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* [PATCH net 0/2] net/packet: annotate data races
@ 2021-06-16 13:42 Eric Dumazet
  2021-06-16 13:42 ` [PATCH net 1/2] net/packet: annotate accesses to po->bind Eric Dumazet
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Eric Dumazet @ 2021-06-16 13:42 UTC (permalink / raw)
  To: David S . Miller, Jakub Kicinski; +Cc: netdev, Eric Dumazet, Eric Dumazet

From: Eric Dumazet <edumazet@google.com>

KCSAN sent two reports about data races in af_packet.
Nothing serious, but worth fixing.

Eric Dumazet (2):
  net/packet: annotate accesses to po->bind
  net/packet: annotate accesses to po->ifindex

 net/packet/af_packet.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

-- 
2.32.0.272.g935e593368-goog


^ permalink raw reply	[flat|nested] 4+ messages in thread
* [PATCH net 1/2] net/packet: annotate accesses to po->bind
  2021-06-16 13:42 [PATCH net 0/2] net/packet: annotate data races Eric Dumazet
@ 2021-06-16 13:42 ` Eric Dumazet
  2021-06-16 13:42 ` [PATCH net 2/2] net/packet: annotate accesses to po->ifindex Eric Dumazet
  2021-06-16 19:50 ` [PATCH net 0/2] net/packet: annotate data races patchwork-bot+netdevbpf
  2 siblings, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2021-06-16 13:42 UTC (permalink / raw)
  To: David S . Miller, Jakub Kicinski
  Cc: netdev, Eric Dumazet, Eric Dumazet, syzbot

From: Eric Dumazet <edumazet@google.com>

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>
---
 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 74e6e45a8e8435a556ce813c410a1f4146dd05b6..e91a36bdd1abaf18a679b914ae0d722d42c9369b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2683,7 +2683,7 @@ 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))
@@ -2896,7 +2896,7 @@ 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))
@@ -3171,7 +3171,7 @@ 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;
@@ -3181,7 +3181,7 @@ 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)) {
@@ -3526,7 +3526,7 @@ 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);
@@ -4414,7 +4414,7 @@ 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);
@@ -4449,7 +4449,7 @@ 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);
@@ -4619,7 +4619,7 @@ 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),
-- 
2.32.0.272.g935e593368-goog


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [PATCH net 2/2] net/packet: annotate accesses to po->ifindex
  2021-06-16 13:42 [PATCH net 0/2] net/packet: annotate data races Eric Dumazet
  2021-06-16 13:42 ` [PATCH net 1/2] net/packet: annotate accesses to po->bind Eric Dumazet
@ 2021-06-16 13:42 ` Eric Dumazet
  2021-06-16 19:50 ` [PATCH net 0/2] net/packet: annotate data races patchwork-bot+netdevbpf
  2 siblings, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2021-06-16 13:42 UTC (permalink / raw)
  To: David S . Miller, Jakub Kicinski
  Cc: netdev, Eric Dumazet, Eric Dumazet, syzbot

From: Eric Dumazet <edumazet@google.com>

Like prior patch, we need to annotate lockless accesses to po->ifindex
For instance, packet_getname() is reading po->ifindex (twice) while
another thread is able to change po->ifindex.

KCSAN reported:

