From: Qian Cai <cai@lca.pw>
To: davem@davemloft.net
Cc: kuba@kernel.org, elver@google.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH] skbuff: fix a data race in skb_queue_len()
Date: Mon, 3 Feb 2020 13:56:30 -0500 [thread overview]
Message-ID: <1580756190-3541-1-git-send-email-cai@lca.pw> (raw)
sk_buff.qlen can be accessed concurrently as noticed by KCSAN,
BUG: KCSAN: data-race in __skb_try_recv_from_queue / unix_dgram_sendmsg
read to 0xffff8a1b1d8a81c0 of 4 bytes by task 5371 on cpu 96:
unix_dgram_sendmsg+0x9a9/0xb70 include/linux/skbuff.h:1821
net/unix/af_unix.c:1761
____sys_sendmsg+0x33e/0x370
___sys_sendmsg+0xa6/0xf0
__sys_sendmsg+0x69/0xf0
__x64_sys_sendmsg+0x51/0x70
do_syscall_64+0x91/0xb47
entry_SYSCALL_64_after_hwframe+0x49/0xbe
write to 0xffff8a1b1d8a81c0 of 4 bytes by task 1 on cpu 99:
__skb_try_recv_from_queue+0x327/0x410 include/linux/skbuff.h:2029
__skb_try_recv_datagram+0xbe/0x220
unix_dgram_recvmsg+0xee/0x850
____sys_recvmsg+0x1fb/0x210
___sys_recvmsg+0xa2/0xf0
__sys_recvmsg+0x66/0xf0
__x64_sys_recvmsg+0x51/0x70
do_syscall_64+0x91/0xb47
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Since only the read is operating as lockless, it could introduce a logic
bug in unix_recvq_full() due to the load tearing. Fix it by adding
a READ_ONCE() there.
Signed-off-by: Qian Cai <cai@lca.pw>
---
include/linux/skbuff.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 3d13a4b717e9..4b5157164f3e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1818,7 +1818,7 @@ static inline struct sk_buff *skb_peek_tail(const struct sk_buff_head *list_)
*/
static inline __u32 skb_queue_len(const struct sk_buff_head *list_)
{
- return list_->qlen;
+ return READ_ONCE(list_->qlen);
}
/**
--
1.8.3.1
next reply other threads:[~2020-02-03 19:02 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-03 18:56 Qian Cai [this message]
2020-02-03 19:41 ` [PATCH] skbuff: fix a data race in skb_queue_len() Eric Dumazet
2020-02-03 20:19 ` Qian Cai
2020-02-03 20:28 ` Eric Dumazet
2020-02-03 22:34 ` Qian Cai
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