[PATCH 1/2 v3] btrfs: label should not contain return char

[Anand Jain <anand.jain@oracle.com>]

From: Anand Jain <Anand.Jain@oracle.com>

generally if you use
  echo "test" > /sys/fs/btrfs/<fsid>/label
it would introduce return char at the end and it can not
be part of the label. The correct command is
  echo -n "test" > /sys/fs/btrfs/<fsid>/label

This patch will check for this user error

Signed-off-by: Anand Jain <Anand.Jain@oracle.com>
---
 v3: accepts review comments. Thanks David and Eric again
 v2: accepts review comments. Thanks Eric and Roman

 fs/btrfs/sysfs.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index c5eb214..159df4f 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -373,8 +373,15 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = fs_info->fs_root;
 	int ret;
+	size_t p_len;
 
-	if (len >= BTRFS_LABEL_SIZE) {
+	/*
+	 * p_len is the len until the first occurrence of either
+	 * '\n' or '\0'
+	 */
+	p_len = strcspn(buf, "\n");
+
+	if (p_len >= BTRFS_LABEL_SIZE) {
 		pr_err("BTRFS: unable to set label with more than %d bytes\n",
 		       BTRFS_LABEL_SIZE - 1);
 		return -EINVAL;
@@ -385,7 +392,8 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 		return PTR_ERR(trans);
 
 	spin_lock(&root->fs_info->super_lock);
-	strcpy(fs_info->super_copy->label, buf);
+	strncpy(fs_info->super_copy->label, buf, p_len);
+	memset(fs_info->super_copy->label + p_len, '\0', 1);
 	spin_unlock(&root->fs_info->super_lock);
 	ret = btrfs_commit_transaction(trans, root);
 
-- 
1.7.1