[PATCH stable 5.15] tcp: add a missing nf_reset_ct() in 3WHS handling

[PATCH stable 5.15] tcp: add a missing nf_reset_ct() in 3WHS handling

[Jakub Kicinski]

From: Eric Dumazet <edumazet@google.com>

commit 6f0012e35160cd08a53e46e3b3bbf724b92dfe68 upstream.

When the third packet of 3WHS connection establishment
contains payload, it is added into socket receive queue
without the XFRM check and the drop of connection tracking
context.

This means that if the data is left unread in the socket
receive queue, conntrack module can not be unloaded.

As most applications usually reads the incoming data
immediately after accept(), bug has been hiding for
quite a long time.

Commit 68822bdf76f1 ("net: generalize skb freeing
deferral to per-cpu lists") exposed this bug because
even if the application reads this data, the skb
with nfct state could stay in a per-cpu cache for
an arbitrary time, if said cpu no longer process RX softirqs.

Many thanks to Ilya Maximets for reporting this issue,
and for testing various patches:
https://lore.kernel.org/netdev/20220619003919.394622-1-i.maximets@ovn.org/

Note that I also added a missing xfrm4_policy_check() call,
although this is probably not a big issue, as the SYN
packet should have been dropped earlier.

Fixes: b59c270104f0 ("[NETFILTER]: Keep conntrack reference until IPsec policy checks are done")
Reported-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Tested-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Ilya Maximets <i.maximets@ovn.org>
Link: https://lore.kernel.org/r/20220623050436.1290307-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/ipv4/tcp_ipv4.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a189625098ba..5d94822fd506 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2014,7 +2014,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
 		struct sock *nsk;
 
 		sk = req->rsk_listener;
-		if (unlikely(tcp_v4_inbound_md5_hash(sk, skb, dif, sdif))) {
+		if (unlikely(!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb) ||
+			     tcp_v4_inbound_md5_hash(sk, skb, dif, sdif))) {
 			sk_drops_add(sk, skb);
 			reqsk_put(req);
 			goto discard_it;
@@ -2061,6 +2062,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
 			}
 			goto discard_and_relse;
 		}
+		nf_reset_ct(skb);
 		if (nsk == sk) {
 			reqsk_put(req);
 			tcp_v4_restore_cb(skb);
-- 
2.36.1

Re: [PATCH stable 5.15] tcp: add a missing nf_reset_ct() in 3WHS handling

[Greg KH]

On Thu, Jun 30, 2022 at 06:41:01PM -0700, Jakub Kicinski wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> commit 6f0012e35160cd08a53e46e3b3bbf724b92dfe68 upstream.
> 
> When the third packet of 3WHS connection establishment
> contains payload, it is added into socket receive queue
> without the XFRM check and the drop of connection tracking
> context.
> 
> This means that if the data is left unread in the socket
> receive queue, conntrack module can not be unloaded.
> 
> As most applications usually reads the incoming data
> immediately after accept(), bug has been hiding for
> quite a long time.
> 
> Commit 68822bdf76f1 ("net: generalize skb freeing
> deferral to per-cpu lists") exposed this bug because
> even if the application reads this data, the skb
> with nfct state could stay in a per-cpu cache for
> an arbitrary time, if said cpu no longer process RX softirqs.
> 
> Many thanks to Ilya Maximets for reporting this issue,
> and for testing various patches:
> https://lore.kernel.org/netdev/20220619003919.394622-1-i.maximets@ovn.org/
> 
> Note that I also added a missing xfrm4_policy_check() call,
> although this is probably not a big issue, as the SYN
> packet should have been dropped earlier.
> 
> Fixes: b59c270104f0 ("[NETFILTER]: Keep conntrack reference until IPsec policy checks are done")
> Reported-by: Ilya Maximets <i.maximets@ovn.org>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Florian Westphal <fw@strlen.de>
> Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> Cc: Steffen Klassert <steffen.klassert@secunet.com>
> Tested-by: Ilya Maximets <i.maximets@ovn.org>
> Reviewed-by: Ilya Maximets <i.maximets@ovn.org>
> Link: https://lore.kernel.org/r/20220623050436.1290307-1-edumazet@google.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
>  net/ipv4/tcp_ipv4.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Now queued up, thanks.

greg k-h