zram: use scnprintf() in attrs show() methods

sysfs.txt documentation lists the following requirements:

 - The buffer will always be PAGE_SIZE bytes in length. On i386, this
   is 4096.

 - show() methods should return the number of bytes printed into the
   buffer. This is the return value of scnprintf().

 - show() should always use scnprintf().

Use scnprintf() in show() functions.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/zram/zcomp.c

@@ -275,12 +275,14 @@ ssize_t zcomp_available_show(const char *comp, char *buf)
 
 	while (backends[i]) {
 		if (sysfs_streq(comp, backends[i]->name))
-			sz += sprintf(buf + sz, "[%s] ", backends[i]->name);
+			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
+					"[%s] ", backends[i]->name);
 		else
-			sz += sprintf(buf + sz, "%s ", backends[i]->name);
+			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
+					"%s ", backends[i]->name);
 		i++;
 	}
-	sz += sprintf(buf + sz, "\n");
+	sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");
 	return sz;
 }
 

drivers/block/zram/zram_drv.c

@@ -48,7 +48,7 @@ static ssize_t zram_attr_##name##_show(struct device *d,		\
 				struct device_attribute *attr, char *b)	\
 {									\
 	struct zram *zram = dev_to_zram(d);				\
-	return sprintf(b, "%llu\n",					\
+	return scnprintf(b, PAGE_SIZE, "%llu\n",			\
 		(u64)atomic64_read(&zram->stats.name));			\
 }									\
 static struct device_attribute dev_attr_##name =			\
@@ -69,7 +69,7 @@ static ssize_t disksize_show(struct device *dev,
 {
 	struct zram *zram = dev_to_zram(dev);
 
-	return sprintf(buf, "%llu\n", zram->disksize);
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
 }
 
 static ssize_t initstate_show(struct device *dev,
@@ -82,7 +82,7 @@ static ssize_t initstate_show(struct device *dev,
 	val = init_done(zram);
 	up_read(&zram->init_lock);
 
-	return sprintf(buf, "%u\n", val);
+	return scnprintf(buf, PAGE_SIZE, "%u\n", val);
 }
 
 static ssize_t orig_data_size_show(struct device *dev,
@@ -90,7 +90,7 @@ static ssize_t orig_data_size_show(struct device *dev,
 {
 	struct zram *zram = dev_to_zram(dev);
 
-	return sprintf(buf, "%llu\n",
+	return scnprintf(buf, PAGE_SIZE, "%llu\n",
 		(u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
 }
 
@@ -106,7 +106,7 @@ static ssize_t mem_used_total_show(struct device *dev,
 		val = zs_get_total_size_bytes(meta->mem_pool);
 	up_read(&zram->init_lock);
 
-	return sprintf(buf, "%llu\n", val);
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
 }
 
 static ssize_t max_comp_streams_show(struct device *dev,
@@ -119,7 +119,7 @@ static ssize_t max_comp_streams_show(struct device *dev,
 	val = zram->max_comp_streams;
 	up_read(&zram->init_lock);
 
-	return sprintf(buf, "%d\n", val);
+	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
 }
 
 static ssize_t max_comp_streams_store(struct device *dev,