net: Fix a data-race around sysctl_tstamp_allow_data.

[ Upstream commit d2154b0afa73c0159b2856f875c6b4fe7cf6a95e ]

While reading sysctl_tstamp_allow_data, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its reader.

Fixes: b245be1f4db1 ("net-timestamp: no-payload only sysctl")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5b3559cb1d82794c0fffcb3f6ec5b26fc523208f..bebf58464d6670deb05930defe43bd567427613a 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4772,7 +4772,7 @@ static bool skb_may_tx_timestamp(struct sock *sk, bool tsonly)
 {
        bool ret;
 
-       if (likely(sysctl_tstamp_allow_data || tsonly))
+       if (likely(READ_ONCE(sysctl_tstamp_allow_data) || tsonly))
                return true;
 
        read_lock_bh(&sk->sk_callback_lock);