bcache: fix input overflow to cache set io_error_limit

c->error_limit is in type unsigned int, it is set via cache set sysfs
file io_error_limit. Inside the bcache code, input string is converted
by strtoul_or_return() and set the converted value to c->error_limit.

Because the converted value is unsigned long, and c->error_limit is
unsigned int, if the input is large enought, overflow will happen to
c->error_limit.

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

drivers/md/bcache/sysfs.c

@@ -801,8 +801,7 @@ STORE(__bch_cache_set)
 		c->on_error = v;
 	}
 
-	if (attr == &sysfs_io_error_limit)
-		c->error_limit = strtoul_or_return(buf);
+	sysfs_strtoul_clamp(io_error_limit, c->error_limit, 0, UINT_MAX);
 
 	/* See count_io_errors() for why 88 */
 	if (attr == &sysfs_io_error_halflife)