CVE-2025-37760 Information

Description

In the Linux kernel the following vulnerability has been resolved:

mm/vma: add give_up_on_oom option on modify/merge use in uffd release

Currently if a VMA merge fails due to an OOM condition arising on commit merge or a failure to duplicate anon_vma’s we report this so the caller can handle it.

However there are cases where the caller is only ostensibly trying a merge and doesn’t mind if it fails due to this condition.

Since we do not want to introduce an implicit assumption that we only actually modify VMAs after OOM conditions might arise add a ‘give up on oom’ option and make an explicit contract that should this flag be set we absolutely will not modify any VMAs should OOM arise and just bail out.

Since it’d be very unusual for a user to try to vma_modify() with this flag set but be specifying a range within a VMA which ends up being split (which can fail due to rlimit issues not only OOM) we add a debug warning for this condition.

The motivating reason for this is uffd release - syzkaller (and Pedro Falcato’s VERY astute analysis) found a way in which an injected fault on allocation triggering an OOM condition on commit merge would result in uffd code becoming confused and treating an error value as if it were a VMA pointer.

To avoid this we make use of this new VMG flag to ensure that this never occurs utilising the fact that should we be clearing entire VMAs we do not wish an OOM event to be reported to us.

Many thanks to Pedro Falcato for his excellent analysis and Jann Horn for his insightful and intelligent analysis of the situation both of whom were instrumental in this fix.

Reference

https://git.kernel.org/stable/c/41e6ddcaa0f18dda4c3fadf22533775a30d6f72f https://git.kernel.org/stable/c/b906c1ad25adce6ff35be19b65a1aa7d960fe1d7 https://git.kernel.org/stable/c/c103a75c61648203d731e3b97a6fbeea4003cb15