Patch "tcp: fix race in tcp_v6_syn_recv_sock()" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    tcp: fix race in tcp_v6_syn_recv_sock()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-fix-race-in-tcp_v6_syn_recv_sock.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 08b1020b8872acde665d8f403430b074297b8e10
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Thu Jun 6 15:46:51 2024 +0000

    tcp: fix race in tcp_v6_syn_recv_sock()
    
    [ Upstream commit d37fe4255abe8e7b419b90c5847e8ec2b8debb08 ]
    
    tcp_v6_syn_recv_sock() calls ip6_dst_store() before
    inet_sk(newsk)->pinet6 has been set up.
    
    This means ip6_dst_store() writes over the parent (listener)
    np->dst_cookie.
    
    This is racy because multiple threads could share the same
    parent and their final np->dst_cookie could be wrong.
    
    Move ip6_dst_store() call after inet_sk(newsk)->pinet6
    has been changed and after the copy of parent ipv6_pinfo.
    
    Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c18fdddbfa09d..c1f1fa6e33161 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1331,7 +1331,6 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
 	 */
 
 	newsk->sk_gso_type = SKB_GSO_TCPV6;
-	ip6_dst_store(newsk, dst, NULL, NULL);
 	inet6_sk_rx_dst_set(newsk, skb);
 
 	inet_sk(newsk)->pinet6 = tcp_inet6_sk(newsk);
@@ -1342,6 +1341,8 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
 
 	memcpy(newnp, np, sizeof(struct ipv6_pinfo));
 
+	ip6_dst_store(newsk, dst, NULL, NULL);
+
 	newsk->sk_v6_daddr = ireq->ir_v6_rmt_addr;
 	newnp->saddr = ireq->ir_v6_loc_addr;
 	newsk->sk_v6_rcv_saddr = ireq->ir_v6_loc_addr;




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