing_lock);
+ atomic_inc(&ctx->mmap_changing);
+ up_write(&ctx->map_changing_lock);
+ mmap_read_unlock(mm);
+
+ 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)
+{
+ 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))
+ return 0;
+
+ unmap_ctx = kzalloc_obj(*unmap_ctx);
+ if (!unmap_ctx)
+ return -ENOMEM;
+
+ userfaultfd_ctx_get(ctx);
+ down_write(&ctx->map_changing_lock);
+ atomic_inc(&ctx->mmap_changing);
+ up_write(&ctx->map_changing_lock);
+ 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;
+ /* len == 0 means wake all */
+ struct userfaultfd_wake_range range = { .len = 0, };
+
+ WRITE_ONCE(ctx->released, true);
+
+ userfaultfd_release_all(mm, ctx);
+
+ /*
+ * 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);
+
+ if (!userfaultfd_is_initialized(ctx))
+ return EPOLLERR;
+
+ /*
+ * 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;
+}
+
+static const struct file_operations userfaultfd_fops;
+
+static int resolve_userfault_fork(struct userfaultfd_ctx *new,
+ struct inode *inode,
+ struct uffd_msg *msg)
+{
+ int fd;
+
+ fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, new,
+ O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode);
+ 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, struct inode *inode)
+{
+ 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(fork_nctx, inode, 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_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ struct file *file = iocb->ki_filp;
+ struct userfaultfd_ctx *ctx = file->private_data;
+ ssize_t _ret, ret = 0;
+ struct uffd_msg msg;
+ struct inode *inode = file_inode(file);
+ bool no_wait;
+
+ if (!userfaultfd_is_initialized(ctx))
+ return -EINVAL;
+
+ no_wait = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT;
+ for (;;) {
+ if (iov_iter_count(to) < sizeof(msg))
+ return ret ? ret : -EINVAL;
+ _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode);
+ if (_ret < 0)
+ return ret ? ret : _ret;
+ _ret = !copy_to_iter_full(&msg, sizeof(msg), to);
+ if (_ret)
+ return ret ? ret : -EFAULT;
+ ret += sizeof(msg);
+ /*
+ * Allow to read more than one fault at time but only
+ * block if waiting for the very first one.
+ */
+ no_wait = true;
+ }
+}
+
+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 mmap_read_unlock(mm) 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_unaligned_range(
+ struct mm_struct *mm, __u64 start, __u64 len)
+{
+ __u64 task_size = mm->task_size;
+
+ if (len & ~PAGE_MASK)
+ return -EINVAL;
+ if (!len)
+ return -EINVAL;
+ if (start >= task_size)
+ return -EINVAL;
+ if (len > task_size - start)
+ return -EINVAL;
+ if (start + len <= start)
+ return -EINVAL;
+ return 0;
+}
+
+static __always_inline int validate_range(struct mm_struct *mm,
+ __u64 start, __u64 len)
+{
+ if (start & ~PAGE_MASK)
+ return -EINVAL;
+
+ return validate_unaligned_range(mm, start, len);
+}
+
+static int userfaultfd_register(struct userfaultfd_ctx *ctx,
+ unsigned long arg)
+{
+ struct mm_struct *mm = ctx->mm;
+ struct vm_area_struct *vma, *cur;
+ int ret;
+ struct uffdio_register uffdio_register;
+ struct uffdio_register __user *user_uffdio_register;
+ vm_flags_t vm_flags;
+ bool found;
+ bool basic_ioctls;
+ unsigned long start, end;
+ struct vma_iterator vmi;
