CVE-2026-80889can: isotp: fix timer drain order, wakeup handling and tx_gen ordering

Official description

In the Linux kernel, the following vulnerability has been resolved: can: isotp: fix timer drain order, wakeup handling and tx_gen ordering This patch is a follow-up to commit cf070fe33bfb ("can: isotp: serialize TX state transitions under so->rx_lock") which addresses following sashiko-bot findings: - isotp_sendmsg(): drain so->txfrtimer first so a stale callback can't re-arm echotimer after the claim - isotp_release(): wake so->wait after forcing ISOTP_SHUTDOWN so a sleeping sendmsg() claim isn't stranded - isotp_sendmsg(): have both wait_event_interruptible() calls in isotp_sendmsg() also wake on ISOTP_SHUTDOWN and do not return claim to IDLE to avoid corrupting a concurrent isotp_release() process. - isotp_sendmsg(): handle potential claim of a new transfer when the wait_event_interruptible() call returns in CAN_ISOTP_WAIT_TX_DONE mode. Don't touch timers and states of the new transfer if a new thread incremented so->tx_gen before getting the lock at err_event_drop. - isotp_sendmsg(): handle a stuck can_send() and omit timer and state changes if a new transfer was claimed. wait_tx_done() returns the error recorded in so->tx_result[], tagged with the caller's own generation. - isotp_tx_timeout(): on a claimed timeout, record the ECOMM error for the timed-out transfer's own generation in so->tx_result[]; sk->sk_err is raised unconditionally, same as every other error path here. - isotp_tx_gen_done()/isotp_tx_timeout(): always read tx.state (acquire) before tx_gen - the reverse order let a weakly ordered CPU pair a fresh tx.state with a stale tx_gen/tx_result slot. - isotp_sendmsg(): wait_tx_done: drain sk_err via sock_error() once we have read the result from so->tx_result[], so an already-reported error doesn't stay latched for a later poll()/SO_ERROR. Also align the remaining lock-free so->tx.state/rx.state/cfecho accesses and use skb->hash as unique loopback echo frame indicator.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/8acab9fc66d6f426c36968c91a979f70784945a7
• https://git.kernel.org/stable/c/af7e25c649ed68cbad07f8185af0f31b892cbf29
• https://git.kernel.org/stable/c/2753722612d8824d3910096f93059f669009b0f0
• https://git.kernel.org/stable/c/bf5c4a8b24acb12739ebb9aea5510b007e4f5239
• https://git.kernel.org/stable/c/deca7746b57d982cd4f0301f4443f56780c4a048
• https://git.kernel.org/stable/c/10be509fa8fd95d1e47d40d1f68b0b26dfe9d572
• https://git.kernel.org/stable/c/35c62ac98d06669aa3f0f38b7829eaca929a611e
• https://git.kernel.org/stable/c/050f010f920da17c1044a4f174766ad553e770b6