btrfs: sysfs: validate scrub_speed_max value

The value set as scrub_speed_max accepts size with suffixes
(k/m/g/t/p/e) but we should still validate it for trailing characters,
similar to what we do with chunk_size_store.

CC: stable@vger.kernel.org # 5.15+
Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/sysfs.c

@@ -1783,6 +1783,10 @@ static ssize_t btrfs_devinfo_scrub_speed_max_store(struct kobject *kobj,
 	unsigned long long limit;
 
 	limit = memparse(buf, &endptr);
+	/* There could be trailing '\n', also catch any typos after the value. */
+	endptr = skip_spaces(endptr);
+	if (*endptr != 0)
+		return -EINVAL;
 	WRITE_ONCE(device->scrub_speed_max, limit);
 	return len;
 }