+ bool wp_async = userfaultfd_wp_async_ctx(ctx);
+
+ 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 & ~UFFD_API_REGISTER_MODES)
+ 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) {
+ if (!pgtable_supports_uffd_wp())
+ goto out;
+
+ vm_flags |= VM_UFFD_WP;
+ }
+ if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
+#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
+ goto out;
+#endif
+ vm_flags |= VM_UFFD_MINOR;
+ }
+
+ 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;
+
+ ret = -EINVAL;
+ mmap_write_lock(mm);
+ vma_iter_init(&vmi, mm, start);
+ vma = vma_find(&vmi, end);
+ if (!vma)
+ 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;
+ cur = vma;
+ do {
+ cond_resched();
+
+ VM_WARN_ON_ONCE(!!cur->vm_userfaultfd_ctx.ctx ^
+ !!(cur->vm_flags & __VM_UFFD_FLAGS));
+
+ /* check not compatible vmas */
+ ret = -EINVAL;
+ if (!vma_can_userfault(cur, vm_flags, wp_async))
+ 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;
+ }
+ if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE))
+ 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;
+ } for_each_vma_range(vmi, cur, end);
+ VM_WARN_ON_ONCE(!found);
+
+ ret = userfaultfd_register_range(ctx, vma, vm_flags, start, end,
+ wp_async);
+
+out_unlock:
+ mmap_write_unlock(mm);
+ mmput(mm);
+ if (!ret) {
+ __u64 ioctls_out;
+
+ ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC :
+ UFFD_API_RANGE_IOCTLS;
+
+ /*
+ * Declare the WP ioctl only if the WP mode is
+ * specified and all checks passed with the range
+ */
+ if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP))
+ ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT);
+
+ /* CONTINUE ioctl is only supported for MINOR ranges. */
+ if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR))
+ ioctls_out &= ~((__u64)1 << _UFFDIO_CONTINUE);
+
+ /*
+ * Now that we scanned all vmas we can already tell
+ * userland which ioctls methods are guaranteed to
+ * succeed on this range.
+ */
+ if (put_user(ioctls_out, &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;
+ bool found;
+ unsigned long start, end, vma_end;
+ const void __user *buf = (void __user *)arg;
+ struct vma_iterator vmi;
+ bool wp_async = userfaultfd_wp_async_ctx(ctx);
+
+ 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;
+
+ mmap_write_lock(mm);
+ ret = -EINVAL;
+ vma_iter_init(&vmi, mm, start);
+ vma = vma_find(&vmi, end);
+ if (!vma)
+ 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;
+ cur = vma;
+ do {
+ cond_resched();
+
+ VM_WARN_ON_ONCE(!!cur->vm_userfaultfd_ctx.ctx ^
+ !!(cur->vm_flags & __VM_UFFD_FLAGS));
+
+ /*
+ * Prevent unregistering through a different userfaultfd than
+ * the one used for registration.
+ */
+ if (cur->vm_userfaultfd_ctx.ctx &&
+ cur->vm_userfaultfd_ctx.ctx != ctx)
+ goto out_unlock;
+
+ /*
+ * 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, cur->vm_flags, wp_async))
+ goto out_unlock;
+
+ found = true;
+ } for_each_vma_range(vmi, cur, end);
+ VM_WARN_ON_ONCE(!found);
+
+ vma_iter_set(&vmi, start);
+ prev = vma_prev(&vmi);
+ if (vma->vm_start < start)
+ prev = vma;
+
+ ret = 0;
+ for_each_vma_range(vmi, vma, end) {
+ cond_resched();
+
+ /* VMA not registered with userfaultfd. */
+ if (!vma->vm_userfaultfd_ctx.ctx)
+ goto skip;
