net: llc: add lock_sock in llc_ui_bind to avoid a race condition

There is a race condition in llc_ui_bind if two or more processes/threads
try to bind a same socket.

If more processes/threads bind a same socket success that will lead to
two problems, one is this action is not what we expected, another is
will lead to kernel in unstable status or oops(in my simple test case,
cause llc2.ko can't unload).

The current code is test SOCK_ZAPPED bit to avoid a process to
bind a same socket twice but that is can't avoid more processes/threads
try to bind a same socket at the same time.

So, add lock_sock in llc_ui_bind like others, such as llc_ui_connect.

Signed-off-by: Lin Zhang <xiaolou4617@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 8364fe5b59e4ca01ef8d05b1038dbe96fedf657b..c38d16f22d2a7ff265b8729d43b164312598fd9f 100644 (file)
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -311,6 +311,8 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
        int rc = -EINVAL;
 
        dprintk("%s: binding %02X\n", __func__, addr->sllc_sap);
+
+       lock_sock(sk);
        if (unlikely(!sock_flag(sk, SOCK_ZAPPED) || addrlen != sizeof(*addr)))
                goto out;
        rc = -EAFNOSUPPORT;
@@ -382,6 +384,7 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
 out_put:
        llc_sap_put(sap);
 out:
+       release_sock(sk);
        return rc;
 }