In rose_timer_expiry(), the ROSE_STATE_2 branch calls rose_neigh_put(rose->neighbour) without first checking whether the pointer is NULL. After commit 5de7665e0a07 ("net: rose: fix timer races against user threads") the timer is re-armed when the socket is owned by a user thread; between the re-arm and the next firing, a device-down event or concurrent teardown via rose_kill_by_device() can set rose->neighbour to NULL, leading to a NULL-pointer dereference inside rose_neigh_put(). Add a NULL check before the put and clear the pointer afterwards. Fixes: 5de7665e0a07 ("net: rose: fix timer races against user threads") Tested-by: Bernard Pidoux Signed-off-by: Bernard Pidoux --- net/rose/rose_timer.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/rose/rose_timer.c b/net/rose/rose_timer.c index bb60a1654d61..d997d24ab081 100644 --- a/net/rose/rose_timer.c +++ b/net/rose/rose_timer.c @@ -180,7 +180,10 @@ static void rose_timer_expiry(struct timer_list *t) break; case ROSE_STATE_2: /* T3 */ - rose_neigh_put(rose->neighbour); + if (rose->neighbour) { + rose_neigh_put(rose->neighbour); + rose->neighbour = NULL; + } rose_disconnect(sk, ETIMEDOUT, -1, -1); break; -- 2.51.0