linux-kernel - Re: [PATCH V2] ocfs2: pass u64 to ocfs2_truncate

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Message-ID: <ed4no1gp.fsf@damenly.org>
Date: Fri, 11 Oct 2024 09:07:09 +0800
From: Su Yue <l@...enly.org>
To: Edward Adam Davis <eadavis@...com>
Cc: joseph.qi@...ux.alibaba.com, jlbec@...lplan.org,
 linux-kernel@...r.kernel.org, mark@...heh.com,
 ocfs2-devel@...ts.linux.dev,
 syzbot+81092778aac03460d6b7@...kaller.appspotmail.com,
 syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V2] ocfs2: pass u64 to ocfs2_truncate_inline maybe overflow


On Thu 10 Oct 2024 at 22:31, Edward Adam Davis <eadavis@...com> 
wrote:

> Syzbot reported a kernel BUG in ocfs2_truncate_inline.
> There are two reasons for this: first, the parameter value 
> passed is greater
> than UINT_MAX, second, the start and end parameters of 
> ocfs2_truncate_inline
> are "unsigned int".
>
> So, we need to add a sanity check for byte_start and byte_len 
> right before
> ocfs2_truncate_inline() in ocfs2_remove_inode_range(), if they 
> are greater
> than UINT_MAX return -EFBIG.
>
> Reported-by: 
> syzbot+81092778aac03460d6b7@...kaller.appspotmail.com
> Closes: 
> https://syzkaller.appspot.com/bug?extid=81092778aac03460d6b7
> Signed-off-by: Edward Adam Davis <eadavis@...com>
> ---
> V1 -> V2: move sanity check to ocfs2_remove_inode_range
>
>  fs/ocfs2/file.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index ad131a2fc58e..05d6a8acfcda 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -1784,6 +1784,11 @@ int ocfs2_remove_inode_range(struct inode 
> *inode,
>  		return 0;
>
>  	if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
> +		if (byte_start > UINT_MAX || byte_start + byte_len > 
> UINT_MAX) {
>
Why not use ocfs2_max_inline_data_with_xattr() here? Yes, UINT_MAX 
indeed
solves overflow problem Syzbot reported but you can find much 
lowerer
limit if once looked into inline data structures.
Also, ocfs2_truncate_inline() can be enhanced e.g. replace
BUG_ON(start > end) with error out.

--
Su


> +			ret = -EFBIG;
> +			mlog_errno(ret);
> +			goto out;
> +		}
>  		ret = ocfs2_truncate_inline(inode, di_bh, byte_start,
>  					    byte_start + byte_len, 0);
>  		if (ret) {