From: Quang Le quanglex97@gmail.com

When packet_set_ring() releases po->bind_lock, another thread can run packet_notifier() and process an NETDEV_UP event.

This race and the fix are both similar to that of commit 15fe076edea7 ("net/packet: fix a race in packet_bind() and packet_notifier()").

There too the packet_notifier NETDEV_UP event managed to run while a po->bind_lock critical section had to be temporarily released. And the fix was similarly to temporarily set po->num to zero to keep the socket unhooked until the lock is retaken.

The po->bind_lock in packet_set_ring and packet_notifier precede the introduction of git history.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Quang Le quanglex97@gmail.com Signed-off-by: Willem de Bruijn willemb@google.com

---

v1->v2: - fix author attribution (From: at the top)

v1: https://lore.kernel.org/netdev/20250731175132.2592130-1-willemdebruijn.kerne... --- net/packet/af_packet.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index bc438d0d96a7..a7017d7f0927 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -4573,10 +4573,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, spin_lock(&po->bind_lock); was_running = packet_sock_flag(po, PACKET_SOCK_RUNNING); num = po->num; - if (was_running) { - WRITE_ONCE(po->num, 0); + WRITE_ONCE(po->num, 0); + if (was_running) __unregister_prot_hook(sk, false); - } + spin_unlock(&po->bind_lock);

synchronize_net(); @@ -4608,10 +4608,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, mutex_unlock(&po->pg_vec_lock);

spin_lock(&po->bind_lock); - if (was_running) { - WRITE_ONCE(po->num, num); + WRITE_ONCE(po->num, num); + if (was_running) register_prot_hook(sk); - } + spin_unlock(&po->bind_lock); if (pg_vec && (po->tp_version > TPACKET_V2)) { /* Because we don't support block-based V3 on tx-ring */