BUG: KCSAN: data-race in packet_do_bind / packet_getname

write to 0xffff888143ce3cbc of 4 bytes by task 25573 on cpu 1:
 packet_do_bind+0x420/0x7e0 net/packet/af_packet.c:3191
 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 0xffff888143ce3cbc of 4 bytes by task 25578 on cpu 0:
 packet_getname+0x5b/0x1a0 net/packet/af_packet.c:3525
 __sys_getsockname+0x10e/0x1a0 net/socket.c:1887
 __do_sys_getsockname net/socket.c:1902 [inline]
 __se_sys_getsockname net/socket.c:1899 [inline]
 __x64_sys_getsockname+0x3e/0x50 net/socket.c:1899
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25578 Comm: syz-executor.5 Not tainted 5.13.0-rc6-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>
---
 net/packet/af_packet.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e91a36bdd1abaf18a679b914ae0d722d42c9369b..330ba68828e7dbabf4d4d6b76e7cb664253c432e 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3187,11 +3187,11 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
 		if (unlikely(unlisted)) {
 			dev_put(dev);
 			po->prot_hook.dev = NULL;
-			po->ifindex = -1;
+			WRITE_ONCE(po->ifindex, -1);
 			packet_cached_dev_reset(po);
 		} else {
 			po->prot_hook.dev = dev;
-			po->ifindex = dev ? dev->ifindex : 0;
+			WRITE_ONCE(po->ifindex, dev ? dev->ifindex : 0);
 			packet_cached_dev_assign(po, dev);
 		}
 	}
@@ -3505,7 +3505,7 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
 	uaddr->sa_family = AF_PACKET;
 	memset(uaddr->sa_data, 0, sizeof(uaddr->sa_data));
 	rcu_read_lock();
-	dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
+	dev = dev_get_by_index_rcu(sock_net(sk), READ_ONCE(pkt_sk(sk)->ifindex));
 	if (dev)
 		strlcpy(uaddr->sa_data, dev->name, sizeof(uaddr->sa_data));
 	rcu_read_unlock();
@@ -3520,16 +3520,18 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr,
 	struct sock *sk = sock->sk;
 	struct packet_sock *po = pkt_sk(sk);
 	DECLARE_SOCKADDR(struct sockaddr_ll *, sll, uaddr);
+	int ifindex;
 
 	if (peer)
 		return -EOPNOTSUPP;
 
+	ifindex = READ_ONCE(po->ifindex);
 	sll->sll_family = AF_PACKET;
-	sll->sll_ifindex = po->ifindex;
+	sll->sll_ifindex = ifindex;
 	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);
+	dev = dev_get_by_index_rcu(sock_net(sk), ifindex);
 	if (dev) {
 		sll->sll_hatype = dev->type;
 		sll->sll_halen = dev->addr_len;
@@ -4108,7 +4110,7 @@ static int packet_notifier(struct notifier_block *this,
 				}
 				if (msg == NETDEV_UNREGISTER) {
 					packet_cached_dev_reset(po);
-					po->ifindex = -1;
+					WRITE_ONCE(po->ifindex, -1);
 					if (po->prot_hook.dev)
 						dev_put(po->prot_hook.dev);
 					po->prot_hook.dev = NULL;
@@ -4620,7 +4622,7 @@ static int packet_seq_show(struct seq_file *seq, void *v)
 			   refcount_read(&s->sk_refcnt),
 			   s->sk_type,
 			   ntohs(READ_ONCE(po->num)),
-			   po->ifindex,
+			   READ_ONCE(po->ifindex),
 			   po->running,
 			   atomic_read(&s->sk_rmem_alloc),
 			   from_kuid_munged(seq_user_ns(seq), sock_i_uid(s)),
-- 
2.32.0.272.g935e593368-goog


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH net 0/2] net/packet: annotate data races
  2021-06-16 13:42 [PATCH net 0/2] net/packet: annotate data races Eric Dumazet
  2021-06-16 13:42 ` [PATCH net 1/2] net/packet: annotate accesses to po->bind Eric Dumazet
  2021-06-16 13:42 ` [PATCH net 2/2] net/packet: annotate accesses to po->ifindex Eric Dumazet
@ 2021-06-16 19:50 ` patchwork-bot+netdevbpf
  2 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-06-16 19:50 UTC (permalink / raw)
  To: Eric Dumazet; +Cc: davem, kuba, netdev, edumazet

Hello:

This series was applied to netdev/net.git (refs/heads/master):

On Wed, 16 Jun 2021 06:42:00 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> KCSAN sent two reports about data races in af_packet.
> Nothing serious, but worth fixing.
> 
> Eric Dumazet (2):
>   net/packet: annotate accesses to po->bind
>   net/packet: annotate accesses to po->ifindex
> 
> [...]

Here is the summary with links:
  - [net,1/2] net/packet: annotate accesses to po->bind
    https://git.kernel.org/netdev/net/c/c7d2ef5dd4b0
  - [net,2/2] net/packet: annotate accesses to po->ifindex
    https://git.kernel.org/netdev/net/c/e032f7c9c7ce

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-06-16 19:50 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-06-16 13:42 [PATCH net 0/2] net/packet: annotate data races Eric Dumazet
2021-06-16 13:42 ` [PATCH net 1/2] net/packet: annotate accesses to po->bind Eric Dumazet
2021-06-16 13:42 ` [PATCH net 2/2] net/packet: annotate accesses to po->ifindex Eric Dumazet
2021-06-16 19:50 ` [PATCH net 0/2] net/packet: annotate data races patchwork-bot+netdevbpf

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