af_unix: Avoid socket->sk NULL OOPS in stream connect security hooks.

unix_release() can asynchornously set socket->sk to NULL, and
it does so without holding the unix_state_lock() on "other"
during stream connects.

However, the reverse mapping, sk->sk_socket, is only transitioned
to NULL under the unix_state_lock().

Therefore make the security hooks follow the reverse mapping instead
of the forward mapping.

Reported-by: Jeremy Fitzhardinge <jeremy@goop.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 8 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index fd4d55fb884..d47a4c24b3e 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -796,8 +796,9 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  * @unix_stream_connect:
  *	Check permissions before establishing a Unix domain stream connection
  *	between @sock and @other.
- *	@sock contains the socket structure.
- *	@other contains the peer socket structure.
+ *	@sock contains the sock structure.
+ *	@other contains the peer sock structure.
+ *	@newsk contains the new sock structure.
  *	Return 0 if permission is granted.
  * @unix_may_send:
  *	Check permissions before connecting or sending datagrams from @sock to
@@ -1568,8 +1569,7 @@ struct security_operations {
 	int (*inode_getsecctx)(struct inode *inode, void **ctx, u32 *ctxlen);
 
 #ifdef CONFIG_SECURITY_NETWORK
-	int (*unix_stream_connect) (struct socket *sock,
-				    struct socket *other, struct sock *newsk);
+	int (*unix_stream_connect) (struct sock *sock, struct sock *other, struct sock *newsk);
 	int (*unix_may_send) (struct socket *sock, struct socket *other);
 
 	int (*socket_create) (int family, int type, int protocol, int kern);
@@ -2525,8 +2525,7 @@ static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32
 
 #ifdef CONFIG_SECURITY_NETWORK
 
-int security_unix_stream_connect(struct socket *sock, struct socket *other,
-				 struct sock *newsk);
+int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk);
 int security_unix_may_send(struct socket *sock,  struct socket *other);
 int security_socket_create(int family, int type, int protocol, int kern);
 int security_socket_post_create(struct socket *sock, int family,
@@ -2567,8 +2566,8 @@ void security_tun_dev_post_create(struct sock *sk);
 int security_tun_dev_attach(struct sock *sk);
 
 #else	/* CONFIG_SECURITY_NETWORK */
-static inline int security_unix_stream_connect(struct socket *sock,
-					       struct socket *other,
+static inline int security_unix_stream_connect(struct sock *sock,
+					       struct sock *other,
 					       struct sock *newsk)
 {
 	return 0;