[PATCH v3] net/unix: sk_socket can disappear when state is unlocked

[Mark Salyzyn]

got a rare NULL pointer dereference in clear_bit

Signed-off-by: Mark Salyzyn <saly...@android.com>
----
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
---
 net/caif/caif_socket.c | 8 ++++++++
 net/unix/af_unix.c     | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 4ec0c80..112ad78 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -330,6 +330,10 @@ static long caif_stream_data_wait(struct sock *sk, long 
timeo)
                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);
        }
 
@@ -373,6 +377,10 @@ static int caif_stream_recvmsg(struct socket *sock, struct 
msghdr *msg,
                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);
 
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5266ea7..0643059 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1880,6 +1880,10 @@ static long unix_stream_data_wait(struct sock *sk, long 
timeo,
                unix_state_unlock(sk);
                timeo = freezable_schedule_timeout(timeo);
                unix_state_lock(sk);
+
+               if (sock_flag(sk, SOCK_DEAD))
+                       break;
+
                clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
        }
 
@@ -1939,6 +1943,10 @@ static int unix_stream_recvmsg(struct socket *sock, 
struct msghdr *msg,
                struct sk_buff *skb, *last;
 
                unix_state_lock(sk);
+               if (sock_flag(sk, SOCK_DEAD)) {
+                       err = -ECONNRESET;
+                       goto unlock;
+               }
                last = skb = skb_peek(&sk->sk_receive_queue);
 again:
                if (skb == NULL) {
-- 
2.2.0.rc0.207.ga3a616c

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