can: isotp: fix timer drain order, wakeup handling and tx_gen ordering

Summary

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.

Timeline

1. Sep 4, 2026, 5:11 PM UTCCVE published

Affected versions

• Linux Linux

  Version range not reported

• Linux Linux

  From 5.10.265 · fixed in 5.10.267; From 5.15.216 · fixed in 5.15.218; From 6.1.183 · fixed in 6.1.185; From 6.6.148 · fixed in 6.6.151; From 6.12.101 · fixed in 6.12.103; From 6.18.40 · fixed in 6.18.44; From 7.1.5 · fixed in 7.1.8

References 8