CVE-2025-38364: maple_tree: fix MA_STATE_PREALLOC flag in mas_preallocate()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-07-25 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: maple_tree: fix MA_STATE_PREALLOC flag in mas_preallocate() Temporarily clear the preallocation flag when explicitly requesting allocations. Pre-existing allocations are already counted against the request through mas_node_count_gfp(), but the allocations will not happen if the MA_STATE_PREALLOC flag is set. This flag is meant to avoid re-allocating in bulk allocation mode, and to detect issues with preallocation calculations. The MA_STATE_PREALLOC flag should also always be set on zero allocations so that detection of underflow allocations will print a WARN_ON() during consumption. User visible effect of this flaw is a WARN_ON() followed by a null pointer dereference when subsequent requests for larger number of nodes is ignored, such as the vma merge retry in mmap_region() caused by drivers altering the vma flags (which happens in v6.6, at least)

Affected products

Debian Linux: 11.0
Linux kernel: from 6.1 before 6.1.146; from 6.2 before 6.6.99; from 6.7 before 6.12.36; from 6.13 before 6.15.5; 6.16-rc1, 6.16-rc2, 6.16-rc3 — fixed in 6.1.146, 6.12.36, 6.15.5, 6.6.99

How to fix

Upgrade to a fixed version: Linux kernel 6.1.146, 6.12.36, 6.15.5, 6.6.99. Check the vendor advisory for mitigations.

References

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