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From:   Jakob Koschel <jakobkoschel@gmail.com>
To:     Greg Kroah-Hartman <greg@kroah.com>
Cc:     Jakob Koschel <jakobkoschel@gmail.com>,
        linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Felipe Balbi <balbi@kernel.org>, Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Claudiu Beznea <claudiu.beznea@microchip.com>,
        Cristian Birsan <cristian.birsan@microchip.com>,
        Al Cooper <alcooperx@gmail.com>, Li Yang <leoyang.li@nxp.com>,
        Vladimir Zapolskiy <vz@mleia.com>,
        Daniel Mack <daniel@zonque.org>,
        Haojian Zhuang <haojian.zhuang@gmail.com>,
        Robert Jarzmik <robert.jarzmik@free.fr>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Michal Simek <michal.simek@xilinx.com>,
        linux-usb@vger.kernel.org (open list:USB GADGET/PERIPHERAL SUBSYSTEM),
        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 v2 17/26] usb: gadget: configfs: remove using list iterator after loop body as a ptr
Date:   Tue,  8 Mar 2022 18:18:09 +0100
Message-Id: <20220308171818.384491-18-jakobkoschel@gmail.com>
In-Reply-To: <20220308171818.384491-1-jakobkoschel@gmail.com>
References: <20220308171818.384491-1-jakobkoschel@gmail.com>
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If the list does not contain the expected element, the value of
list_for_each_entry() iterator will not point to a valid structure.
To avoid type confusion in such case, the list iterator
scope will be limited to list_for_each_entry() loop.

In preparation to limiting scope of a list iterator to the list traversal
loop, use a dedicated pointer to point to the found element [1].
Determining if an element was found is then simply checking if
the pointer is != NULL instead of using the potentially bogus pointer.

Link: https://lore.kernel.org/all/YhdfEIwI4EdtHdym@kroah.com/
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
---
 drivers/usb/gadget/configfs.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index d4a678c0806e..1fb837d9271e 100644
--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -418,7 +418,7 @@ static int config_usb_cfg_link(
 
 	struct usb_function_instance *fi =
 			to_usb_function_instance(usb_func_ci);
-	struct usb_function_instance *a_fi;
+	struct usb_function_instance *a_fi = NULL, *iter;
 	struct usb_function *f;
 	int ret;
 
@@ -428,11 +428,13 @@ static int config_usb_cfg_link(
 	 * from another gadget or a random directory.
 	 * Also a function instance can only be linked once.
 	 */
-	list_for_each_entry(a_fi, &gi->available_func, cfs_list) {
-		if (a_fi == fi)
-			break;
+	list_for_each_entry(iter, &gi->available_func, cfs_list) {
+		if (iter != fi)
+			continue;
+		a_fi = iter;
+		break;
 	}
-	if (a_fi != fi) {
+	if (!a_fi) {
 		ret = -EINVAL;
 		goto out;
 	}
@@ -882,15 +884,17 @@ static int os_desc_link(struct config_item *os_desc_ci,
 	struct gadget_info *gi = os_desc_item_to_gadget_info(os_desc_ci);
 	struct usb_composite_dev *cdev = &gi->cdev;
 	struct config_usb_cfg *c_target = to_config_usb_cfg(usb_cfg_ci);
-	struct usb_configuration *c;
+	struct usb_configuration *c = NULL, *iter;
 	int ret;
 
 	mutex_lock(&gi->lock);
-	list_for_each_entry(c, &cdev->configs, list) {
-		if (c == &c_target->c)
-			break;
+	list_for_each_entry(iter, &cdev->configs, list) {
+		if (iter != &c_target->c)
+			continue;
+		c = iter;
+		break;
 	}
-	if (c != &c_target->c) {
+	if (!c) {
 		ret = -EINVAL;
 		goto out;
 	}
-- 
2.25.1