From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Fri, 10 Aug 2007 22:21:17 +0000 (-0700)
Subject: [DCCP]: fix theoretical ccids_{read,write}_lock() race
X-Git-Tag: firefly_0821_release~26778^2~6
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d725fdc8027a4cd961f58d92917fbb91b171abfa;p=firefly-linux-kernel-4.4.55.git

[DCCP]: fix theoretical ccids_{read,write}_lock() race

Make sure that spin_unlock_wait() is properly ordered wrt atomic_inc().

(akpm: can't we convert this code to use rwlocks?)

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/dccp/ccid.c b/net/dccp/ccid.c
index ccbf72c793b6..c45088b5e6fb 100644
--- a/net/dccp/ccid.c
+++ b/net/dccp/ccid.c
@@ -40,6 +40,7 @@ static inline void ccids_write_unlock(void)
 static inline void ccids_read_lock(void)
 {
 	atomic_inc(&ccids_lockct);
+	smp_mb__after_atomic_inc();
 	spin_unlock_wait(&ccids_lock);
 }