diff options
| author | Nadav Amit | 2021-10-18 15:15:25 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2021-10-18 20:22:02 -1000 |
| commit | cb185d5f1ebf900f4ae3bf84cee212e6dd035aca (patch) | |
| tree | 1156aa57eb9c1c0c0c52a72ddb33fa91e827584f | |
| parent | 8913970c19915bbe773d97d42989cd85b7fdc098 (diff) | |
userfaultfd: fix a race between writeprotect and exit_mmap()
A race is possible when a process exits, its VMAs are removed by
exit_mmap() and at the same time userfaultfd_writeprotect() is called.
The race was detected by KASAN on a development kernel, but it appears
to be possible on vanilla kernels as well.
Use mmget_not_zero() to prevent the race as done in other userfaultfd
operations.
Link: https://lkml.kernel.org/r/20210921200247.25749-1-namit@vmware.com
Fixes: 63b2d4174c4ad ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl")
Signed-off-by: Nadav Amit <namit@vmware.com>
Tested-by: Li Wang <liwang@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/userfaultfd.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 003f0d31743e..22bf14ab2d16 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1827,9 +1827,15 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, if (mode_wp && mode_dontwake) return -EINVAL; - ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, - uffdio_wp.range.len, mode_wp, - &ctx->mmap_changing); + if (mmget_not_zero(ctx->mm)) { + ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, + uffdio_wp.range.len, mode_wp, + &ctx->mmap_changing); + mmput(ctx->mm); + } else { + return -ESRCH; + } + if (ret) return ret; |