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 09:37:25 +0100
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     Chao Yu <chao@...nel.org>, 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 09/09, Chao Yu wrote:
> 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

Can you print out how many block was assigned to this inode?

> 
> > 
> >>
> >>>
> >>> 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.

Then, this node was allocated and removed without being flushed.

> 
> 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.".

Was this block moved as valid? In either way, is_alive() returns false, no?
How about checking i_blocks to detect the page is initialized in is_alive()?

> > 
> > 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
> >> .
> >>