After calling rose_neigh_put() in rose_state1_machine() through rose_state5_machine(), rose->neighbour was left pointing at the potentially freed neighbour structure. A subsequent timer expiry or concurrent teardown path could dereference the stale pointer, causing a use-after-free. Set rose->neighbour to NULL immediately after each rose_neigh_put() call in the state machine functions. Fixes: d860d1faa6b2 ("net: rose: convert 'use' field to refcount_t") Tested-by: Bernard Pidoux Signed-off-by: Bernard Pidoux --- net/rose/rose_in.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/rose/rose_in.c b/net/rose/rose_in.c index 0276b393f0e5..622527f1354f 100644 --- a/net/rose/rose_in.c +++ b/net/rose/rose_in.c @@ -57,6 +57,7 @@ static int rose_state1_machine(struct sock *sk, struct sk_buff *skb, int framety rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION); rose_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]); rose_neigh_put(rose->neighbour); + rose->neighbour = NULL; break; default: @@ -80,11 +81,13 @@ static int rose_state2_machine(struct sock *sk, struct sk_buff *skb, int framety rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION); rose_disconnect(sk, 0, skb->data[3], skb->data[4]); rose_neigh_put(rose->neighbour); + rose->neighbour = NULL; break; case ROSE_CLEAR_CONFIRMATION: rose_disconnect(sk, 0, -1, -1); rose_neigh_put(rose->neighbour); + rose->neighbour = NULL; break; default: @@ -122,6 +125,7 @@ static int rose_state3_machine(struct sock *sk, struct sk_buff *skb, int framety rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION); rose_disconnect(sk, 0, skb->data[3], skb->data[4]); rose_neigh_put(rose->neighbour); + rose->neighbour = NULL; break; case ROSE_RR: @@ -235,6 +239,7 @@ static int rose_state4_machine(struct sock *sk, struct sk_buff *skb, int framety rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION); rose_disconnect(sk, 0, skb->data[3], skb->data[4]); rose_neigh_put(rose->neighbour); + rose->neighbour = NULL; break; default: @@ -255,6 +260,7 @@ static int rose_state5_machine(struct sock *sk, struct sk_buff *skb, int framety rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION); rose_disconnect(sk, 0, skb->data[3], skb->data[4]); rose_neigh_put(rose_sk(sk)->neighbour); + rose_sk(sk)->neighbour = NULL; } return 0; -- 2.51.0