From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 11 Mar 2020 08:08:51 +0100
Subject: ACPI: fan: Use scnprintf() for avoiding potential buffer overflow
Patch-mainline: v5.7-rc1
Git-commit: 949fe25f2ad31f72572dcad491843d355dc93b32
References: jsc#SLE-16407

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().

Also adjust the argument to really match with the actually remaining
buffer size.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 drivers/acpi/fan.c |   20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

--- a/drivers/acpi/fan.c
+++ b/drivers/acpi/fan.c
@@ -276,29 +276,29 @@ static ssize_t show_state(struct device
 	int count;
 
 	if (fps->control == 0xFFFFFFFF || fps->control > 100)
-		count = snprintf(buf, PAGE_SIZE, "not-defined:");
+		count = scnprintf(buf, PAGE_SIZE, "not-defined:");
 	else
-		count = snprintf(buf, PAGE_SIZE, "%lld:", fps->control);
+		count = scnprintf(buf, PAGE_SIZE, "%lld:", fps->control);
 
 	if (fps->trip_point == 0xFFFFFFFF || fps->trip_point > 9)
-		count += snprintf(&buf[count], PAGE_SIZE, "not-defined:");
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "not-defined:");
 	else
-		count += snprintf(&buf[count], PAGE_SIZE, "%lld:", fps->trip_point);
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "%lld:", fps->trip_point);
 
 	if (fps->speed == 0xFFFFFFFF)
-		count += snprintf(&buf[count], PAGE_SIZE, "not-defined:");
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "not-defined:");
 	else
-		count += snprintf(&buf[count], PAGE_SIZE, "%lld:", fps->speed);
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "%lld:", fps->speed);
 
 	if (fps->noise_level == 0xFFFFFFFF)
-		count += snprintf(&buf[count], PAGE_SIZE, "not-defined:");
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "not-defined:");
 	else
-		count += snprintf(&buf[count], PAGE_SIZE, "%lld:", fps->noise_level * 100);
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "%lld:", fps->noise_level * 100);
 
 	if (fps->power == 0xFFFFFFFF)
-		count += snprintf(&buf[count], PAGE_SIZE, "not-defined\n");
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "not-defined\n");
 	else
-		count += snprintf(&buf[count], PAGE_SIZE, "%lld\n", fps->power);
+		count += scnprintf(&buf[count], PAGE_SIZE - count, "%lld\n", fps->power);
 
 	return count;
 }