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| author | Mike Rapoport <rppt@linux.vnet.ibm.com> | 2018-08-02 15:36:09 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-06 16:18:21 +0200 |
| commit | 9559dd910cfa7e01667949b700989a17d6283df1 (patch) | |
| tree | 9e9f3fa23d79698f2c22ee12faa36c31812ac2a5 | |
| parent | 80755071c18c1cf1155fe533c1d0901f894b43ea (diff) | |
| download | linux-stable-9559dd910cfa7e01667949b700989a17d6283df1.tar.gz linux-stable-9559dd910cfa7e01667949b700989a17d6283df1.tar.bz2 linux-stable-9559dd910cfa7e01667949b700989a17d6283df1.zip | |
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.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 1d85efacfc8e..f4845cdd4926 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -631,8 +631,10 @@ 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); |