linux-kernel - [PATCH] drivers/base/cpu: Use scnprintf() for avoiding potential buffer overflow

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Message-Id: <20200311071200.4024-1-tiwai@suse.de>
Date:   Wed, 11 Mar 2020 08:12:00 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] drivers/base/cpu: Use scnprintf() for avoiding potential buffer overflow

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().

Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 drivers/base/cpu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 6265871a4af2..0abcd9d68714 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -231,7 +231,7 @@ static struct cpu_attr cpu_attrs[] = {
 static ssize_t print_cpus_kernel_max(struct device *dev,
 				     struct device_attribute *attr, char *buf)
 {
-	int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
+	int n = scnprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 	return n;
 }
 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
@@ -258,13 +258,13 @@ static ssize_t print_cpus_offline(struct device *dev,
 			buf[n++] = ',';
 
 		if (nr_cpu_ids == total_cpus-1)
-			n += snprintf(&buf[n], len - n, "%u", nr_cpu_ids);
+			n += scnprintf(&buf[n], len - n, "%u", nr_cpu_ids);
 		else
-			n += snprintf(&buf[n], len - n, "%u-%d",
+			n += scnprintf(&buf[n], len - n, "%u-%d",
 						      nr_cpu_ids, total_cpus-1);
 	}
 
-	n += snprintf(&buf[n], len - n, "\n");
+	n += scnprintf(&buf[n], len - n, "\n");
 	return n;
 }
 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
-- 
2.16.4