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authorEric Dumazet <edumazet@google.com>2022-04-29 18:15:23 -0700
committerDavid S. Miller <davem@davemloft.net>2022-04-30 13:25:29 +0100
commit783d108dd71d97e4cac5fe8ce70ca43ed7dc7bb7 (patch)
treed5ccf3197675cf26ff4e9250544b4a3a84ed4b88 /net/ipv4/tcp_input.c
parent90e29e592ec95c5c2af6fe73896dba40303728cf (diff)
tcp: drop skb dst in tcp_rcv_established()
In commit f84af32cbca7 ("net: ip_queue_rcv_skb() helper") I dropped the skb dst in tcp_data_queue(). This only dealt with so-called TCP input slow path. When fast path is taken, tcp_rcv_established() calls tcp_queue_rcv() while skb still has a dst. This was mostly fine, because most dsts at this point are not refcounted (thanks to early demux) However, TCP packets sent over loopback have refcounted dst. Then commit 68822bdf76f1 ("net: generalize skb freeing deferral to per-cpu lists") came and had the effect of delaying skb freeing for an arbitrary time. If during this time the involved netns is dismantled, cleanup_net() frees the struct net with embedded net->ipv6.ip6_dst_ops. Then when eventually dst_destroy_rcu() is called, if (dst->ops->destroy) ... triggers an use-after-free. It is not clear if ip6_route_net_exit() lacks a rcu_barrier() as syzbot reported similar issues before the blamed commit. ( https://groups.google.com/g/syzkaller-bugs/c/CofzW4eeA9A/m/009WjumTAAAJ ) Fixes: 68822bdf76f1 ("net: generalize skb freeing deferral to per-cpu lists") Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cc3de8dc5797..97cfcd85f84e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5928,6 +5928,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS);
/* Bulk data transfer: receiver */
+ skb_dst_drop(skb);
__skb_pull(skb, tcp_header_len);
eaten = tcp_queue_rcv(sk, skb, &fragstolen);