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net/rds: Fix NULL pointer dereference in rds_tcp_accept_one

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Save a local pointer to new_sock->sk and hold a reference before
installing callbacks in rds_tcp_accept_one. After
rds_tcp_set_callbacks() or rds_tcp_reset_callbacks(), tc->t_sock is
set to new_sock which may race with the shutdown path.  A concurrent
rds_tcp_conn_path_shutdown() may call sock_release(), which sets
new_sock->sk = NULL and may eventually free sk when the refcount
reaches zero.

Subsequent accesses to new_sock->sk->sk_state would dereference NULL,
causing the crash. The fix saves a local sk pointer before callbacks
are installed so that sk_state can be accessed safely even after
new_sock->sk is nulled, and uses sock_hold()/sock_put() to ensure
sk itself remains valid for the duration.

Fixes: 826c1004d4 ("net/rds: rds_tcp_conn_path_shutdown must not discard messages")
Reported-by: syzbot+96046021045ffe6d7709@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=96046021045ffe6d7709
Signed-off-by: Allison Henderson <achender@kernel.org>
Link: https://patch.msgid.link/20260216222643.2391390-1-achender@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Allison Henderson 2026-02-16 15:26:43 -07:00 • committed by Paolo Abeni
parent 45be47bf5d
commit 6bf45704a9
1 changed files with 17 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

20
net/rds/tcp_listen.c
View file

@ -177,6 +177,7 @@ int rds_tcp_accept_one(struct rds_tcp_net *rtn)
struct rds_tcp_connection *rs_tcp = NULL;
int conn_state;
struct rds_conn_path *cp;
struct sock *sk;
struct in6_addr *my_addr, *peer_addr;
#if !IS_ENABLED(CONFIG_IPV6)
struct in6_addr saddr, daddr;
@ -298,6 +299,17 @@ int rds_tcp_accept_one(struct rds_tcp_net *rtn)
rds_conn_path_drop(cp, 0);
goto rst_nsk;
}
/* Save a local pointer to sk and hold a reference before setting
* callbacks. Once callbacks are set, a concurrent
* rds_tcp_conn_path_shutdown() may call sock_release(), which
* sets new_sock->sk to NULL and drops a reference on sk.
* The local pointer lets us safely access sk_state below even
* if new_sock->sk has been nulled, and sock_hold() keeps sk
* itself valid until we are done.
*/
sk = new_sock->sk;
sock_hold(sk);
if (rs_tcp->t_sock) {
/* Duelling SYN has been handled in rds_tcp_accept_one() */
rds_tcp_reset_callbacks(new_sock, cp);
@ -316,13 +328,15 @@ int rds_tcp_accept_one(struct rds_tcp_net *rtn)
* knowing that "rds_tcp_conn_path_shutdown" will
* dequeue pending messages.
*/
if (new_sock->sk->sk_state == TCP_CLOSE_WAIT ||
new_sock->sk->sk_state == TCP_LAST_ACK ||
new_sock->sk->sk_state == TCP_CLOSE)
if (READ_ONCE(sk->sk_state) == TCP_CLOSE_WAIT ||
READ_ONCE(sk->sk_state) == TCP_LAST_ACK ||
READ_ONCE(sk->sk_state) == TCP_CLOSE)
rds_conn_path_drop(cp, 0);
else
queue_delayed_work(cp->cp_wq, &cp->cp_recv_w, 0);
sock_put(sk);
new_sock = NULL;
ret = 0;
if (conn->c_npaths == 0)