+
+ VM_WARN_ON_ONCE(vma->vm_userfaultfd_ctx.ctx != ctx);
+ VM_WARN_ON_ONCE(!vma_can_userfault(vma, vma->vm_flags, wp_async));
+ VM_WARN_ON_ONCE(!(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);
+ }
+
+ vma = userfaultfd_clear_vma(&vmi, prev, vma,
+ start, vma_end);
+ if (IS_ERR(vma)) {
+ ret = PTR_ERR(vma);
+ break;
+ }
+
+skip:
+ prev = vma;
+ start = vma->vm_end;
+ }
+
+out_unlock:
+ mmap_write_unlock(mm);
+ 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_WARN_ON_ONCE(!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;
+ uffd_flags_t flags = 0;
+
+ user_uffdio_copy = (struct uffdio_copy __user *) arg;
+
+ ret = -EAGAIN;
+ if (unlikely(atomic_read(&ctx->mmap_changing))) {
+ if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
+ return -EFAULT;
+ 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_unaligned_range(ctx->mm, uffdio_copy.src,
+ uffdio_copy.len);
+ if (ret)
+ goto out;
+ ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
+ if (ret)
+ goto out;
+
+ ret = -EINVAL;
+ if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP))
+ goto out;
+ if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP)
+ flags |= MFILL_ATOMIC_WP;
+ if (mmget_not_zero(ctx->mm)) {
+ ret = mfill_atomic_copy(ctx, uffdio_copy.dst, uffdio_copy.src,
+ uffdio_copy.len, flags);
+ mmput(ctx->mm);
+ } else {
+ return -ESRCH;
+ }
+ if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
+ return -EFAULT;
+ if (ret < 0)
+ goto out;
+ VM_WARN_ON_ONCE(!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 (unlikely(atomic_read(&ctx->mmap_changing))) {
+ if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
+ return -EFAULT;
+ 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_atomic_zeropage(ctx, uffdio_zeropage.range.start,
+ uffdio_zeropage.range.len);
+ 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 */
+ VM_WARN_ON_ONCE(!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 int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx,
+ unsigned long arg)
+{
+ int ret;
+ struct uffdio_writeprotect uffdio_wp;
+ struct uffdio_writeprotect __user *user_uffdio_wp;
+ struct userfaultfd_wake_range range;
+ bool mode_wp, mode_dontwake;
+
+ if (atomic_read(&ctx->mmap_changing))
+ return -EAGAIN;
+
+ user_uffdio_wp = (struct uffdio_writeprotect __user *) arg;
+
+ if (copy_from_user(&uffdio_wp, user_uffdio_wp,
+ sizeof(struct uffdio_writeprotect)))
+ return -EFAULT;
+
+ ret = validate_range(ctx->mm, uffdio_wp.range.start,
+ uffdio_wp.range.len);
+ if (ret)
+ return ret;
+
+ if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE |
+ UFFDIO_WRITEPROTECT_MODE_WP))
+ return -EINVAL;
+
+ mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP;
+ mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE;
+
+ if (mode_wp && mode_dontwake)
+ return -EINVAL;
+
+ if (mmget_not_zero(ctx->mm)) {
+ ret = mwriteprotect_range(ctx, uffdio_wp.range.start,
+ uffdio_wp.range.len, mode_wp);
+ mmput(ctx->mm);
+ } else {
+ return -ESRCH;
+ }
+
+ if (ret)
+ return ret;
+
+ if (!mode_wp && !mode_dontwake) {
+ range.start = uffdio_wp.range.start;
+ range.len = uffdio_wp.range.len;
+ wake_userfault(ctx, &range);
+ }
+ return ret;
+}
+
+static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg)
+{
+ __s64 ret;
