linux-kernel - net/unix: sk_socket can disappear when state is unlocked

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Date:	Thu, 21 May 2015 09:25:32 -0700
From:	Mark Salyzyn <salyzyn@...roid.com>
To:	linux-kernel@...r.kernel.org
Cc:	Mark Salyzyn <salyzyn@...roid.com>,
	"David S. Miller" <davem@...emloft.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Ying Xue <ying.xue@...driver.com>,
	Christoph Hellwig <hch@....de>, netdev@...r.kernel.org
Subject: net/unix: sk_socket can disappear when state is unlocked

got a rare NULL pointer dereference in clear_bit

Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
---
 net/unix/af_unix.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5266ea7..37a8925 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1880,6 +1880,11 @@ static long unix_stream_data_wait(struct sock *sk, long timeo,
 		unix_state_unlock(sk);
 		timeo = freezable_schedule_timeout(timeo);
 		unix_state_lock(sk);
+
+		/* sk_socket may have been killed while unlocked */
+		if (!sk->sk_socket)
+			break;
+
 		clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
 	}
 
-- 
2.2.0.rc0.207.ga3a616c

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