CVE-2024-36000

In the Linux kernel, the following vulnerability has been resolved:

mm/hugetlb: fix missing hugetlb_lock for resv uncharge

There is a recent report on UFFDIO_COPY over hugetlb:

https://lore.kernel.org/all/000000000000ee06de0616177560@google.com/

350: lockdep_assert_held(&hugetlb_lock);

Should be an issue in hugetlb but triggered in an userfault context, where it goes into the unlikely path where two threads modifying the resv map together. Mike has a fix in that path for resv uncharge but it looks like the locking criteria was overlooked: hugetlb_cgroup_uncharge_folio_rsvd() will update the cgroup pointer, so it requires to be called with the lock held.

Weakness

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

Affected Software

Extended Description

While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.

Potential Mitigations

References

• https://git.kernel.org/stable/c/4c806333efea1000a2a9620926f560ad2e1ca7cc
• https://git.kernel.org/stable/c/538faabf31e9c53d8c870d114846fda958a0de10
• https://git.kernel.org/stable/c/b76b46902c2d0395488c8412e1116c2486cdfcb2
• https://git.kernel.org/stable/c/f6c5d21db16a0910152ec8aa9d5a7aed72694505
• https://git.kernel.org/stable/c/4c806333efea1000a2a9620926f560ad2e1ca7cc
• https://git.kernel.org/stable/c/538faabf31e9c53d8c870d114846fda958a0de10
• https://git.kernel.org/stable/c/b76b46902c2d0395488c8412e1116c2486cdfcb2
• https://git.kernel.org/stable/c/f6c5d21db16a0910152ec8aa9d5a7aed72694505