CVE-2026-31474can: isotp: fix tx.buf use-after-free in isotp_sendmsg()

Official description

In the Linux kernel, the following vulnerability has been resolved: can: isotp: fix tx.buf use-after-free in isotp_sendmsg() isotp_sendmsg() uses only cmpxchg() on so->tx.state to serialize access to so->tx.buf. isotp_release() waits for ISOTP_IDLE via wait_event_interruptible() and then calls kfree(so->tx.buf). If a signal interrupts the wait_event_interruptible() inside close() while tx.state is ISOTP_SENDING, the loop exits early and release proceeds to force ISOTP_SHUTDOWN and continues to kfree(so->tx.buf) while sendmsg may still be reading so->tx.buf for the final CAN frame in isotp_fill_dataframe(). The so->tx.buf can be allocated once when the standard tx.buf length needs to be extended. Move the kfree() of this potentially extended tx.buf to sk_destruct time when either isotp_sendmsg() and isotp_release() are done.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/cb3d6efa78460e6d50bf68806d0db66265709f64
• https://git.kernel.org/stable/c/9649d051e54413049c009638ec1dc23962c884a4
• https://git.kernel.org/stable/c/eec8a1b18a79600bd4419079dc0026c1db72a830
• https://git.kernel.org/stable/c/2e62e7051eca75a7f2e3d52d62ec10d7d7aa358c
• https://git.kernel.org/stable/c/424e95d62110cdbc8fd12b40918f37e408e35a92
• https://access.redhat.com/security/cve/CVE-2026-31474 vdb-entry, x_refsource_REDHAT
• RHBZ#2460646 issue-tracking, x_refsource_REDHAT
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31474.json x_sadp-csaf-vex
• https://access.redhat.com/errata/RHSA-2026:27731 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:27288 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:27789 vendor-advisory, x_refsource_REDHAT