Re: [PATCH v4] f2fs: add check for deleted inode

[Chao Yu <chao@kernel.org>]

On 2025/2/27 1:15, Jaegeuk Kim wrote:
> On 02/26, Chao Yu wrote:
>> On 2/26/25 11:28, Jaegeuk Kim wrote:
>>> On 02/24, Chao Yu wrote:
>>>> On 2/14/25 09:44, Chao Yu wrote:
>>>>> On 2/14/25 01:38, Jaegeuk Kim wrote:
>>>>>> On 02/13, Chao Yu wrote:
>>>>>>> On 2/13/25 00:47, Jaegeuk Kim wrote:
>>>>>>>> On 02/12, Chao Yu wrote:
>>>>>>>>> From: Leo Stone <leocstone@gmail.com>
>>>>>>>>>
>>>>>>>>> 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>
>>>>>>>>> ---
>>>>>>>>>   fs/f2fs/checkpoint.c | 4 ++++
>>>>>>>>>   fs/f2fs/f2fs.h       | 1 +
>>>>>>>>>   fs/f2fs/inode.c      | 6 ++++++
>>>>>>>>>   3 files changed, 11 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>>>>>>> index bd890738b94d..ada2c548645c 100644
>>>>>>>>> --- a/fs/f2fs/checkpoint.c
>>>>>>>>> +++ b/fs/f2fs/checkpoint.c
>>>>>>>>> @@ -751,6 +751,8 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
>>>>>>>>>   	if (is_sbi_flag_set(sbi, SBI_IS_WRITABLE))
>>>>>>>>>   		f2fs_info(sbi, "orphan cleanup on readonly fs");
>>>>>>>>>   
>>>>>>>>> +	set_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
>>>>>>>>
>>>>>>>> What about using SBI_POR_DOING?
>>>>>>>
>>>>>>> SBI_POR_DOING will cover most flow of f2fs_fill_super(), I think we can add a
>>>>>>> separated flag just covering f2fs_recover_orphan_inodes(), so that we can allow
>>>>>>> iget() of root_inode and all inodes during roll-forward recovery to do sanity
>>>>>>> check nlink w/ zero. What do you think?
>>>>>>
>>>>>> Can we do this sanity check after f2fs_iget in the f2fs_unlink() only?
>>>>>
>>>>> Sure, we need to cover f2fs_rename() as well, please check this:
>>>>>
>>>>> https://lore.kernel.org/all/67450f9a.050a0220.21d33d.0003.GAE@google.com
>>>>
>>>> Hi Jaegeuk,
>>>>
>>>> I'm testing this, seems there is a problem, once we opened an inode that
>>>> has zeroed nlink, in f2fs_evict_inode(), the inode and all its data will be
>>>> deleted, then leaving its stale dir entry in parent directory.
>>>>
>>>> What do you think using v4? so that we may has chance to repair it w/ fsck
>>>> rather than just deleting it?
>>>
>>> Do you mean v4 as the below change?
>>
>> I mean this v4 patch:
> 
> What about checking i_nlink right after f2fs_iget in f2fs_lookup?

Fine to me, I've updated in v5.

Thanks,

> 
>>
>> ---
>>   fs/f2fs/checkpoint.c | 4 ++++
>>   fs/f2fs/f2fs.h       | 1 +
>>   fs/f2fs/inode.c      | 6 ++++++
>>   3 files changed, 11 insertions(+)
>>
>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>> index bd890738b94d..ada2c548645c 100644
>> --- a/fs/f2fs/checkpoint.c
>> +++ b/fs/f2fs/checkpoint.c
>> @@ -751,6 +751,8 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
>>   	if (is_sbi_flag_set(sbi, SBI_IS_WRITABLE))
>>   		f2fs_info(sbi, "orphan cleanup on readonly fs");
>>
>> +	set_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
>> +
>>   	start_blk = __start_cp_addr(sbi) + 1 + __cp_payload(sbi);
>>   	orphan_blocks = __start_sum_addr(sbi) - 1 - __cp_payload(sbi);
>>
>> @@ -778,9 +780,11 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
>>   		}
>>   		f2fs_put_page(page, 1);
>>   	}
>> +
>>   	/* clear Orphan Flag */
>>   	clear_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
>>   out:
>> +	clear_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
>>   	set_sbi_flag(sbi, SBI_IS_RECOVERED);
>>
>>   	return err;
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 05879c6dc4d6..1c75081c0c14 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -1322,6 +1322,7 @@ enum {
>>   	SBI_IS_CLOSE,				/* specify unmounting */
>>   	SBI_NEED_FSCK,				/* need fsck.f2fs to fix */
>>   	SBI_POR_DOING,				/* recovery is doing or not */
>> +	SBI_ORPHAN_RECOVERY,			/* orphan inodes recovery is doing */
>>   	SBI_NEED_SB_WRITE,			/* need to recover superblock */
>>   	SBI_NEED_CP,				/* need to checkpoint */
>>   	SBI_IS_SHUTDOWN,			/* shutdown by ioctl */
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>> index d6ad7810df69..02f1b69d03d8 100644
>> --- a/fs/f2fs/inode.c
>> +++ b/fs/f2fs/inode.c
>> @@ -386,6 +386,12 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
>>   		}
>>   	}
>>
>> +	if (inode->i_nlink == 0 && !is_sbi_flag_set(sbi, SBI_ORPHAN_RECOVERY)) {
>> +		f2fs_warn(sbi, "%s: inode (ino=%lx) has a link count of 0",
>> +			  __func__, inode->i_ino);
>> +		return false;
>> +	}
>> +
>>   	return true;
>>   }
>>
>> Thanks,
>>
>>>
>>>>
>>>> ---
>>>>   fs/f2fs/namei.c | 19 +++++++++++++++++++
>>>>   1 file changed, 19 insertions(+)
>>>>
>>>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
>>>> index a278c7da8177..949621bc0d07 100644
>>>> --- a/fs/f2fs/namei.c
>>>> +++ b/fs/f2fs/namei.c
>>>> @@ -547,6 +547,16 @@ static int f2fs_unlink(struct inode *dir, struct dentry *dentry)
>>>>   		goto fail;
>>>>   	}
>>>>
>>>> +	if (unlikely(S_ISDIR(inode->i_mode) ?
>>>> +			inode->i_nlink <= 1 : inode->i_nlink == 0)) {
>>>> +		f2fs_err_ratelimited(sbi, "%s: inode (ino=%lx) has inconsistent nlink: %u, isdir: %d",
>>>> +				__func__, inode->i_ino, inode->i_nlink,
>>>> +				S_ISDIR(inode->i_mode));
>>>> +		err = -EFSCORRUPTED;
>>>> +		set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>> +		goto fail;
>>>> +	}
>>>> +
>>>>   	err = f2fs_dquot_initialize(dir);
>>>>   	if (err)
>>>>   		goto fail;
>>>> @@ -968,6 +978,15 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
>>>>   	}
>>>>
>>>>   	if (new_inode) {
>>>> +		if (unlikely(old_is_dir ?
>>>> +			new_inode->i_nlink <= 1 : new_inode->i_nlink == 0)) {
>>>> +			f2fs_err_ratelimited(sbi, "%s: inode (ino=%lx) has inconsistent nlink: %u, isdir: %d",
>>>> +				__func__, new_inode->i_ino, new_inode->i_nlink,
>>>> +				S_ISDIR(new_inode->i_mode));
>>>> +			err = -EFSCORRUPTED;
>>>> +			set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>> +			goto out_dir;
>>>> +		}
>>>>
>>>>   		err = -ENOTEMPTY;
>>>>   		if (old_is_dir && !f2fs_empty_dir(new_inode))
>>>> -- 
>>>> 2.48.1.601.g30ceb7b040-goog
>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>>>
>>>>>>>>> +
>>>>>>>>>   	start_blk = __start_cp_addr(sbi) + 1 + __cp_payload(sbi);
>>>>>>>>>   	orphan_blocks = __start_sum_addr(sbi) - 1 - __cp_payload(sbi);
>>>>>>>>>   
>>>>>>>>> @@ -778,9 +780,11 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
>>>>>>>>>   		}
>>>>>>>>>   		f2fs_put_page(page, 1);
>>>>>>>>>   	}
>>>>>>>>> +
>>>>>>>>>   	/* clear Orphan Flag */
>>>>>>>>>   	clear_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
>>>>>>>>>   out:
>>>>>>>>> +	clear_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
>>>>>>>>>   	set_sbi_flag(sbi, SBI_IS_RECOVERED);
>>>>>>>>>   
>>>>>>>>>   	return err;
>>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>>>> index 05879c6dc4d6..1c75081c0c14 100644
>>>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>>>> @@ -1322,6 +1322,7 @@ enum {
>>>>>>>>>   	SBI_IS_CLOSE,				/* specify unmounting */
>>>>>>>>>   	SBI_NEED_FSCK,				/* need fsck.f2fs to fix */
>>>>>>>>>   	SBI_POR_DOING,				/* recovery is doing or not */
>>>>>>>>> +	SBI_ORPHAN_RECOVERY,			/* orphan inodes recovery is doing */
>>>>>>>>>   	SBI_NEED_SB_WRITE,			/* need to recover superblock */
>>>>>>>>>   	SBI_NEED_CP,				/* need to checkpoint */
>>>>>>>>>   	SBI_IS_SHUTDOWN,			/* shutdown by ioctl */
>>>>>>>>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>>>>>>>>> index d6ad7810df69..02f1b69d03d8 100644
>>>>>>>>> --- a/fs/f2fs/inode.c
>>>>>>>>> +++ b/fs/f2fs/inode.c
>>>>>>>>> @@ -386,6 +386,12 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
>>>>>>>>>   		}
>>>>>>>>>   	}
>>>>>>>>>   
>>>>>>>>> +	if (inode->i_nlink == 0 && !is_sbi_flag_set(sbi, SBI_ORPHAN_RECOVERY)) {
>>>>>>>>> +		f2fs_warn(sbi, "%s: inode (ino=%lx) has a link count of 0",
>>>>>>>>> +			  __func__, inode->i_ino);
>>>>>>>>> +		return false;
>>>>>>>>> +	}
>>>>>>>>> +
>>>>>>>>>   	return true;
>>>>>>>>>   }
>>>>>>>>>   
>>>>>>>>> -- 
>>>>>>>>> 2.48.1.502.g6dc24dfdaf-goog
>>>>>