From 0dec22a09da1e93126258a1e89812caa80a4b8a0 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 26 May 2023 15:43:42 +0000 Subject: [PATCH] af_packet: do not use READ_ONCE() in packet_bind() [ Upstream commit 6ffc57ea004234d9373c57b204fd10370a69f392 ] A recent patch added READ_ONCE() in packet_bind() and packet_bind_spkt() This is better handled by reading pkt_sk(sk)->num later in packet_do_bind() while appropriate lock is held. READ_ONCE() in writers are often an evidence of something being wrong. Fixes: 822b5a1c17df ("af_packet: Fix data-races of pkt_sk(sk)->num.") Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn Reviewed-by: Jiri Pirko Reviewed-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20230526154342.2533026-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/packet/af_packet.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index c75191b0c82b..6ab9d5b54338 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3193,6 +3193,9 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex, lock_sock(sk); spin_lock(&po->bind_lock); + if (!proto) + proto = po->num; + rcu_read_lock(); if (po->fanout) { @@ -3291,7 +3294,7 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr, memcpy(name, uaddr->sa_data, sizeof(uaddr->sa_data)); name[sizeof(uaddr->sa_data)] = 0; - return packet_do_bind(sk, name, 0, READ_ONCE(pkt_sk(sk)->num)); + return packet_do_bind(sk, name, 0, 0); } static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) @@ -3308,8 +3311,7 @@ static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len if (sll->sll_family != AF_PACKET) return -EINVAL; - return packet_do_bind(sk, NULL, sll->sll_ifindex, - sll->sll_protocol ? : READ_ONCE(pkt_sk(sk)->num)); + return packet_do_bind(sk, NULL, sll->sll_ifindex, sll->sll_protocol); } static struct proto packet_proto = {