[PATCH 5.17 005/114] net: rds: use maybe_get_net() when acquiring refcount on TCP sockets

Greg Kroah-Hartman
2022-05-16T20:28:59Z

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

[ Upstream commit 6997fbd7a3dafa754f81d541498ace35b43246d8 ]

Eric Dumazet is reporting addition on 0 problem at rds_tcp_tune(), for
delayed works queued in rds_wq might be invoked after a net namespace's
refcount already reached 0.

Since rds_tcp_exit_net() from cleanup_net() calls flush_workqueue(rds_wq),
it is guaranteed that we can instead use maybe_get_net() from delayed work
functions until rds_tcp_exit_net() returns.

Note that I'm not convinced that all works which might access a net
namespace are already queued in rds_wq by the moment rds_tcp_exit_net()
calls flush_workqueue(rds_wq). If some race is there, rds_tcp_exit_net()
will fail to wait for work functions, and kmem_cache_free() could be
called from net_free() before maybe_get_net() is called from
rds_tcp_tune().

Reported-by: Eric Dumazet <edumazet@google.com>
Fixes: 3a58f13a881ed351 ("net: rds: acquire refcount on TCP sockets")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/41d09faf-bc78-1a87-dfd1-c6d1b5984b61@I-love.SAKURA.ne.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/rds/tcp.c | 12 +++++++++---
net/rds/tcp.h | 2 +-
net/rds/tcp_connect.c | 5 ++++-
net/rds/tcp_listen.c | 5 ++++-
4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 2f638f8b7b1e..73ee2771093d 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -487,11 +487,11 @@ struct rds_tcp_net {
/* All module specific customizations to the RDS-TCP socket should be done in
* rds_tcp_tune() and applied after socket creation.
*/
-void rds_tcp_tune(struct socket *sock)
+bool rds_tcp_tune(struct socket *sock)
{
struct sock *sk = sock->sk;
struct net *net = sock_net(sk);
- struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
+ struct rds_tcp_net *rtn;

tcp_sock_set_nodelay(sock->sk);
lock_sock(sk);
@@ -499,10 +499,15 @@ void rds_tcp_tune(struct socket *sock)
* a process which created this net namespace terminated.
*/
if (!sk->sk_net_refcnt) {
+ if (!maybe_get_net(net)) {
+ release_sock(sk);
+ return false;
+ }
sk->sk_net_refcnt = 1;
- get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
+ netns_tracker_alloc(net, &sk->ns_tracker, GFP_KERNEL);
sock_inuse_add(net, 1);
}
+ rtn = net_generic(net, rds_tcp_netid);
if (rtn->sndbuf_size > 0) {
sk->sk_sndbuf = rtn->sndbuf_size;
sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
@@ -512,6 +517,7 @@ void rds_tcp_tune(struct socket *sock)
sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
}
release_sock(sk);
+ return true;
}

static void rds_tcp_accept_worker(struct work_struct *work)
diff --git a/net/rds/tcp.h b/net/rds/tcp.h
index dc8d745d6857..f8b5930d7b34 100644
--- a/net/rds/tcp.h
+++ b/net/rds/tcp.h
@@ -49,7 +49,7 @@ struct rds_tcp_statistics {
};

/* tcp.c */
-void rds_tcp_tune(struct socket *sock);
+bool rds_tcp_tune(struct socket *sock);
void rds_tcp_set_callbacks(struct socket *sock, struct rds_conn_path *cp);
void rds_tcp_reset_callbacks(struct socket *sock, struct rds_conn_path *cp);
void rds_tcp_restore_callbacks(struct socket *sock,
diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c
index 5461d77fff4f..f0c477c5d1db 100644
--- a/net/rds/tcp_connect.c
+++ b/net/rds/tcp_connect.c
@@ -124,7 +124,10 @@ int rds_tcp_conn_path_connect(struct rds_conn_path *cp)
if (ret < 0)
goto out;

- rds_tcp_tune(sock);
+ if (!rds_tcp_tune(sock)) {
+ ret = -EINVAL;
+ goto out;
+ }

if (isv6) {
sin6.sin6_family = AF_INET6;
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index 09cadd556d1e..7edf2e69d3fe 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -133,7 +133,10 @@ int rds_tcp_accept_one(struct socket *sock)
__module_get(new_sock->ops->owner);

rds_tcp_keepalive(new_sock);
- rds_tcp_tune(new_sock);
+ if (!rds_tcp_tune(new_sock)) {
+ ret = -EINVAL;
+ goto out;
+ }

inet = inet_sk(new_sock->sk);

--
2.35.1