netlink: annotate data races around dst_portid and dst_group

netlink_getname(), netlink_sendmsg() and netlink_getsockbyportid()
can read nlk->dst_portid and nlk->dst_group while another
thread is changing them.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 4aea89f..b5b8c6a 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1099,8 +1099,9 @@ static int netlink_connect(struct socket *sock, struct sockaddr *addr,
 
        if (addr->sa_family == AF_UNSPEC) {
                sk->sk_state    = NETLINK_UNCONNECTED;
-               nlk->dst_portid = 0;
-               nlk->dst_group  = 0;
+               /* dst_portid and dst_group can be read locklessly */
+               WRITE_ONCE(nlk->dst_portid, 0);
+               WRITE_ONCE(nlk->dst_group, 0);
                return 0;
        }
        if (addr->sa_family != AF_NETLINK)
@@ -1122,8 +1123,9 @@ static int netlink_connect(struct socket *sock, struct sockaddr *addr,
 
        if (err == 0) {
                sk->sk_state    = NETLINK_CONNECTED;
-               nlk->dst_portid = nladdr->nl_pid;
-               nlk->dst_group  = ffs(nladdr->nl_groups);
+               /* dst_portid and dst_group can be read locklessly */
+               WRITE_ONCE(nlk->dst_portid, nladdr->nl_pid);
+               WRITE_ONCE(nlk->dst_group, ffs(nladdr->nl_groups));
        }
 
        return err;
@@ -1140,8 +1142,9 @@ static int netlink_getname(struct socket *sock, struct sockaddr *addr,
        nladdr->nl_pad = 0;
 
        if (peer) {
-               nladdr->nl_pid = nlk->dst_portid;
-               nladdr->nl_groups = netlink_group_mask(nlk->dst_group);
+               /* Paired with WRITE_ONCE() in netlink_connect() */
+               nladdr->nl_pid = READ_ONCE(nlk->dst_portid);
+               nladdr->nl_groups = netlink_group_mask(READ_ONCE(nlk->dst_group));
        } else {
                /* Paired with WRITE_ONCE() in netlink_insert() */
                nladdr->nl_pid = READ_ONCE(nlk->portid);
@@ -1171,8 +1174,9 @@ static struct sock *netlink_getsockbyportid(struct sock *ssk, u32 portid)
 
        /* Don't bother queuing skb if kernel socket has no input function */
        nlk = nlk_sk(sock);
+       /* dst_portid can be changed in netlink_connect() */
        if (sock->sk_state == NETLINK_CONNECTED &&
-           nlk->dst_portid != nlk_sk(ssk)->portid) {
+           READ_ONCE(nlk->dst_portid) != nlk_sk(ssk)->portid) {
                sock_put(sock);
                return ERR_PTR(-ECONNREFUSED);
        }
@@ -1889,8 +1893,9 @@ static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
                        goto out;
                netlink_skb_flags |= NETLINK_SKB_DST;
        } else {
-               dst_portid = nlk->dst_portid;
-               dst_group = nlk->dst_group;
+               /* Paired with WRITE_ONCE() in netlink_connect() */
+               dst_portid = READ_ONCE(nlk->dst_portid);
+               dst_group = READ_ONCE(nlk->dst_group);
        }
 
        /* Paired with WRITE_ONCE() in netlink_insert() */