CVE-2026-80710
nicheHeap overflow via integer truncation in Linux kernel s390 DASD (ECKD) driver
The Linux kernel's s390 DASD (ECKD) driver computes a format-check buffer size into a 32-bit int, truncating a 64-bit product of the caller-controlled track count (start_unit/stop_unit) and record counts. For a sufficiently large requested track range, the truncated value makes kzalloc() succeed with an undersized buffer while the subsequent channel-program build still writes the full, untruncated track count, overflowing the heap. A local process with access to the affected DASD device could corrupt adjacent kernel memory, potentially gaining privilege escalation or causing kernel memory disclosure or a crash. Only Linux systems running on IBM Z/LinuxONE (s390) that use ECKD DASD storage are affected; mainstream x86/ARM deployments are not. No public proof-of-concept or in-the-wild exploitation is known (EPSS 0.1%, not in CISA KEV).
What to do: Update the kernel to a build that includes the s390/dasd fix (which computes the buffer size in size_t with check_mul_overflow() and returns -EINVAL on overflow); no fixed version numbers are provided in the data, so track your distribution's kernel updates. As an interim mitigation on s390 systems, restrict local access to DASD device nodes and avoid format-check requests with very large start_unit/stop_unit ranges. x86/ARM and other non-s390 Linux systems do not need action.
| Linux kernel (s390 DASD/ECKD driver, dasd_eckd_check_device_format()) | — |
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
In the Linux kernel, the following vulnerability has been resolved: s390/dasd: Fix undersized format-check buffer fmt_buffer_size in dasd_eckd_check_device_format() is declared as int, even though one of the multiplicands, sizeof(struct eckd_count), is a size_t. 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 fmt_buffer_size variable. For a sufficiently large track range (start_unit/stop_unit 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 check_mul_overflow() 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.
- Vector
- CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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