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:

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

Link: https://lkml.kernel.org/r/b612a93825e5ea330cb68d2e8b516e9687a06cc6.1605376435.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index 67ff829..7c6b6d8 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -4020,7 +4020,7 @@ out2:
 
 #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,
@@ -4030,16 +4030,19 @@ 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,