From 1bb30b20b49773369c299d4d6c65227201328663 Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 16 Sep 2021 16:13:42 +0300
Subject: [PATCH] thermal/core: Potential buffer overflow in thermal_build_list_of_policies()
Git-commit: 1bb30b20b49773369c299d4d6c65227201328663
Patch-mainline: v5.15-rc3
References: git-fixes

After printing the list of thermal governors, then this function prints
a newline character.  The problem is that "size" has not been updated
after printing the last governor.  This means that it can write one
character (the NUL terminator) beyond the end of the buffer.

Get rid of the "size" variable and just use "PAGE_SIZE - count" directly.

Fixes: 1b4f48494eb2 ("thermal: core: group functions related to governor handling")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210916131342.GB25094@kili
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/thermal/thermal_core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 97ef9b040b84..51374f4e1cca 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -222,15 +222,14 @@ int thermal_build_list_of_policies(char *buf)
 {
 	struct thermal_governor *pos;
 	ssize_t count = 0;
-	ssize_t size = PAGE_SIZE;
 
 	mutex_lock(&thermal_governor_lock);
 
 	list_for_each_entry(pos, &thermal_governor_list, governor_list) {
-		size = PAGE_SIZE - count;
-		count += scnprintf(buf + count, size, "%s ", pos->name);
+		count += scnprintf(buf + count, PAGE_SIZE - count, "%s ",
+				   pos->name);
 	}
-	count += scnprintf(buf + count, size, "\n");
+	count += scnprintf(buf + count, PAGE_SIZE - count, "\n");
 
 	mutex_unlock(&thermal_governor_lock);
 
-- 
2.26.2