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mm/hugetlb: make userfaultfd_huge_must_wait() safe to pmd unshare

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We can take the hugetlb walker lock, here taking vma lock directly.

Link: https://lkml.kernel.org/r/20221216155217.2043700-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2022-12-16 10:52:17 -05:00 committed by Andrew Morton
parent fcd48540d1
commit b8da2e4660
1 changed files with 16 additions and 4 deletions
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20
fs/userfaultfd.c
View file

@ -391,7 +391,8 @@ static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags)
*/
vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
{
struct mm_struct *mm = vmf->vma->vm_mm;
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;
@ -418,7 +419,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
*/
mmap_assert_locked(mm);
ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
ctx = vma->vm_userfaultfd_ctx.ctx;
if (!ctx)
goto out;
@ -508,6 +509,15 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
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
@ -522,13 +532,15 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
set_current_state(blocking_state);
spin_unlock_irq(&ctx->fault_pending_wqh.lock);
if (!is_vm_hugetlb_page(vmf->vma))
if (!is_vm_hugetlb_page(vma))
must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
reason);
else
must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma,
must_wait = userfaultfd_huge_must_wait(ctx, vma,
vmf->address,
vmf->flags, reason);
if (is_vm_hugetlb_page(vma))
hugetlb_vma_unlock_read(vma);
mmap_read_unlock(mm);
if (likely(must_wait && !READ_ONCE(ctx->released))) {