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userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails 

The previous fix in commit 384632e67e ("userfaultfd: non-cooperative:
fix fork use after free") corrected the refcounting in case of
UFFD_EVENT_FORK failure for the fork userfault paths.

That still didn't clear the vma->vm_userfaultfd_ctx of the vmas that
were set to point to the aborted new uffd ctx earlier in
dup_userfaultfd.

Link: http://lkml.kernel.org/r/20171223002505.593-2-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2018-01-04 16:18:09 -08:00 committed by Linus Torvalds
parent d09cfbbfa0
commit 0cbb4b4f4c
1 changed files with 18 additions and 2 deletions
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20
fs/userfaultfd.c
View File

@ -570,11 +570,14 @@ out:
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(&ctx->event_wqh.lock);
/*
@ -601,8 +604,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
new = (struct userfaultfd_ctx *)
(unsigned long)
ewq->msg.arg.reserved.reserved1;
userfaultfd_ctx_put(new);
release_new_ctx = new;
}
break;
}
@ -617,6 +619,20 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
__set_current_state(TASK_RUNNING);
spin_unlock(&ctx->event_wqh.lock);
if (release_new_ctx) {
struct vm_area_struct *vma;
struct mm_struct *mm = release_new_ctx->mm;
/* the various vma->vm_userfaultfd_ctx still points to it */
down_write(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next)
if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx)
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
up_write(&mm->mmap_sem);
userfaultfd_ctx_put(release_new_ctx);
}
/*
* ctx may go away after this if the userfault pseudo fd is
* already released.