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Message-ID: <20230120125955.3453768-3-edumazet@google.com>
Date: Fri, 20 Jan 2023 12:59:54 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 2/3] 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@...gle.com>
---
net/netlink/af_netlink.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 4aea89f7d700a587c4e9017cdff76cd3fe93ed7a..b5b8c6a5fc34205c849ab2ca105cc44ffb407623 100644
--- 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() */
--
2.39.1.405.gd4c25cc71f-goog
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