xfs: revert commit 8954c44

The name passed into __xfs_xattr_put_listent is exactly namelen bytes
long and not null-terminated.  Passing namelen+1 to the strscpy function

    strscpy(offset, (char *)name, namelen + 1);

is therefore wrong.  Go back to the old code, which works fine because
strncpy won't find a null in @name and stops after namelen bytes.  It
really could be a memcpy call, but it worked for years.

Reported-by: syzbot+898115bc6d7140437215@syzkaller.appspotmail.com
Fixes: 8954c44 ("xfs: use strscpy() to instead of strncpy()")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/xfs_xattr.c

@@ -212,7 +212,9 @@ __xfs_xattr_put_listent(
 	offset = context->buffer + context->count;
 	memcpy(offset, prefix, prefix_len);
 	offset += prefix_len;
-	strscpy(offset, (char *)name, namelen + 1);			/* real name */
+	strncpy(offset, (char *)name, namelen);			/* real name */
+	offset += namelen;
+	*offset = '\0';
 
 compute_size:
 	context->count += prefix_len + namelen + 1;