+ struct uffdio_continue uffdio_continue;
+ struct uffdio_continue __user *user_uffdio_continue;
+ struct userfaultfd_wake_range range;
+ uffd_flags_t flags = 0;
+
+ user_uffdio_continue = (struct uffdio_continue __user *)arg;
+
+ ret = -EAGAIN;
+ if (unlikely(atomic_read(&ctx->mmap_changing))) {
+ if (unlikely(put_user(ret, &user_uffdio_continue->mapped)))
+ return -EFAULT;
+ goto out;
+ }
+
+ ret = -EFAULT;
+ if (copy_from_user(&uffdio_continue, user_uffdio_continue,
+ /* don't copy the output fields */
+ sizeof(uffdio_continue) - (sizeof(__s64))))
+ goto out;
+
+ ret = validate_range(ctx->mm, uffdio_continue.range.start,
+ uffdio_continue.range.len);
+ if (ret)
+ goto out;
+
+ ret = -EINVAL;
+ if (uffdio_continue.mode & ~(UFFDIO_CONTINUE_MODE_DONTWAKE |
+ UFFDIO_CONTINUE_MODE_WP))
+ goto out;
+ if (uffdio_continue.mode & UFFDIO_CONTINUE_MODE_WP)
+ flags |= MFILL_ATOMIC_WP;
+
+ if (mmget_not_zero(ctx->mm)) {
+ ret = mfill_atomic_continue(ctx, uffdio_continue.range.start,
+ uffdio_continue.range.len, flags);
+ mmput(ctx->mm);
+ } else {
+ return -ESRCH;
+ }
+
+ if (unlikely(put_user(ret, &user_uffdio_continue->mapped)))
+ return -EFAULT;
+ if (ret < 0)
+ goto out;
+
+ /* len == 0 would wake all */
+ VM_WARN_ON_ONCE(!ret);
+ range.len = ret;
+ if (!(uffdio_continue.mode & UFFDIO_CONTINUE_MODE_DONTWAKE)) {
+ range.start = uffdio_continue.range.start;
+ wake_userfault(ctx, &range);
+ }
+ ret = range.len == uffdio_continue.range.len ? 0 : -EAGAIN;
+
+out:
+ return ret;
+}
+
+static inline int userfaultfd_poison(struct userfaultfd_ctx *ctx, unsigned long arg)
+{
+ __s64 ret;
+ struct uffdio_poison uffdio_poison;
+ struct uffdio_poison __user *user_uffdio_poison;
+ struct userfaultfd_wake_range range;
+
+ user_uffdio_poison = (struct uffdio_poison __user *)arg;
+
+ ret = -EAGAIN;
+ if (unlikely(atomic_read(&ctx->mmap_changing))) {
+ if (unlikely(put_user(ret, &user_uffdio_poison->updated)))
+ return -EFAULT;
+ goto out;
+ }
+
+ ret = -EFAULT;
+ if (copy_from_user(&uffdio_poison, user_uffdio_poison,
+ /* don't copy the output fields */
+ sizeof(uffdio_poison) - (sizeof(__s64))))
+ goto out;
+
+ ret = validate_range(ctx->mm, uffdio_poison.range.start,
+ uffdio_poison.range.len);
+ if (ret)
+ goto out;
+
+ ret = -EINVAL;
+ if (uffdio_poison.mode & ~UFFDIO_POISON_MODE_DONTWAKE)
+ goto out;
+
+ if (mmget_not_zero(ctx->mm)) {
+ ret = mfill_atomic_poison(ctx, uffdio_poison.range.start,
+ uffdio_poison.range.len, 0);
+ mmput(ctx->mm);
+ } else {
+ return -ESRCH;
+ }
+
+ if (unlikely(put_user(ret, &user_uffdio_poison->updated)))
+ return -EFAULT;
+ if (ret < 0)
+ goto out;
+
+ /* len == 0 would wake all */
+ VM_WARN_ON_ONCE(!ret);
+ range.len = ret;
+ if (!(uffdio_poison.mode & UFFDIO_POISON_MODE_DONTWAKE)) {
+ range.start = uffdio_poison.range.start;
+ wake_userfault(ctx, &range);
+ }
+ ret = range.len == uffdio_poison.range.len ? 0 : -EAGAIN;
+
+out:
+ return ret;
+}
+
+bool userfaultfd_wp_async(struct vm_area_struct *vma)
+{
+ return userfaultfd_wp_async_ctx(vma->vm_userfaultfd_ctx.ctx);
+}
+
+static inline unsigned int uffd_ctx_features(__u64 user_features)
+{
+ /*
+ * For the current set of features the bits just coincide. Set
+ * UFFD_FEATURE_INITIALIZED to mark the features as enabled.
