bcache: fix input overflow to journal_delay_ms

c->journal_delay_ms is in type unsigned short, it is set via sysfs
interface and converted by sysfs_strtoul() from input string to
unsigned short value. Therefore overflow to unsigned short might be
happen when the converted value exceed USHRT_MAX. e.g. writing
65536 into sysfs file journal_delay_ms, c->journal_delay_ms is set to
0.

This patch uses sysfs_strtoul_clamp() to convert the input string and
limit value range in [0, USHRT_MAX], to avoid the input overflow.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/sysfs.c

@@ -821,7 +821,9 @@ STORE(__bch_cache_set)
 		}
 	}
 
-	sysfs_strtoul(journal_delay_ms,		c->journal_delay_ms);
+	sysfs_strtoul_clamp(journal_delay_ms,
+			    c->journal_delay_ms,
+			    0, USHRT_MAX);
 	sysfs_strtoul_bool(verify,		c->verify);
 	sysfs_strtoul_bool(key_merging_disabled, c->key_merging_disabled);
 	sysfs_strtoul(expensive_debug_checks,	c->expensive_debug_checks);