From: Eric Dumazet edumazet@google.com
[ 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 edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 b62ec43ed54f..6f55942619d4 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2694,7 +2694,7 @@ 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)) @@ -2907,7 +2907,7 @@ 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)) @@ -3177,7 +3177,7 @@ 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; @@ -3187,7 +3187,7 @@ 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)) { @@ -3534,7 +3534,7 @@ 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); @@ -4429,7 +4429,7 @@ 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); @@ -4464,7 +4464,7 @@ 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); @@ -4635,7 +4635,7 @@ 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),