On Sun, May 1, 2022 at 8:29 AM Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > > 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. > Please add a Fixes: tag > 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. > + */ Please move this after the lock_sock(sk) [1], so that we are protected correctly ? > + 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); [1] Here. > if (rtn->sndbuf_size > 0) { > -- > 2.34.1 >
