x86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF
- 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- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean?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 6.18.53, 7.2.7
- 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
Summary
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF x86 implements page attribute modification using its Change Page Attributes (CPA) mechanism. This tracks properties of ranges such as cache mode through x86 page attributes, and as part of that logic manipulates kernel page tables. Since commit: 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") ranges of kernel page table entries can be collapsed into huge page table entries as part of this logic. As part of this collapse, it frees the page tables which the collapsed entries previously pointed to, and it does so without any relevant locks being held to preclude concurrent kernel page table walkers. The only way this code can be reached is if CPA_COLLAPSE is specified, and this is only set in set_memory_rox() via: set_memory_rox() -> change_page_attr_set_clr() -> cpa_flush() -> cpa_collapse_large_pages() Notable users of this are execmem and BPF when manipulating executable mappings. However, this is problematic for ptdump as it walks ranges it does not own and thus runs the risk of a use-after-free on page tables freed underneath it. In addition, concurrent CPA collapse operations are possible which can also cause races. Resolve the issue by acquiring the mmap write lock on init_mm across the whole operation. It is safe to acquire a sleeping lock as all the callers invoke set_memory_rox() from process context and in any case, change_page_attr_set_clr() calls vm_unmap_alias() which ultimately takes a mutex, disallowing atomic context here.
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 · fixed in 35820cf8dd521f5a651e221483015b0586794516; From 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 · fixed in 93b98882198b15bd482da1fe8e84b05c7c3b3d83; From 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 · fixed in a1c7570cedd03372812a5b693732880867babbca
- Linux Linux
6.15
- KernelLinux
From 6.15.0 · fixed in 6.18.53; From 6.19.0 · fixed in 7.2.7