CVE-2026-31474

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.