f2fs: fix to adapt small inline xattr space in __find_inline_xattr()

With below testcase, we will fail to find existed xattr entry:

1. mkfs.f2fs -O extra_attr -O flexible_inline_xattr /dev/zram0
2. mount -t f2fs -o inline_xattr_size=1 /dev/zram0 /mnt/f2fs/
3. touch /mnt/f2fs/file
4. setfattr -n "user.name" -v 0 /mnt/f2fs/file
5. getfattr -n "user.name" /mnt/f2fs/file

/mnt/f2fs/file: user.name: No such attribute

The reason is for inode which has very small inline xattr size,
__find_inline_xattr() will fail to traverse any entry due to first
entry may not be loaded from xattr node yet, later, we may skip to
check entire xattr datas in __find_xattr(), result in such wrong
condition.

This patch adds condition to check such case to avoid this issue.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/xattr.c

@@ -224,11 +224,11 @@ static struct f2fs_xattr_entry *__find_inline_xattr(struct inode *inode,
 {
 	struct f2fs_xattr_entry *entry;
 	unsigned int inline_size = inline_xattr_size(inode);
+	void *max_addr = base_addr + inline_size;
 
 	list_for_each_xattr(entry, base_addr) {
-		if ((void *)entry + sizeof(__u32) > base_addr + inline_size ||
-			(void *)XATTR_NEXT_ENTRY(entry) + sizeof(__u32) >
-			base_addr + inline_size) {
+		if ((void *)entry + sizeof(__u32) > max_addr ||
+			(void *)XATTR_NEXT_ENTRY(entry) > max_addr) {
 			*last_addr = entry;
 			return NULL;
 		}
@@ -239,6 +239,13 @@ static struct f2fs_xattr_entry *__find_inline_xattr(struct inode *inode,
 		if (!memcmp(entry->e_name, name, len))
 			break;
 	}
+
+	/* inline xattr header or entry across max inline xattr size */
+	if (IS_XATTR_LAST_ENTRY(entry) &&
+		(void *)entry + sizeof(__u32) > max_addr) {
+		*last_addr = entry;
+		return NULL;
+	}
 	return entry;
 }