From b7a9bb084483b6a6f91fc1f4e0ad0fbafaeeac09 Mon Sep 17 00:00:00 2001 From: Quang Le Date: Fri, 1 Aug 2025 13:54:16 -0400 Subject: [PATCH] UPSTREAM: net/packet: fix a race in packet_set_ring() and packet_notifier() commit 01d3c8417b9c1b884a8a981a3b886da556512f36 upstream. 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. Bug: 438674212 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Quang Le Signed-off-by: Willem de Bruijn Link: https://patch.msgid.link/20250801175423.2970334-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman (cherry picked from commit f2e8fcfd2b1bc754920108b7f2cd75082c5a18df) Signed-off-by: Lee Jones Change-Id: Ibcc94a6f951a94a6b1a82ebb199b355a1c39a5e1 --- 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 51138bd5aa12..a8a1292d6d9f 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -4503,10 +4503,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, spin_lock(&po->bind_lock); was_running = po->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(); @@ -4538,10 +4538,10 @@ 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 */