Patch "netfilter: conntrack: check SCTP_CID_SHUTDOWN_ACK for vtag setting in sctp_new" has been added to the 6.1-stable tree

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

    netfilter: conntrack: check SCTP_CID_SHUTDOWN_ACK for vtag setting in sctp_new

to the 6.1-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:
     netfilter-conntrack-check-sctp_cid_shutdown_ack-for-.patch
and it can be found in the queue-6.1 subdirectory.

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



commit 30463be1f5889de4302158089ff283e8cbb9aea6
Author: Xin Long <lucien.xin@xxxxxxxxx>
Date:   Thu Jan 25 17:29:46 2024 -0500

    netfilter: conntrack: check SCTP_CID_SHUTDOWN_ACK for vtag setting in sctp_new
    
    [ Upstream commit 6e348067ee4bc5905e35faa3a8fafa91c9124bc7 ]
    
    The annotation says in sctp_new(): "If it is a shutdown ack OOTB packet, we
    expect a return shutdown complete, otherwise an ABORT Sec 8.4 (5) and (8)".
    However, it does not check SCTP_CID_SHUTDOWN_ACK before setting vtag[REPLY]
    in the conntrack entry(ct).
    
    Because of that, if the ct in Router disappears for some reason in [1]
    with the packet sequence like below:
    
       Client > Server: sctp (1) [INIT] [init tag: 3201533963]
       Server > Client: sctp (1) [INIT ACK] [init tag: 972498433]
       Client > Server: sctp (1) [COOKIE ECHO]
       Server > Client: sctp (1) [COOKIE ACK]
       Client > Server: sctp (1) [DATA] (B)(E) [TSN: 3075057809]
       Server > Client: sctp (1) [SACK] [cum ack 3075057809]
       Server > Client: sctp (1) [HB REQ]
       (the ct in Router disappears somehow)  <-------- [1]
       Client > Server: sctp (1) [HB ACK]
       Client > Server: sctp (1) [DATA] (B)(E) [TSN: 3075057810]
       Client > Server: sctp (1) [DATA] (B)(E) [TSN: 3075057810]
       Client > Server: sctp (1) [HB REQ]
       Client > Server: sctp (1) [DATA] (B)(E) [TSN: 3075057810]
       Client > Server: sctp (1) [HB REQ]
       Client > Server: sctp (1) [ABORT]
    
    when processing HB ACK packet in Router it calls sctp_new() to initialize
    the new ct with vtag[REPLY] set to HB_ACK packet's vtag.
    
    Later when sending DATA from Client, all the SACKs from Server will get
    dropped in Router, as the SACK packet's vtag does not match vtag[REPLY]
    in the ct. The worst thing is the vtag in this ct will never get fixed
    by the upcoming packets from Server.
    
    This patch fixes it by checking SCTP_CID_SHUTDOWN_ACK before setting
    vtag[REPLY] in the ct in sctp_new() as the annotation says. With this
    fix, it will leave vtag[REPLY] in ct to 0 in the case above, and the
    next HB REQ/ACK from Server is able to fix the vtag as its value is 0
    in nf_conntrack_sctp_packet().
    
    Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
    Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index c94a9971d790c..7ffd698497f2a 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -299,7 +299,7 @@ sctp_new(struct nf_conn *ct, const struct sk_buff *skb,
 			pr_debug("Setting vtag %x for secondary conntrack\n",
 				 sh->vtag);
 			ct->proto.sctp.vtag[IP_CT_DIR_ORIGINAL] = sh->vtag;
-		} else {
+		} else if (sch->type == SCTP_CID_SHUTDOWN_ACK) {
 		/* If it is a shutdown ack OOTB packet, we expect a return
 		   shutdown complete, otherwise an ABORT Sec 8.4 (5) and (8) */
 			pr_debug("Setting vtag %x for new conn OOTB\n",




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