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From:   Jakob Koschel <jakobkoschel@gmail.com>
To:     "David S. Miller" <davem@davemloft.net>
Cc:     Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
        Andrew Lunn <andrew@lunn.ch>,
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        Mike Rapoport <rppt@kernel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@gmail.com>,
        Cristiano Giuffrida <c.giuffrida@vu.nl>,
        "Bos, H.J." <h.j.bos@vu.nl>
Subject: [PATCH net-next v2 13/18] net: qede: Remove check of list iterator against head past the loop body
Date:   Tue, 12 Apr 2022 12:58:25 +0200
Message-Id: <20220412105830.3495846-14-jakobkoschel@gmail.com>
In-Reply-To: <20220412105830.3495846-1-jakobkoschel@gmail.com>
References: <20220412105830.3495846-1-jakobkoschel@gmail.com>
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When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.

While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
---
 drivers/net/ethernet/qlogic/qede/qede_filter.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qede/qede_filter.c b/drivers/net/ethernet/qlogic/qede/qede_filter.c
index 3010833ddde3..3d167e37e654 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_filter.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_filter.c
@@ -829,18 +829,21 @@ int qede_configure_vlan_filters(struct qede_dev *edev)
 int qede_vlan_rx_kill_vid(struct net_device *dev, __be16 proto, u16 vid)
 {
 	struct qede_dev *edev = netdev_priv(dev);
-	struct qede_vlan *vlan;
+	struct qede_vlan *vlan = NULL;
+	struct qede_vlan *iter;
 	int rc = 0;
 
 	DP_VERBOSE(edev, NETIF_MSG_IFDOWN, "Removing vlan 0x%04x\n", vid);
 
 	/* Find whether entry exists */
 	__qede_lock(edev);
-	list_for_each_entry(vlan, &edev->vlan_list, list)
-		if (vlan->vid == vid)
+	list_for_each_entry(iter, &edev->vlan_list, list)
+		if (iter->vid == vid) {
+			vlan = iter;
 			break;
+		}
 
-	if (list_entry_is_head(vlan, &edev->vlan_list, list)) {
+	if (!vlan) {
 		DP_VERBOSE(edev, (NETIF_MSG_IFUP | NETIF_MSG_IFDOWN),
 			   "Vlan isn't configured\n");
 		goto out;
-- 
2.25.1