userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails
The previous fix in commit 384632e6 ("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.comSigned-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>
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