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authorTung Nguyen <tung.q.nguyen@dektech.com.au>2019-02-25 10:57:20 +0700
committerDavid S. Miller <davem@davemloft.net>2019-02-26 14:50:50 -0800
commitbfd07f3dd4f111b884d7922b37eb239280f83d8c (patch)
tree2d591b1836765b0f91ef21a7cd7b8ee0bd056e4b /net/tipc
parentbf48648d650db1146b75b9bd358502431e86cf4f (diff)
downloadlinux-bfd07f3dd4f111b884d7922b37eb239280f83d8c.tar.bz2
tipc: fix race condition causing hung sendto
When sending multicast messages via blocking socket, if sending link is congested (tsk->cong_link_cnt is set to 1), the sending thread will be put into sleeping state. However, tipc_sk_filter_rcv() is called under socket spin lock but tipc_wait_for_cond() is not. So, there is no guarantee that the setting of tsk->cong_link_cnt to 0 in tipc_sk_proto_rcv() in CPU-1 will be perceived by CPU-0. If that is the case, the sending thread in CPU-0 after being waken up, will continue to see tsk->cong_link_cnt as 1 and put the sending thread into sleeping state again. The sending thread will sleep forever. CPU-0 | CPU-1 tipc_wait_for_cond() | { | // condition_ = !tsk->cong_link_cnt | while ((rc_ = !(condition_))) { | ... | release_sock(sk_); | wait_woken(); | | if (!sock_owned_by_user(sk)) | tipc_sk_filter_rcv() | { | ... | tipc_sk_proto_rcv() | { | ... | tsk->cong_link_cnt--; | ... | sk->sk_write_space(sk); | ... | } | ... | } sched_annotate_sleep(); | lock_sock(sk_); | remove_wait_queue(); | } | } | This commit fixes it by adding memory barrier to tipc_sk_proto_rcv() and tipc_wait_for_cond(). Acked-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: Tung Nguyen <tung.q.nguyen@dektech.com.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc')
-rw-r--r--net/tipc/socket.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 684f2125fc6b..70343ac448b1 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -379,11 +379,13 @@ static int tipc_sk_sock_err(struct socket *sock, long *timeout)
#define tipc_wait_for_cond(sock_, timeo_, condition_) \
({ \
+ DEFINE_WAIT_FUNC(wait_, woken_wake_function); \
struct sock *sk_; \
int rc_; \
\
while ((rc_ = !(condition_))) { \
- DEFINE_WAIT_FUNC(wait_, woken_wake_function); \
+ /* coupled with smp_wmb() in tipc_sk_proto_rcv() */ \
+ smp_rmb(); \
sk_ = (sock_)->sk; \
rc_ = tipc_sk_sock_err((sock_), timeo_); \
if (rc_) \
@@ -1983,6 +1985,8 @@ static void tipc_sk_proto_rcv(struct sock *sk,
return;
case SOCK_WAKEUP:
tipc_dest_del(&tsk->cong_links, msg_orignode(hdr), 0);
+ /* coupled with smp_rmb() in tipc_wait_for_cond() */
+ smp_wmb();
tsk->cong_link_cnt--;
wakeup = true;
break;