f2fs: fix to detect corrupted meta ino

It is possible that ino of dirent or orphan inode is corrupted in a
fuzzed image, occasionally, if corrupted ino is equal to meta ino:
meta_ino, node_ino or compress_ino, caller of f2fs_iget() from below
call paths will get meta inode directly, it's not allowed, let's
add sanity check to detect such cases.

case #1
- recover_dentry
 - __f2fs_find_entry
 - f2fs_iget_retry

case #2
- recover_orphan_inode
 - f2fs_iget_retry

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/inode.c

@@ -487,6 +487,12 @@ static int do_read_inode(struct inode *inode)
 	return 0;
 }
 
+static bool is_meta_ino(struct f2fs_sb_info *sbi, unsigned int ino)
+{
+	return ino == F2FS_NODE_INO(sbi) || ino == F2FS_META_INO(sbi) ||
+		ino == F2FS_COMPRESS_INO(sbi);
+}
+
 struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
@@ -498,16 +504,21 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
 		return ERR_PTR(-ENOMEM);
 
 	if (!(inode->i_state & I_NEW)) {
+		if (is_meta_ino(sbi, ino)) {
+			f2fs_err(sbi, "inaccessible inode: %lu, run fsck to repair", ino);
+			set_sbi_flag(sbi, SBI_NEED_FSCK);
+			ret = -EFSCORRUPTED;
+			trace_f2fs_iget_exit(inode, ret);
+			iput(inode);
+			return ERR_PTR(ret);
+		}
+
 		trace_f2fs_iget(inode);
 		return inode;
 	}
-	if (ino == F2FS_NODE_INO(sbi) || ino == F2FS_META_INO(sbi))
-		goto make_now;
 
-#ifdef CONFIG_F2FS_FS_COMPRESSION
-	if (ino == F2FS_COMPRESS_INO(sbi))
+	if (is_meta_ino(sbi, ino))
 		goto make_now;
-#endif
 
 	ret = do_read_inode(inode);
 	if (ret)