Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.17 23/31] userfaultfd: remove uffd flags from vma->vm_flags if UFFD_EVENT_FORK fails | Date | Sat, 4 Aug 2018 11:00:58 +0200 |
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4.17-stable review patch. If anyone has any objections, please let me know.
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From: Mike Rapoport <rppt@linux.vnet.ibm.com>
commit 31e810aa1033a7db50a2746cd34a2432237f6420 upstream.
The fix in commit 0cbb4b4f4c44 ("userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails") cleared the vma->vm_userfaultfd_ctx but kept userfaultfd flags in vma->vm_flags that were copied from the parent process VMA.
As the result, there is an inconsistency between the values of vma->vm_userfaultfd_ctx.ctx and vma->vm_flags which triggers BUG_ON in userfaultfd_release().
Clearing the uffd flags from vma->vm_flags in case of UFFD_EVENT_FORK failure resolves the issue.
Link: http://lkml.kernel.org/r/1532931975-25473-1-git-send-email-rppt@linux.vnet.ibm.com Fixes: 0cbb4b4f4c44 ("userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails") Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Reported-by: syzbot+121be635a7a35ddb7dcb@syzkaller.appspotmail.com Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Eric Biggers <ebiggers3@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/userfaultfd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -631,8 +631,10 @@ static void userfaultfd_event_wait_compl /* 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) + if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; + vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); + } up_write(&mm->mmap_sem); userfaultfd_ctx_put(release_new_ctx);
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