CVE-2026-80710

In the Linux kernel, the following vulnerability has been resolved:

s390/dasd: Fix undersized format-check buffer

fmtbuffersize in dasdeckdcheckdeviceformat() is declared as int, even though one of the multiplicands, sizeof(struct eckdcount), is a sizet. The expression

trkcount * rpt_max * sizeof(struct eckd_count)

is therefore correctly evaluated at 64-bit width, but the result is silently truncated when it is stored back into the 32-bit fmtbuffersize variable. For a sufficiently large track range (startunit/stopunit are caller-controlled) this truncation yields a buffer size far smaller than the number of tracks actually requested. kzalloc() then succeeds with an undersized allocation, while the subsequent channel program build still operates on the untruncated track count and writes past the end of that buffer.

Compute the buffer size with checkmuloverflow() and keep it in a size_t, so that a value that no longer fits results in -EINVAL instead of a silently truncated allocation size.