linux-kernel - [PATCH V2 4/5] mm: shmem: Convert shmem_enabled_show to use sysfs_emit

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Message-Id: <b612a93825e5ea330cb68d2e8b516e9687a06cc6.1605376435.git.joe@perches.com>
Date:   Sat, 14 Nov 2020 10:50:25 -0800
From:   Joe Perches <joe@...ches.com>
To:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH V2 4/5] mm: shmem: Convert shmem_enabled_show to use sysfs_emit_at

Update the function to use sysfs_emit_at while neatening the uses of
sprintf and overwriting the last space char with a newline to avoid
possible output buffer overflow.

Miscellanea:

o in shmem_enabled_show, the removal of the indirected use of fmt
  allows __printf verification

Signed-off-by: Joe Perches <joe@...ches.com>
---
 mm/shmem.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 028f4596fc16..48bafe10c6c2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -4047,7 +4047,7 @@ int __init shmem_init(void)
 
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
 static ssize_t shmem_enabled_show(struct kobject *kobj,
-		struct kobj_attribute *attr, char *buf)
+				  struct kobj_attribute *attr, char *buf)
 {
 	static const int values[] = {
 		SHMEM_HUGE_ALWAYS,
@@ -4057,16 +4057,19 @@ static ssize_t shmem_enabled_show(struct kobject *kobj,
 		SHMEM_HUGE_DENY,
 		SHMEM_HUGE_FORCE,
 	};
-	int i, count;
-
-	for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
-		const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
+	int len = 0;
+	int i;
 
-		count += sprintf(buf + count, fmt,
-				shmem_format_huge(values[i]));
+	for (i = 0; i < ARRAY_SIZE(values); i++) {
+		len += sysfs_emit_at(buf, len,
+				     shmem_huge == values[i] ? "%s[%s]" : "%s%s",
+				     i ? " " : "",
+				     shmem_format_huge(values[i]));
 	}
-	buf[count - 1] = '\n';
-	return count;
+
+	len += sysfs_emit_at(buf, len, "\n");
+
+	return len;
 }
 
 static ssize_t shmem_enabled_store(struct kobject *kobj,
-- 
2.26.0