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

Official 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 packages & fixed versions

Affected products (as reported)

References

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