[PATCH v2] RDMA/cxgb4: Fix potential null-ptr-deref in pass_establish()

[Nikita Zhandarovich]

If get_ep_from_tid() fails to lookup non-NULL value for ep, ep is
dereferenced later regardless of whether it is empty.
This patch adds a simple sanity check to fix the issue.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 944661dd97f4 ("RDMA/iw_cxgb4: atomically lookup ep and get a reference")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
---
v2: do not use pr_warn() when get_ep_from_tid() returns NULL as
Jason Gunthorpe <jgg@xxxxxxxx> suggested.

 drivers/infiniband/hw/cxgb4/cm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/hw/cxgb4/cm.c b/drivers/infiniband/hw/cxgb4/cm.c
index 499a425a3379..f5f4579f037c 100644
--- a/drivers/infiniband/hw/cxgb4/cm.c
+++ b/drivers/infiniband/hw/cxgb4/cm.c
@@ -2676,6 +2676,8 @@ static int pass_establish(struct c4iw_dev *dev, struct sk_buff *skb)
 	u16 tcp_opt = ntohs(req->tcp_opt);
 
 	ep = get_ep_from_tid(dev, tid);
+	if (!ep)
+		return 0;
 	pr_debug("ep %p tid %u\n", ep, ep->hwtid);
 	ep->snd_seq = be32_to_cpu(req->snd_isn);
 	ep->rcv_seq = be32_to_cpu(req->rcv_isn);
-- 
2.25.1