[SRU][N][PATCH 0/1] CVE-2025-37958

[Massimiliano Pellizzer]

https://ubuntu.com/security/CVE-2025-37958

[ Impact ]

mm/huge_memory: fix dereferencing invalid pmd migration entry

When migrating a THP, concurrent access to the PMD migration entry during
a deferred split scan can lead to an invalid address access.
To prevent this invalid access, it is necessary to
check the PMD migration entry and return early.

[ Fix ]

Backport the following fix commit from upstream:
 be6e843fc51a mm/huge_memory: fix dereferencing invalid pmd migration entry

[ Test Plan ]

Compile and boot tested.
Stress tested memory subsystem:
$ sudo stress-ng --class memory --sequential 4 --timeout 30 --metrics-brief
...
stress-ng: info:  [1072] passed: 212: ...
stress-ng: info:  [1072] failed: 0
stress-ng: info:  [1072] metrics untrustworthy: 0
stress-ng: info:  [1072] successful run completed in 26 mins, 34.97 secs


[ Regression Potential ]

The fix modifies THP splitting and deferred-split handling to skip PMD
migration entries. An issue with this patch may cause legitimate PMDs to
be misclassified and skipped, increasing fragmentation and reclaim
latency.

[ Other Info ]

Questing not affected.
Plucky and Jammy fixed through stable updates.

Gavin Guo (1):
  mm/huge_memory: fix dereferencing invalid pmd migration entry

 mm/huge_memory.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

-- 
2.48.1