linux-kernel - [PATCH] char: misc: remove usage of list iterator past the loop body

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Date:   Sat, 19 Mar 2022 21:14:54 +0100
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Jakob Koschel <jakobkoschel@...il.com>,
        linux-kernel@...r.kernel.org, Greg Kroah-Hartman <greg@...ah.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: [PATCH] char: misc: remove usage of list iterator past the loop body

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

Link: https://lore.kernel.org/all/YhdfEIwI4EdtHdym@kroah.com/
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 drivers/char/misc.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index ca5141ed5ef3..cba19bfdc44d 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -100,17 +100,18 @@ static const struct seq_operations misc_seq_ops = {
 static int misc_open(struct inode *inode, struct file *file)
 {
 	int minor = iminor(inode);
-	struct miscdevice *c;
+	struct miscdevice *c = NULL, *iter;
 	int err = -ENODEV;
 	const struct file_operations *new_fops = NULL;

 	mutex_lock(&misc_mtx);

-	list_for_each_entry(c, &misc_list, list) {
-		if (c->minor == minor) {
-			new_fops = fops_get(c->fops);
-			break;
-		}
+	list_for_each_entry(iter, &misc_list, list) {
+		if (iter->minor != minor)
+			continue;
+		c = iter;
+		new_fops = fops_get(iter->fops);
+		break;
 	}

 	if (!new_fops) {
@@ -118,11 +119,12 @@ static int misc_open(struct inode *inode, struct file *file)
 		request_module("char-major-%d-%d", MISC_MAJOR, minor);
 		mutex_lock(&misc_mtx);

-		list_for_each_entry(c, &misc_list, list) {
-			if (c->minor == minor) {
-				new_fops = fops_get(c->fops);
-				break;
-			}
+		list_for_each_entry(iter, &misc_list, list) {
+			if (iter->minor != minor)
+				continue;
+			c = iter;
+			new_fops = fops_get(iter->fops);
+			break;
 		}
 		if (!new_fops)
 			goto fail;

base-commit: 34e047aa16c0123bbae8e2f6df33e5ecc1f56601
--
2.25.1