linux-kernel - [PATCH] test_firmware: fix end of loop test in upload_read

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Date:   Thu, 5 May 2022 13:29:15 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russ Weight <russell.h.weight@...el.com>
Cc:     Tianfei zhang <tianfei.zhang@...el.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Shawn Guo <shawn.guo@...aro.org>, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] test_firmware: fix end of loop test in upload_read_show()

If we iterate through a loop using list_for_each_entry() without
hitting a break, then the iterator points to bogus memory.  The
if (tst->name != test_fw_config->upload_name) { will likely still work
but technically it's an out of bounds read.

Fixes: a31ad463b72d ("test_firmware: Add test support for firmware upload")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 lib/test_firmware.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/lib/test_firmware.c b/lib/test_firmware.c
index 76115c1a2629..c82b65947ce6 100644
--- a/lib/test_firmware.c
+++ b/lib/test_firmware.c
@@ -1392,7 +1392,8 @@ static ssize_t upload_read_show(struct device *dev,
 				struct device_attribute *attr,
 				char *buf)
 {
-	struct test_firmware_upload *tst;
+	struct test_firmware_upload *tst = NULL;
+	struct test_firmware_upload *tst_iter;
 	int ret = -EINVAL;
 
 	if (!test_fw_config->upload_name) {
@@ -1401,11 +1402,13 @@ static ssize_t upload_read_show(struct device *dev,
 	}
 
 	mutex_lock(&test_fw_mutex);
-	list_for_each_entry(tst, &test_upload_list, node)
-		if (tst->name == test_fw_config->upload_name)
+	list_for_each_entry(tst_iter, &test_upload_list, node)
+		if (tst_iter->name == test_fw_config->upload_name) {
+			tst = tst_iter;
 			break;
+		}
 
-	if (tst->name != test_fw_config->upload_name) {
+	if (!tst) {
 		pr_err("Firmware name not found: %s\n",
 		       test_fw_config->upload_name);
 		goto out;
-- 
2.35.1