Re: [PATCHv2 1/1] IB/rxe: avoid double kfree_skb

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On 2018/4/26 12:41, Zhu Yanjun wrote:
When skb is sent, it will pass the following functions in soft roce.

rxe_send [rdma_rxe]
     ip_local_out
         __ip_local_out
         ip_output
             ip_finish_output
                 ip_finish_output2
                     dev_queue_xmit
                         __dev_queue_xmit
                             dev_hard_start_xmit

In the above functions, if error occurs in the above functions or
iptables rules drop skb after ip_local_out, kfree_skb will be called.
So it is not necessary to call kfree_skb in soft roce module again.
Or else crash will occur.

The steps to reproduce:

      server                       client
     ---------                    ---------
     |1.1.1.1|<----rxe-channel--->|1.1.1.2|
     ---------                    ---------

On server: rping -s -a 1.1.1.1 -v -C 10000 -S 512
On client: rping -c -a 1.1.1.1 -v -C 10000 -S 512

The kernel configs CONFIG_DEBUG_KMEMLEAK and
CONFIG_DEBUG_OBJECTS are enabled on both server and client.

When rping runs, run the following command in server:

iptables -I OUTPUT -p udp  --dport 4791 -j DROP

Without this patch, crash will occur.

CC: Srinivas Eeda <srinivas.eeda@xxxxxxxxxx>
CC: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Signed-off-by: Zhu Yanjun <yanjun.zhu@xxxxxxxxxx>
Reviewed-by: Yuval Shaia <yuval.shaia@xxxxxxxxxx>
---
V1->V2: Not only the dropped skb is freed, but also the error skb
         is also freed. So in soft roce, it is not necessary to call
         kfree_skb again.
---
  drivers/infiniband/sw/rxe/rxe_req.c  | 1 -
  drivers/infiniband/sw/rxe/rxe_resp.c | 6 +-----
  2 files changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_req.c b/drivers/infiniband/sw/rxe/rxe_req.c
index 7bdaf71..7851999 100644
--- a/drivers/infiniband/sw/rxe/rxe_req.c
+++ b/drivers/infiniband/sw/rxe/rxe_req.c
@@ -728,7 +728,6 @@ int rxe_requester(void *arg)
  		rollback_state(wqe, qp, &rollback_wqe, rollback_psn);
if (ret == -EAGAIN) {
-			kfree_skb(skb);
  			rxe_run_task(&qp->req.task, 1);
  			goto exit;
  		}
diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
index a65c996..955ff3b 100644
--- a/drivers/infiniband/sw/rxe/rxe_resp.c
+++ b/drivers/infiniband/sw/rxe/rxe_resp.c
@@ -742,7 +742,6 @@ static enum resp_states read_reply(struct rxe_qp *qp,
  	err = rxe_xmit_packet(rxe, qp, &ack_pkt, skb);
  	if (err) {
  		pr_err("Failed sending RDMA reply.\n");
-		kfree_skb(skb);
  		return RESPST_ERR_RNR;
  	}
@@ -954,10 +953,8 @@ static int send_ack(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
  	}
err = rxe_xmit_packet(rxe, qp, &ack_pkt, skb);
-	if (err) {
+	if (err)
  		pr_err_ratelimited("Failed sending ack\n");
-		kfree_skb(skb);
-	}
err1:
  	return err;
@@ -1141,7 +1138,6 @@ static enum resp_states duplicate_request(struct rxe_qp *qp,
  			if (rc) {
  				pr_err("Failed resending result. This flow is not handled - skb ignored\n");
  				rxe_drop_ref(qp);
-				kfree_skb(skb_copy);
  				rc = RESPST_CLEANUP;
  				goto out;
  			}

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