mm/hugetlb: unshare page tables during VMA split, not before
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 5.10.239, 5.15.186, 6.1.142, 6.6.95, 6.12.35, and 1 more
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: total
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: unshare page tables during VMA split, not before Currently, __split_vma() triggers hugetlb page table unsharing through vm_ops->may_split(). This happens before the VMA lock and rmap locks are taken - which is too early, it allows racing VMA-locked page faults in our process and racing rmap walks from other processes to cause page tables to be shared again before we actually perform the split. Fix it by explicitly calling into the hugetlb unshare logic from __split_vma() in the same place where THP splitting also happens. At that point, both the VMA and the rmap(s) are write-locked. An annoying detail is that we can now call into the helper hugetlb_unshare_pmds() from two different locking contexts: 1. from hugetlb_split(), holding: • mmap lock (exclusively) • VMA lock • file rmap lock (exclusively) 2. hugetlb_unshare_all_pmds(), which I think is designed to be able to call us with only the mmap lock held (in shared mode), but currently only runs while holding mmap lock (exclusively) and VMA lock Backporting note: This commit fixes a racy protection that was introduced in commit b30c14cd6102 ("hugetlb: unshare some PMDs when splitting VMAs"); that commit claimed to fix an issue introduced in 5.13, but it should actually also go all the way back. [jannh@google.com: v2]
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- Linux Linux
From 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa · fixed in e8847d18cd9fff1edbb45e963d9141273c3b539c; From 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa · fixed in 366298f2b04d2bf1f2f2b7078405bdf9df9bd5d0; From 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa · fixed in 2511ac64bc1617ca716d3ba8464e481a647c1902; From 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa · fixed in af6cfcd0efb7f051af221c418ec8b37a10211947; From 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa · fixed in 9cf5b2a3b72c23fb7b84736d5d19ee6ea718762b; From 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa · fixed in 8a21d5584826f4880f45bbf8f72375f4e6c0ff2a; From 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa · fixed in 081056dc00a27bccb55ccc3c6f230a3d5fd3f7e0
- Linux Linux
2.6.20
- KernelLinux
From 2.6.20 · fixed in 5.10.239; From 5.11.0 · fixed in 5.15.186; From 5.16.0 · fixed in 6.1.142; From 6.2.0 · fixed in 6.6.95; From 6.7.0 · fixed in 6.12.35; From 6.13.0 · fixed in 6.15.4
References 8
git.kernel.org
- stable/c/e8847d18cd9fff1edbb45e963d9141273c3b539c
- stable/c/366298f2b04d2bf1f2f2b7078405bdf9df9bd5d0
- stable/c/2511ac64bc1617ca716d3ba8464e481a647c1902
- stable/c/af6cfcd0efb7f051af221c418ec8b37a10211947
- stable/c/9cf5b2a3b72c23fb7b84736d5d19ee6ea718762b
- stable/c/8a21d5584826f4880f45bbf8f72375f4e6c0ff2a
- stable/c/081056dc00a27bccb55ccc3c6f230a3d5fd3f7e0