linux-kernel - Re: [PATCH V3] ocfs2: add a sanity check for i

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Message-ID: <tencent_A6B4645A17675769C6D6F37A8362C9660305@qq.com>
Date: Wed, 16 Oct 2024 19:57:36 +0800
From: Edward Adam Davis <eadavis@...com>
To: joseph.qi@...ux.alibaba.com
Cc: eadavis@...com,
	jlbec@...lplan.org,
	linux-kernel@...r.kernel.org,
	mark@...heh.com,
	ocfs2-devel@...ts.linux.dev,
	syzbot+797d4829dafe3f11dce7@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V3] ocfs2: add a sanity check for i_size

On Wed, 16 Oct 2024 19:08:26 +0800, Joseph Qi wrote:
> On 10/16/24 11:52 AM, Edward Adam Davis wrote:
> > On Wed, 16 Oct 2024 10:06:27 +0800, Joseph Qi wrote:
> >>> Reported-and-tested-by: syzbot+797d4829dafe3f11dce7@...kaller.appspotmail.com
> >>> Closes: https://syzkaller.appspot.com/bug?extid=797d4829dafe3f11dce7
> >>> Signed-off-by: Edward Adam Davis <eadavis@...com>
> >>> ---
> >>> V1 -> V2: keep rc to 0 when falgs contains READHEAD
> >>> V2 -> V3: check i_size only and alert subject and comments
> >>>
> >>>  fs/ocfs2/extent_map.c | 6 +++++-
> >>>  1 file changed, 5 insertions(+), 1 deletion(-)
> >>>
> >>> #syz test
> >>>
> >>> diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
> >>> index f7672472fa82..29d27a70dbdd 100644
> >>> --- a/fs/ocfs2/extent_map.c
> >>> +++ b/fs/ocfs2/extent_map.c
> >>> @@ -961,13 +961,17 @@ int ocfs2_read_virt_blocks(struct inode *inode, u64 v_block, int nr,
> >>>  	int rc = 0;
> >>>  	u64 p_block, p_count;
> >>>  	int i, count, done = 0;
> >>> +	loff_t i_size = i_size_read(inode);
> >>>
> >>>  	trace_ocfs2_read_virt_blocks(
> >>>  	     inode, (unsigned long long)v_block, nr, bhs, flags,
> >>>  	     validate);
> >>>
> >>> +	if (!i_size)
> >>> +		return -EINVAL;
> >>> +
> >>
> >> Take a more consideration, inode size 0 doesn't mean it has no blocks,
> >> since we have a case that fallocate with KEEP_SIZE.
> >> Could you please check inode->i_blocks in above coredump?
> > I have previously verified the value of inode->i_blocks in my testing environment, which is 0.
> >
> So it seems the check condition should be:
> 
>   (v_block + nr) > (inode->i_blocks >> (inode->i_sb->s_blocksize_bits - 9))
Do you mean like this?

diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index f7672472fa82..9613cd356ac5 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -966,6 +966,9 @@ int ocfs2_read_virt_blocks(struct inode *inode, u64 v_block, int nr,
             inode, (unsigned long long)v_block, nr, bhs, flags,
             validate);

+       if ((v_block + nr) > (inode->i_blocks >> (inode->i_sb->s_blocksize_bits - 9)))
+               return -EINVAL;
+
        if (((v_block + nr - 1) << inode->i_sb->s_blocksize_bits) >=
            i_size_read(inode)) {
                BUG_ON(!(flags & OCFS2_BH_READAHEAD));

BR,
Edward