Merge v6.18.37linux-rolling-lts

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/net/rose.h b/include/net/rose.h
index 2b5491bbf39a..95d1f9c582dc 100644
--- a/include/net/rose.h
+++ b/include/net/rose.h
@@ -160,6 +160,18 @@ static inline void rose_neigh_hold(struct rose_neigh *rose_neigh)
 static inline void rose_neigh_put(struct rose_neigh *rose_neigh)
 {
 	if (refcount_dec_and_test(&rose_neigh->use)) {
+		/* We are dropping the last reference, so we are about to free the
+		 * neighbour.  Its timers may still be armed -- t0timer in particular
+		 * re-arms itself in rose_t0timer_expiry().  rose_remove_neigh()
+		 * cancels them before its own put, but callers that drop the final
+		 * reference without first calling rose_remove_neigh() (the socket
+		 * heartbeat reaping path) would otherwise kfree() a neighbour with a
+		 * live timer -> use-after-free.  timer_delete_sync() (not the async
+		 * variant) is required: it waits out a concurrently running handler
+		 * and loops until the self-rearming timer stays stopped.
+		 */
+		timer_delete_sync(&rose_neigh->ftimer);
+		timer_delete_sync(&rose_neigh->t0timer);
 		if (rose_neigh->ax25)
 			ax25_cb_put(rose_neigh->ax25);
 		kfree(rose_neigh->digipeat);