+ */
+ return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED;
+}
+
+static int userfaultfd_move(struct userfaultfd_ctx *ctx,
+ unsigned long arg)
+{
+ __s64 ret;
+ struct uffdio_move uffdio_move;
+ struct uffdio_move __user *user_uffdio_move;
+ struct userfaultfd_wake_range range;
+ struct mm_struct *mm = ctx->mm;
+
+ user_uffdio_move = (struct uffdio_move __user *) arg;
+
+ ret = -EAGAIN;
+ if (unlikely(atomic_read(&ctx->mmap_changing))) {
+ if (unlikely(put_user(ret, &user_uffdio_move->move)))
+ return -EFAULT;
+ goto out;
+ }
+
+ if (copy_from_user(&uffdio_move, user_uffdio_move,
+ /* don't copy "move" last field */
+ sizeof(uffdio_move)-sizeof(__s64)))
+ return -EFAULT;
+
+ /* Do not allow cross-mm moves. */
+ if (mm != current->mm)
+ return -EINVAL;
+
+ ret = validate_range(mm, uffdio_move.dst, uffdio_move.len);
+ if (ret)
+ return ret;
+
+ ret = validate_range(mm, uffdio_move.src, uffdio_move.len);
+ if (ret)
+ return ret;
+
+ if (uffdio_move.mode & ~(UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES|
+ UFFDIO_MOVE_MODE_DONTWAKE))
+ return -EINVAL;
+
+ if (mmget_not_zero(mm)) {
+ ret = move_pages(ctx, uffdio_move.dst, uffdio_move.src,
+ uffdio_move.len, uffdio_move.mode);
+ mmput(mm);
+ } else {
+ return -ESRCH;
+ }
+
+ if (unlikely(put_user(ret, &user_uffdio_move->move)))
+ return -EFAULT;
+ if (ret < 0)
+ goto out;
+
+ /* len == 0 would wake all */
+ VM_WARN_ON(!ret);
+ range.len = ret;
+ if (!(uffdio_move.mode & UFFDIO_MOVE_MODE_DONTWAKE)) {
+ range.start = uffdio_move.dst;
+ wake_userfault(ctx, &range);
+ }
+ ret = range.len == uffdio_move.len ? 0 : -EAGAIN;
+
+out:
+ return ret;
+}
+
+/*
+ * 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;
+ unsigned int ctx_features;
+ int ret;
+ __u64 features;
+
+ ret = -EFAULT;
+ if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
+ goto out;
+ features = uffdio_api.features;
+ ret = -EINVAL;
+ if (uffdio_api.api != UFFD_API)
+ goto err_out;
+ ret = -EPERM;
+ if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
+ goto err_out;
+
+ /* WP_ASYNC relies on WP_UNPOPULATED, choose it unconditionally */
+ if (features & UFFD_FEATURE_WP_ASYNC)
+ features |= UFFD_FEATURE_WP_UNPOPULATED;
+
+ /* report all available features and ioctls to userland */
+ uffdio_api.features = UFFD_API_FEATURES;
+#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
+ uffdio_api.features &=
+ ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM);
+#endif
+ if (!pgtable_supports_uffd_wp())
+ uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+
+ if (!uffd_supports_wp_marker()) {
+ uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
+ uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
+ uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
+ }
+
+ ret = -EINVAL;
+ if (features & ~uffdio_api.features)
+ goto err_out;
+
+ uffdio_api.ioctls = UFFD_API_IOCTLS;
+ ret = -EFAULT;
+ if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
+ goto out;
+
+ /* only enable the requested features for this uffd context */
+ ctx_features = uffd_ctx_features(features);
+ ret = -EINVAL;
+ if (cmpxchg(&ctx->features, 0, ctx_features) != 0)
+ goto err_out;
+
+ ret = 0;
+out:
+ return ret;
+err_out:
+ memset(&uffdio_api, 0, sizeof(uffdio_api));
