linux-kernel - Re: [PATCH v3] ocfs2: validate inline data i

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Message-ID: <314374af-5b3e-4d34-88c8-4bb2323ad5d5@linux.alibaba.com>
Date: Fri, 12 Dec 2025 13:49:50 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Deepanshu Kartikey <kartikey406@...il.com>, mark@...heh.com,
 jlbec@...lplan.org, heming.zhao@...e.com, akpm <akpm@...ux-foundation.org>
Cc: ocfs2-devel@...ts.linux.dev, linux-kernel@...r.kernel.org,
 syzbot+c897823f699449cc3eb4@...kaller.appspotmail.com
Subject: Re: [PATCH v3] ocfs2: validate inline data i_size during inode read



On 2025/12/12 13:21, Deepanshu Kartikey wrote:
> When reading an inode from disk, ocfs2_validate_inode_block() performs
> various sanity checks but does not validate the size of inline data.
> If the filesystem is corrupted, an inode's i_size can exceed the actual
> inline data capacity (id_count).
> 
> This causes ocfs2_dir_foreach_blk_id() to iterate beyond the inline
> data buffer, triggering a use-after-free when accessing directory
> entries from freed memory.
> 
> In the syzbot report:
>   - i_size was 1099511627576 bytes (~1TB)
>   - Actual inline data capacity (id_count) is typically <256 bytes
>   - A garbage rec_len (54648) caused ctx->pos to jump out of bounds
>   - This triggered a UAF in ocfs2_check_dir_entry()
> 
> Fix by adding a validation check in ocfs2_validate_inode_block() to
> ensure inodes with inline data have i_size <= id_count. This catches
> the corruption early during inode read and prevents all downstream
> code from operating on invalid data.
> 
> Reported-by: syzbot+c897823f699449cc3eb4@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
> Tested-by: syzbot+c897823f699449cc3eb4@...kaller.appspotmail.com
> Link: https://lore.kernel.org/all/20251211115231.3560028-1-kartikey406@gmail.com/T/ [v1]
> Link: https://lore.kernel.org/all/20251212040400.6377-1-kartikey406@gmail.com/T/ [v2]
> Signed-off-by: Deepanshu Kartikey <kartikey406@...il.com>

Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
> ---
> v3:
>   - Folded new check into existing OCFS2_INLINE_DATA_FL block (Joseph Qi)
> 
> v2:
>   - Removed unnecessary S_ISDIR() check since OCFS2_INLINE_DATA_FL
>     applies to both directories and regular files (Heming Zhao)
>   - Fixed checkpatch.pl warnings
> ---
>  fs/ocfs2/inode.c | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 8340525e5589..77f73fa663b7 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1486,12 +1486,25 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  		goto bail;
>  	}
>  
> -	if ((le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) &&
> -	    le32_to_cpu(di->i_clusters)) {
> -		rc = ocfs2_error(sb, "Invalid dinode %llu: %u clusters\n",
> -				 (unsigned long long)bh->b_blocknr,
> -				 le32_to_cpu(di->i_clusters));
> -		goto bail;
> +	if (le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) {
> +		struct ocfs2_inline_data *data = &di->id2.i_data;
> +
> +		if (le32_to_cpu(di->i_clusters)) {
> +			rc = ocfs2_error(sb,
> +					 "Invalid dinode %llu: %u clusters\n",
> +					 (unsigned long long)bh->b_blocknr,
> +					 le32_to_cpu(di->i_clusters));
> +			goto bail;
> +		}
> +
> +		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
> +			rc = ocfs2_error(sb,
> +					 "Invalid dinode #%llu: inline data i_size %llu exceeds id_count %u\n",
> +					 (unsigned long long)bh->b_blocknr,
> +					 (unsigned long long)le64_to_cpu(di->i_size),
> +					 le16_to_cpu(data->id_count));
> +			goto bail;
> +		}
>  	}
>  
>  	if (le32_to_cpu(di->i_flags) & OCFS2_CHAIN_FL) {