Merge: RDMA/rxe: Fix seg fault in rxe_comp_queue_pkt

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/4628

JIRA: https://issues.redhat.com/browse/RHEL-44248  
CVE: CVE-2024-38544  
  
commit 2b23b60  
Author: Bob Pearson <rpearsonhpe@gmail.com>  
Date:   Fri Mar 29 09:55:04 2024 -0500  
  
    RDMA/rxe: Fix seg fault in rxe_comp_queue_pkt  
  
    In rxe_comp_queue_pkt() an incoming response packet skb is enqueued to the  
    resp_pkts queue and then a decision is made whether to run the completer  
    task inline or schedule it. Finally the skb is dereferenced to bump a 'hw'  
    performance counter. This is wrong because if the completer task is  
    already running in a separate thread it may have already processed the skb  
    and freed it which can cause a seg fault.  This has been observed  
    infrequently in testing at high scale.  
  
    This patch fixes this by changing the order of enqueuing the packet until  
    after the counter is accessed.  
  
    Link: https://lore.kernel.org/r/20240329145513.35381-4-rpearsonhpe@gmail.com  
    Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>  
    Fixes: 0b1e5b9 ("IB/rxe: Add port protocol stats")  
    Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>  
  
Signed-off-by: Kamal Heib <kheib@redhat.com>

Approved-by: José Ignacio Tornos Martínez <jtornosm@redhat.com>
Approved-by: John B. Wyatt IV <jwyatt@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Lucas Zampieri <lzampier@redhat.com>

Author: zampierilucas

drivers/infiniband/sw/rxe/rxe_comp.c

@@ -131,12 +131,12 @@ void rxe_comp_queue_pkt(struct rxe_qp *qp, struct sk_buff *skb)
 {
 	int must_sched;
 
-	skb_queue_tail(&qp->resp_pkts, skb);
-
-	must_sched = skb_queue_len(&qp->resp_pkts) > 1;
+	must_sched = skb_queue_len(&qp->resp_pkts) > 0;
 	if (must_sched != 0)
 		rxe_counter_inc(SKB_TO_PKT(skb)->rxe, RXE_CNT_COMPLETER_SCHED);
 
+	skb_queue_tail(&qp->resp_pkts, skb);
+
 	if (must_sched)
 		rxe_sched_task(&qp->comp.task);
 	else