linux-kernel - Re: [PATCH] f2fs: fix to avoid accessing uninitialized field of inode page in is

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Date:   Mon, 9 Sep 2019 16:16:35 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: fix to avoid accessing uninitialized field of inode
 page in is_alive()

On 2019/9/9 15:58, Chao Yu wrote:
> On 2019/9/9 15:44, Jaegeuk Kim wrote:
>> On 09/07, Chao Yu wrote:
>>> On 2019-9-7 7:48, Jaegeuk Kim wrote:
>>>> On 09/06, Chao Yu wrote:
>>>>> If inode is newly created, inode page may not synchronize with inode cache,
>>>>> so fields like .i_inline or .i_extra_isize could be wrong, in below call
>>>>> path, we may access such wrong fields, result in failing to migrate valid
>>>>> target block.
>>>>
>>>> If data is valid, how can we get new inode page?
>>
>> Let me rephrase the question. If inode is newly created, is this data block
>> really valid to move in GC?
> 
> I guess it's valid, let double check that.

We can see inode page:

- f2fs_create
 - f2fs_add_link
  - f2fs_add_dentry
   - f2fs_init_inode_metadata
    - f2fs_add_inline_entry
     - ipage = f2fs_new_inode_page
     - f2fs_put_page(ipage)   <---- after this

> 
>>
>>>
>>> is_alive()
>>> {
>>> ...
>>> 	node_page = f2fs_get_node_page(sbi, nid);  <--- inode page
>>
>> Aren't we seeing the below version warnings?
>>
>> if (sum->version != dni->version) {
>> 	f2fs_warn(sbi, "%s: valid data with mismatched node version.",
>>                            __func__);
>>         set_sbi_flag(sbi, SBI_NEED_FSCK);
>> }

The version of summary and dni are all zero.

summary nid: 613, ofs: 111, ver: 0
blkaddr 2436 (blkaddr in node 0)
expect: seg 10, ofs_in_seg: 54
real: seg 4294967295, ofs_in_seg: 0
ofs: 54, 0
node info ino:613, nid:613, nofs:0
ofs_in_addr: 0

Thanks,

>>
>>>
>>> 	source_blkaddr = datablock_addr(NULL, node_page, ofs_in_node);
>>
>> So, we're getting this? Does this incur infinite loop in GC?
>>
>> if (!test_and_set_bit(segno, SIT_I(sbi)->invalid_segmap)) {
>> 	f2fs_err(sbi, "mismatched blkaddr %u (source_blkaddr %u) in seg %u\n",
>> 	f2fs_bug_on(sbi, 1);
>> }
> 
> Yes, I only get this with generic/269, rather than "valid data with mismatched
> node version.".
> 
> With this patch, generic/269 won't panic again.
> 
> Thanks,
> 
>>
>>> ...
>>> }
>>>
>>> datablock_addr()
>>> {
>>> ...
>>> 	base = offset_in_addr(&raw_node->i);  <--- the base could be wrong here due to
>>> accessing uninitialized .i_inline of raw_node->i.
>>> ...
>>> }
>>>
>>> Thanks,
>>>
>>>>
>>>>>
>>>>> - gc_data_segment
>>>>>  - is_alive
>>>>>   - datablock_addr
>>>>>    - offset_in_addr
>>>>>
>>>>> Fixes: 7a2af766af15 ("f2fs: enhance on-disk inode structure scalability")
>>>>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>>>>> ---
>>>>>  fs/f2fs/dir.c | 3 +++
>>>>>  1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
>>>>> index 765f13354d3f..b1840852967e 100644
>>>>> --- a/fs/f2fs/dir.c
>>>>> +++ b/fs/f2fs/dir.c
>>>>> @@ -479,6 +479,9 @@ struct page *f2fs_init_inode_metadata(struct inode *inode, struct inode *dir,
>>>>>  		if (IS_ERR(page))
>>>>>  			return page;
>>>>>  
>>>>> +		/* synchronize inode page's data from inode cache */
>>>>> +		f2fs_update_inode(inode, page);
>>>>> +
>>>>>  		if (S_ISDIR(inode->i_mode)) {
>>>>>  			/* in order to handle error case */
>>>>>  			get_page(page);
>>>>> -- 
>>>>> 2.18.0.rc1
>> .
>>