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Miller" , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 08/16] net/packet: annotate accesses to po->bind Date: Mon, 21 Jun 2021 13:54:42 -0400 Message-Id: <20210621175450.736067-8-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210621175450.736067-1-sashal@kernel.org> References: <20210621175450.736067-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet [ Upstream commit c7d2ef5dd4b03ed0ee1d13bc0c55f9cf62d49bd6 ] tpacket_snd(), packet_snd(), packet_getname() and packet_seq_show() can read po->num without holding a lock. This means other threads can change po->num at the same time. KCSAN complained about this known fact [1] Add READ_ONCE()/WRITE_ONCE() to address the issue. [1] BUG: KCSAN: data-race in packet_do_bind / packet_sendmsg write to 0xffff888131a0dcc0 of 2 bytes by task 24714 on cpu 0: packet_do_bind+0x3ab/0x7e0 net/packet/af_packet.c:3181 packet_bind+0xc3/0xd0 net/packet/af_packet.c:3255 __sys_bind+0x200/0x290 net/socket.c:1637 __do_sys_bind net/socket.c:1648 [inline] __se_sys_bind net/socket.c:1646 [inline] __x64_sys_bind+0x3d/0x50 net/socket.c:1646 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff888131a0dcc0 of 2 bytes by task 24719 on cpu 1: packet_snd net/packet/af_packet.c:2899 [inline] packet_sendmsg+0x317/0x3570 net/packet/af_packet.c:3040 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg net/socket.c:674 [inline] ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350 ___sys_sendmsg net/socket.c:2404 [inline] __sys_sendmsg+0x1ed/0x270 net/socket.c:2433 __do_sys_sendmsg net/socket.c:2442 [inline] __se_sys_sendmsg net/socket.c:2440 [inline] __x64_sys_sendmsg+0x42/0x50 net/socket.c:2440 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x0000 -> 0x1200 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 24719 Comm: syz-executor.5 Not tainted 5.13.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/packet/af_packet.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 16b745d254fe..42299fa02038 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2656,7 +2656,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) } if (likely(saddr == NULL)) { dev = packet_cached_dev_get(po); - proto = po->num; + proto = READ_ONCE(po->num); } else { err = -EINVAL; if (msg->msg_namelen < sizeof(struct sockaddr_ll)) @@ -2869,7 +2869,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) if (likely(saddr == NULL)) { dev = packet_cached_dev_get(po); - proto = po->num; + proto = READ_ONCE(po->num); } else { err = -EINVAL; if (msg->msg_namelen < sizeof(struct sockaddr_ll)) @@ -3141,7 +3141,7 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex, /* prevents packet_notifier() from calling * register_prot_hook() */ - po->num = 0; + WRITE_ONCE(po->num, 0); __unregister_prot_hook(sk, true); rcu_read_lock(); dev_curr = po->prot_hook.dev; @@ -3151,7 +3151,7 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex, } BUG_ON(po->running); - po->num = proto; + WRITE_ONCE(po->num, proto); po->prot_hook.type = proto; if (unlikely(unlisted)) { @@ -3497,7 +3497,7 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr, sll->sll_family = AF_PACKET; sll->sll_ifindex = po->ifindex; - sll->sll_protocol = po->num; + sll->sll_protocol = READ_ONCE(po->num); sll->sll_pkttype = 0; rcu_read_lock(); dev = dev_get_by_index_rcu(sock_net(sk), po->ifindex); @@ -4391,7 +4391,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, was_running = po->running; num = po->num; if (was_running) { - po->num = 0; + WRITE_ONCE(po->num, 0); __unregister_prot_hook(sk, false); } spin_unlock(&po->bind_lock); @@ -4426,7 +4426,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, spin_lock(&po->bind_lock); if (was_running) { - po->num = num; + WRITE_ONCE(po->num, num); register_prot_hook(sk); } spin_unlock(&po->bind_lock); @@ -4597,7 +4597,7 @@ static int packet_seq_show(struct seq_file *seq, void *v) s, refcount_read(&s->sk_refcnt), s->sk_type, - ntohs(po->num), + ntohs(READ_ONCE(po->num)), po->ifindex, po->running, atomic_read(&s->sk_rmem_alloc), -- 2.30.2