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 08:44:25 +0100
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     Chao Yu <yuchao0@...wei.com>,
        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 09/07, 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?

> 
> 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);
}

> 
> 	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);
}

> ...
> }
> 
> 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