+ if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
+ ret = -EFAULT;
+ goto out;
+}
+
+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 && !userfaultfd_is_initialized(ctx))
+ 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;
+ case UFFDIO_MOVE:
+ ret = userfaultfd_move(ctx, arg);
+ break;
+ case UFFDIO_WRITEPROTECT:
+ ret = userfaultfd_writeprotect(ctx, arg);
+ break;
+ case UFFDIO_CONTINUE:
+ ret = userfaultfd_continue(ctx, arg);
+ break;
+ case UFFDIO_POISON:
+ ret = userfaultfd_poison(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_iter = userfaultfd_read_iter,
+ .unlocked_ioctl = userfaultfd_ioctl,
+ .compat_ioctl = compat_ptr_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_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock);
+}
+
+static int new_userfaultfd(int flags)
+{
+ struct userfaultfd_ctx *ctx __free(kfree) = NULL;
+
+ VM_WARN_ON_ONCE(!current->mm);
+
+ /* Check the UFFD_* constants for consistency. */
+ BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS);
+
+ if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY))
+ 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->released = false;
+ init_rwsem(&ctx->map_changing_lock);
+ atomic_set(&ctx->mmap_changing, 0);
+ ctx->mm = current->mm;
+
+ FD_PREPARE(fdf, flags & UFFD_SHARED_FCNTL_FLAGS,
+ anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
+ O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS),
+ NULL));
+ if (fdf.err)
+ return fdf.err;
+
+ /* prevent the mm struct to be freed */
+ mmgrab(ctx->mm);
+ fd_prepare_file(fdf)->f_mode |= FMODE_NOWAIT;
+ retain_and_null_ptr(ctx);
+ return fd_publish(fdf);
+}
+
+static inline bool userfaultfd_syscall_allowed(int flags)
+{
+ /* Userspace-only page faults are always allowed */
+ if (flags & UFFD_USER_MODE_ONLY)
+ return true;
+
+ /*
+ * The user is requesting a userfaultfd which can handle kernel faults.
+ * Privileged users are always allowed to do this.
+ */
+ if (capable(CAP_SYS_PTRACE))
+ return true;
+
+ /* Otherwise, access to kernel fault handling is sysctl controlled. */
+ return sysctl_unprivileged_userfaultfd;
+}
+
+SYSCALL_DEFINE1(userfaultfd, int, flags)
+{
+ if (!userfaultfd_syscall_allowed(flags))
+ return -EPERM;
+
+ return new_userfaultfd(flags);
+}
+
+static long userfaultfd_dev_ioctl(struct file *file, unsigned int cmd, unsigned long flags)
+{
+ if (cmd != USERFAULTFD_IOC_NEW)
+ return -EINVAL;
+
+ return new_userfaultfd(flags);
+}
+
+static const struct file_operations userfaultfd_dev_fops = {
+ .unlocked_ioctl = userfaultfd_dev_ioctl,
+ .compat_ioctl = userfaultfd_dev_ioctl,
+ .owner = THIS_MODULE,
+ .llseek = noop_llseek,
+};
+
+static struct miscdevice userfaultfd_misc = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "userfaultfd",
+ .fops = &userfaultfd_dev_fops
+};
+
+static int __init userfaultfd_init(void)
+{
+ int ret;
+
+ ret = misc_register(&userfaultfd_misc);
+ if (ret)
+ return ret;
+
+ userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
+ sizeof(struct userfaultfd_ctx),
+ 0,
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC,
+ init_once_userfaultfd_ctx);
+#ifdef CONFIG_SYSCTL
+ register_sysctl_init("vm", vm_userfaultfd_table);
+#endif
+ return 0;
+}
+__initcall(userfaultfd_init);
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread