f2fs: add check for deleted inode

The syzbot reproducer mounts a f2fs image, then tries to unlink an
existing file. However, the unlinked file already has a link count of 0
when it is read for the first time in do_read_inode().

Add a check to sanity_check_inode() for i_nlink == 0.

[Chao Yu: rebase the code and fix orphan inode recovery issue]
Reported-by: syzbot+b01a36acd7007e273a83@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b01a36acd7007e273a83
Fixes: 39a53e0ce0df ("f2fs: add superblock and major in-memory structure")
Signed-off-by: Leo Stone <leocstone@gmail.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index a278c7da81778295d46e9b41674e8155b1ff66a2..3d85d8116dae7b62f67f231a8556a0ebbe8de8f9 100644 (file)
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -502,6 +502,14 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
                goto out;
        }
 
+       if (inode->i_nlink == 0) {
+               f2fs_warn(F2FS_I_SB(inode), "%s: inode (ino=%lx) has zero i_nlink",
+                         __func__, inode->i_ino);
+               err = -EFSCORRUPTED;
+               set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
+               goto out_iput;
+       }
+
        if (IS_ENCRYPTED(dir) &&
            (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) &&
            !fscrypt_has_permitted_context(dir, inode)) {