syzbot is reporting use-after-free read in tcp_retransmit_timer() [1], for TCP socket used by RDS is accessing sock_net() without acquiring a refcount on net namespace. Since TCP's retransmission can happen after a process which created net namespace terminated, we need to explicitly acquire a refcount. Link: https://syzkaller.appspot.com/bug?extid=694120e1002c117747ed [1] Reported-by: syzbot <syzbot+694120e1002c117747ed@xxxxxxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Tested-by: syzbot <syzbot+694120e1002c117747ed@xxxxxxxxxxxxxxxxxxxxxxxxx> --- net/rds/tcp.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/rds/tcp.c b/net/rds/tcp.c index 5327d130c4b5..8015d2695784 100644 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c @@ -493,6 +493,15 @@ void rds_tcp_tune(struct socket *sock) struct net *net = sock_net(sk); struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid); + /* TCP timer functions might access net namespace even after + * a process which created this net namespace terminated. + */ + if (!sk->sk_net_refcnt) { + sk->sk_net_refcnt = 1; + get_net_track(net, &sk->ns_tracker, GFP_KERNEL); + sock_inuse_add(net, 1); + } + tcp_sock_set_nodelay(sock->sk); lock_sock(sk); if (rtn->sndbuf_size > 0) { -- 2.34.1
