CVE-2026-72105: dm-log: fix a bitset_size overflow on 32bit machines

Severity: high (CVSS 7.8 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: 2026-08-15 · updated 2026-10-19
Weakness: CWE-190

Description

In the Linux kernel, the following vulnerability has been resolved: dm-log: fix a bitset_size overflow on 32bit machines Commit c20e36b7631d ("dm log: fix out-of-bounds write due to region_count overflow") made sure that region_count could fit in an unsigned int. But the bitmap memory isn't allocated based on region_count. It uses bitset_size (a size_t variable). The first step of calculating bitset_size is to set it to region_count, rounded up to a multiple of BITS_PER_LONG. If region_size is less than BITS_PER_LONG smaller than UINT_MAX, it will get rounded up to 2^32. On a 32bit architecture, this will make bitset_size wrap around to 0 and fail, despite region_count being valid. Since bitset_size gets divided by 8, it can hold any valid region_count. It just needs a special case to handle the rollover. If it is 0, the value rolled over, and bitset size should be set to the number of bytes needed to hold 2^32 bits.

Affected products

Linux kernel: from 5.10.258 before 5.10.261; from 5.15.209 before 5.15.212; from 6.1.175 before 6.1.178; from 6.6.141 before 6.6.145; from 6.12.91 before 6.12.97; from 6.18.33 before 6.18.40 — fixed in 5.10.261, 5.15.212, 6.1.178, 6.12.97, 6.18.40, 6.6.145

How to fix

Upgrade to a fixed version: Linux kernel 5.10.261, 5.15.212, 6.1.178, 6.12.97. Check the vendor advisory for mitigations.

References

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