f2fs: Add sanity_check_inode() function

This was done as part of commits 5d64600d "f2fs: avoid bug_on on
corrupted inode" and 76d56d4a "f2fs: fix to do sanity check with
extra_attr feature" upstream, but the specific checks they added are
not applicable to 4.4.

Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/f2fs/inode.c

@@ -95,6 +95,13 @@ static void __recover_inline_status(struct inode *inode, struct page *ipage)
 	return;
 }
 
+static bool sanity_check_inode(struct inode *inode)
+{
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+
+	return true;
+}
+
 static int do_read_inode(struct inode *inode)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
@@ -143,6 +150,11 @@ static int do_read_inode(struct inode *inode)
 
 	get_inline_info(fi, ri);
 
+	if (!sanity_check_inode(inode)) {
+		f2fs_put_page(node_page, 1);
+		return -EINVAL;
+	}
+
 	/* check data exist */
 	if (f2fs_has_inline_data(inode) && !f2fs_exist_data(inode))
 		__recover_inline_status(inode, node_page);