On 06/10/2025 12:36, David Hildenbrand wrote:
On 03.10.25 17:52, Ryan Roberts wrote:
fsnotify_mmap_perm() requires a byte offset for the file about to be mmap'ed. But it is called from vm_mmap_pgoff(), which has a page offset. Previously the conversion was done incorrectly so let's fix it, being careful not to overflow on 32-bit platforms.
Discovered during code review.
Cc: stable@vger.kernel.org Fixes: 066e053fe208 ("fsnotify: add pre-content hooks on mmap()") Signed-off-by: Ryan Roberts ryan.roberts@arm.com
Applies against today's mm-unstable (aa05a436eca8).
Curious: is there some easy way to write a reproducer? Did you look into that?
I didn't; this was just a drive-by discovery.
It looks like there are some fanotify tests in the filesystems selftests; I guess they could be extended to add a regression test?
But FWIW, I think the kernel is just passing the ofset/length info off to user space and isn't acting on it itself. So there is no kernel vulnerability here.
LGTM, thanks
Acked-by: David Hildenbrand david@redhat.com