CVE-2026-72105

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 isnt 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.

Weakness

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• If possible, choose a language or compiler that performs automatic bounds checking.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
• Use libraries or frameworks that make it easier to handle numbers without unexpected consequences.
• Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++). [REF-106]
• Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.
• Use unsigned integers where possible. This makes it easier to perform validation for integer overflows. When signed integers are required, ensure that the range check includes minimum values as well as maximum values.
• Understand the programming language’s underlying representation and how it interacts with numeric calculation (CWE-681). Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, “not-a-number” calculations, and how the language handles numbers that are too large or too small for its underlying representation. [REF-7]
• Also be careful to account for 32-bit, 64-bit, and other potential differences that may affect the numeric representation.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/92.html

References

• https://git.kernel.org/stable/c/1c3412b584e1fb6c665ff33ba7259253bc0082cb
• https://git.kernel.org/stable/c/4b0de5a3ac1fd42acb0dc1f80ac5747e3287d723
• https://git.kernel.org/stable/c/567602fa72d57169365cbc589e0b8c3be900636d
• https://git.kernel.org/stable/c/79feb87ab2396d49b9b65e4bb815d33cc71cba47
• https://git.kernel.org/stable/c/9743132a41f4d9d0e54c5f2adcb821b04796bab1
• https://git.kernel.org/stable/c/cdc4ddf9db2cb79f4ab86b1a509b7ac21b0b6cf5
• https://git.kernel.org/stable/c/d05e0edfecf5260e6dddd28b2f0cce02bfc6ed7a
• https://git.kernel.org/stable/c/e0b0163a65758ec3a2361ae1cea407898c27f21e