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| author | Qian Cai <cai@lca.pw> | 2020-02-04 21:40:29 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-02-06 15:59:10 +0300 |
| commit | 86b18aaa2b5b5bb48e609cd591b3d2d0fdbe0442 (patch) | |
| tree | 39d9ae29d9d944e6a14ed4ddc323b145f1b6b9c0 /include/linux/skbuff.h | |
| parent | c35947b8ff8acca33134ee39c31708233765c31a (diff) | |
| download | linux-86b18aaa2b5b5bb48e609cd591b3d2d0fdbe0442.tar.xz | |
skbuff: fix a data race in skb_queue_len()
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/skbuff.h')
| -rw-r--r-- | include/linux/skbuff.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 3d13a4b717e9..ca8806b69388 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1822,6 +1822,18 @@ static inline __u32 skb_queue_len(const struct sk_buff_head *list_) } /** + * skb_queue_len_lockless - get queue length + * @list_: list to measure + * + * Return the length of an &sk_buff queue. + * This variant can be used in lockless contexts. + */ +static inline __u32 skb_queue_len_lockless(const struct sk_buff_head *list_) +{ + return READ_ONCE(list_->qlen); +} + +/** * __skb_queue_head_init - initialize non-spinlock portions of sk_buff_head * @list: queue to initialize * @@ -2026,7 +2038,7 @@ static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list) { struct sk_buff *next, *prev; - list->qlen--; + WRITE_ONCE(list->qlen, list->qlen - 1); next = skb->next; prev = skb->prev; skb->next = skb->prev = NULL; |