Messages in this thread | | | Date | Thu, 06 Feb 2020 13:59:24 +0100 (CET) | Subject | Re: [PATCH v3] skbuff: fix a data race in skb_queue_len() | From | David Miller <> |
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From: Qian Cai <cai@lca.pw> Date: Tue, 4 Feb 2020 13:40:29 -0500
> 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 lockless variant of skb_queue_len() and unix_recvq_full() where > READ_ONCE() is on the read while WRITE_ONCE() is on the write similar to > the commit d7d16a89350a ("net: add skb_queue_empty_lockless()"). > > Signed-off-by: Qian Cai <cai@lca.pw>
Applied, thank you.
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