linux-kernel - [PATCH 3.2 134/164] unix/caif: sk_socket can disappear when state is unlocked

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Message-ID: <lsq.1438473758.943823962@decadent.org.uk>
Date:	Sun, 02 Aug 2015 01:02:38 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
	"Hannes Frederic Sowa" <hannes@...essinduktion.org>,
	"Mark Salyzyn" <salyzyn@...roid.com>
Subject: [PATCH 3.2 134/164] unix/caif: sk_socket can disappear when state
 is unlocked

3.2.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mark Salyzyn <salyzyn@...roid.com>

[ Upstream commit b48732e4a48d80ed4a14812f0bab09560846514e ]

got a rare NULL pointer dereference in clear_bit

Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
----
v2: switch to sock_flag(sk, SOCK_DEAD) and added net/caif/caif_socket.c
v3: return -ECONNRESET in upstream caller of wait function for SOCK_DEAD
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/caif/caif_socket.c | 8 ++++++++
 net/unix/af_unix.c     | 8 ++++++++
 2 files changed, 16 insertions(+)

--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -366,6 +366,10 @@ static long caif_stream_data_wait(struct
 		release_sock(sk);
 		timeo = schedule_timeout(timeo);
 		lock_sock(sk);
+
+		if (sock_flag(sk, SOCK_DEAD))
+			break;
+
 		clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
 	}
 
@@ -410,6 +414,10 @@ static int caif_stream_recvmsg(struct ki
 		struct sk_buff *skb;
 
 		lock_sock(sk);
+		if (sock_flag(sk, SOCK_DEAD)) {
+			err = -ECONNRESET;
+			goto unlock;
+		}
 		skb = skb_dequeue(&sk->sk_receive_queue);
 		caif_check_flow_release(sk);
 
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1870,6 +1870,10 @@ static long unix_stream_data_wait(struct
 		unix_state_unlock(sk);
 		timeo = schedule_timeout(timeo);
 		unix_state_lock(sk);
+
+		if (sock_flag(sk, SOCK_DEAD))
+			break;
+
 		clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
 	}
 
@@ -1930,6 +1934,10 @@ static int unix_stream_recvmsg(struct ki
 		struct sk_buff *skb;
 
 		unix_state_lock(sk);
+		if (sock_flag(sk, SOCK_DEAD)) {
+			err = -ECONNRESET;
+			goto unlock;
+		}
 		skb = skb_peek(&sk->sk_receive_queue);
 		if (skb == NULL) {
 			unix_sk(sk)->recursion_level = 0;

--
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