linux-kernel - [PATCH] cxgb4: cm: fix a incorrect NULL check on list iterator

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Date:   Sun, 27 Mar 2022 15:35:42 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     bharat@...lsio.com, jgg@...pe.ca
Cc:     vipul@...lsio.com, roland@...estorage.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiaomeng Tong <xiam0nd.tong@...il.com>, stable@...r.kernel.org
Subject: [PATCH] cxgb4: cm: fix a incorrect NULL check on list iterator

The bug is here:
	if (!pdev) {

The list iterator value 'pdev' will *always* be set and non-NULL
by for_each_netdev(), so it is incorrect to assume that the
iterator value will be NULL if the list is empty or no element
found (in this case, the check 'if (!pdev)' can be bypassed as
it always be false unexpectly).

To fix the bug, use a new variable 'iter' as the list iterator,
while use the original variable 'pdev' as a dedicated pointer to
point to the found element.

Cc: stable@...r.kernel.org
Fixes: 830662f6f032f ("RDMA/cxgb4: Add support for active and passive open connection with IPv6 address")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
---
 drivers/infiniband/hw/cxgb4/cm.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/hw/cxgb4/cm.c b/drivers/infiniband/hw/cxgb4/cm.c
index c16017f6e8db..870d8517310b 100644
--- a/drivers/infiniband/hw/cxgb4/cm.c
+++ b/drivers/infiniband/hw/cxgb4/cm.c
@@ -2071,7 +2071,7 @@ static int import_ep(struct c4iw_ep *ep, int iptype, __u8 *peer_ip,
 {
 	struct neighbour *n;
 	int err, step;
-	struct net_device *pdev;
+	struct net_device *pdev = NULL, *iter;
 
 	n = dst_neigh_lookup(dst, peer_ip);
 	if (!n)
@@ -2083,14 +2083,14 @@ static int import_ep(struct c4iw_ep *ep, int iptype, __u8 *peer_ip,
 		if (iptype == 4)
 			pdev = ip_dev_find(&init_net, *(__be32 *)peer_ip);
 		else if (IS_ENABLED(CONFIG_IPV6))
-			for_each_netdev(&init_net, pdev) {
+			for_each_netdev(&init_net, iter) {
 				if (ipv6_chk_addr(&init_net,
 						  (struct in6_addr *)peer_ip,
-						  pdev, 1))
+						  iter, 1)) {
+					pdev = iter;
 					break;
+				}
 			}
-		else
-			pdev = NULL;
 
 		if (!pdev) {
 			err = -ENODEV;
-- 
2.17.1