Commit c8f7244c authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: tcp_child_process() related UAF 



tcp_child_process( .. child ...) currently calls sock_put(child).

Unfortunately @child (named @nsk in callers) can be used after
this point to send a RST packet.

To fix this UAF, I remove the sock_put() from tcp_child_process()
and let the callers handle this after it is safe.

Remove @rsk variable in tcp_v4_do_rcv() and change tcp_v6_do_rcv()
so that both functions look the same.

Fixes: cfb6eeb4 ("[TCP]: MD5 Signature Option (RFC2385) support.")
Reported-by: default avatarDamiano Melotti <melotti@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260505153927.3435532-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 770b136f

net/ipv4/tcp_ipv4.c

+6 −8
Original line number Diff line number Diff line
@@ -1827,7 +1827,6 @@ INDIRECT_CALLABLE_DECLARE(struct dst_entry *ipv4_dst_check(struct dst_entry *, 
int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)

{

	enum skb_drop_reason reason;

	struct sock *rsk;



	reason = psp_sk_rx_policy_check(sk, skb);

	if (reason)
@@ -1863,24 +1862,21 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb) 
			return 0;

		if (nsk != sk) {

			reason = tcp_child_process(sk, nsk, skb);

			if (reason) {

				rsk = nsk;

			sock_put(nsk);

			if (reason)

				goto reset;

			}

			return 0;

		}

	} else

		sock_rps_save_rxhash(sk, skb);



	reason = tcp_rcv_state_process(sk, skb);

	if (reason) {

		rsk = sk;

	if (reason)

		goto reset;

	}

	return 0;



reset:

	tcp_v4_send_reset(rsk, skb, sk_rst_convert_drop_reason(reason));

	tcp_v4_send_reset(sk, skb, sk_rst_convert_drop_reason(reason));

discard:

	sk_skb_reason_drop(sk, skb, reason);

	/* Be careful here. If this function gets more complicated and
@@ -2193,8 +2189,10 @@ int tcp_v4_rcv(struct sk_buff *skb) 


				rst_reason = sk_rst_convert_drop_reason(drop_reason);

				tcp_v4_send_reset(nsk, skb, rst_reason);

				sock_put(nsk);

				goto discard_and_relse;

			}

			sock_put(nsk);

			sock_put(sk);

			return 0;

		}

net/ipv4/tcp_minisocks.c

+1 −1
Original line number Diff line number Diff line
@@ -1012,6 +1012,6 @@ enum skb_drop_reason tcp_child_process(struct sock *parent, struct sock *child, 
	}



	bh_unlock_sock(child);

	sock_put(child);



	return reason;

}

net/ipv6/tcp_ipv6.c

+8 −5
Original line number Diff line number Diff line
@@ -1617,12 +1617,13 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb) 
	if (sk->sk_state == TCP_LISTEN) {

		struct sock *nsk = tcp_v6_cookie_check(sk, skb);



		if (!nsk)

			return 0;

		if (nsk != sk) {

			if (nsk) {

			reason = tcp_child_process(sk, nsk, skb);

			sock_put(nsk);

			if (reason)

				goto reset;

			}

			return 0;

		}

	} else
@@ -1827,8 +1828,10 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb) 


				rst_reason = sk_rst_convert_drop_reason(drop_reason);

				tcp_v6_send_reset(nsk, skb, rst_reason);

				sock_put(nsk);

				goto discard_and_relse;

			}

			sock_put(nsk);

			sock_put(sk);

			return 0;

		}