Executive brief
A vulnerability was identified in the Linux kernel's s390 networking driver (CTCM). This component is responsible for channel-to-channel communications on IBM Z systems. An exploit could lead to a system crash or potentially allow an attacker to execute unauthorized code, impacting the stability and security of the mainframe environment.
Technical details
A double-free vulnerability exists in the s390/ctcm driver within the Linux kernel. The root cause is located in the 'ctcmpc_unpack_skb' function, which conditionally calls 'mpc_rcvd_sweep_req'. Both functions were attempting to free the same 'mpcginfo' structure using 'kfree'. An attacker with adjacent network access could potentially trigger this condition to cause a kernel panic (DoS) or achieve memory corruption. The issue has been resolved by removing the redundant 'kfree' call in 'mpc_rcvd_sweep_req'. Patches are available in various stable kernel branches including 5.4.y, 5.10.y, and 5.15.y.
Affected products
- Linux Linux Kernel 5.4.195 to 5.4.302, 5.10.117 to 5.10.247, 5.15.41 to 5.15.197
Timeline
- 2025-12-04: disclosed
- 2025-12-04: advisory
References
- https://git.kernel.org/stable/c/06f1dd1de0d33dbfbd2e1fc9fc57d8895f730de2
- https://git.kernel.org/stable/c/3b177b2ded563df16f6d5920671ffcfe5915d472
- https://git.kernel.org/stable/c/43096dab8cc60fc39133205fd149a54d3acebea8
- https://git.kernel.org/stable/c/6bf8ccaabce8cebb6cb1f255c93d0acdfe95c17a
- https://git.kernel.org/stable/c/7616e2eee679746d526c7f5befd4eedb995935b5
- https://git.kernel.org/stable/c/7ff76f8dc6b550f8d16487bf3cebc278be720b5c
- https://git.kernel.org/stable/c/b9dbfb1b5699f9f1e4991f96741bdf9047147589