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authorMike Rapoport <rppt@linux.vnet.ibm.com>2018-08-02 15:36:09 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-08-06 16:20:49 +0200
commit0eba9f5d3d4829fe5cc53abe90a73c33f47405af (patch)
treebdd6c6901d49d20ec7ba5cde02e89ece13358fb3
parenta1b5bcffe4a4e6740545fe8ab4a3381da148ce89 (diff)
userfaultfd: remove uffd flags from vma->vm_flags if UFFD_EVENT_FORK fails
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>
-rw-r--r--fs/userfaultfd.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index f6ed92524a03..3eda623e4cb4 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -628,8 +628,10 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
/* 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);