linux-kernel - [PATCH] crypto: cavium/nitrox - remove check of list iterator against head past the loop body

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Date:   Thu, 31 Mar 2022 23:59:10 +0200
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Amey Narkhede <ameynarkhede03@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Lee Jones <lee.jones@...aro.org>, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...nel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jakobkoschel@...il.com>
Subject: [PATCH] crypto: cavium/nitrox - remove check of list iterator against head past the loop body

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@...il.com>
---
 drivers/crypto/cavium/nitrox/nitrox_main.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/cavium/nitrox/nitrox_main.c b/drivers/crypto/cavium/nitrox/nitrox_main.c
index 6c61817996a3..432a61aca0c5 100644
--- a/drivers/crypto/cavium/nitrox/nitrox_main.c
+++ b/drivers/crypto/cavium/nitrox/nitrox_main.c
@@ -269,15 +269,17 @@ static void nitrox_remove_from_devlist(struct nitrox_device *ndev)
 
 struct nitrox_device *nitrox_get_first_device(void)
 {
-	struct nitrox_device *ndev;
+	struct nitrox_device *ndev = NULL, *iter;
 
 	mutex_lock(&devlist_lock);
-	list_for_each_entry(ndev, &ndevlist, list) {
-		if (nitrox_ready(ndev))
+	list_for_each_entry(iter, &ndevlist, list) {
+		if (nitrox_ready(iter)) {
+			ndev = iter;
 			break;
+		}
 	}
 	mutex_unlock(&devlist_lock);
-	if (&ndev->list == &ndevlist)
+	if (!ndev)
 		return NULL;
 
 	refcount_inc(&ndev->refcnt);

base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275
-- 
2.25.1