linux-kernel - Re: [PATCH V3 2/2] ocfs2: Fix uaf in ocfs2_set_buffer

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Message-ID: <7da687ce-ffb7-44e3-bddc-d5c2f4f48c95@linux.alibaba.com>
Date: Wed, 21 Aug 2024 08:08:44 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Lizhi Xu <lizhi.xu@...driver.com>, heming.zhao@...e.com
Cc: jlbec@...lplan.org, linux-kernel@...r.kernel.org, mark@...heh.com,
 ocfs2-devel@...ts.linux.dev,
 syzbot+ab134185af9ef88dfed5@...kaller.appspotmail.com,
 syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V3 2/2] ocfs2: Fix uaf in ocfs2_set_buffer_uptodate



On 8/20/24 5:45 PM, Lizhi Xu wrote:
> In the for-loop after the 'read_failure' label, the condition
> '(bh == NULL) && flags includes OCFS2_BH_READAHEAD' is missing.
> When this contidion is true, this for-loop will call ocfs2_set_buffer
> _uptodate(ci, bh), which then triggers a NULL pointer access error.
> 

Or it may simplified as the following:

When doing cleanup, if flags without OCFS2_BH_READAHEAD, it may trigger
NULL pointer dereference in the following ocfs2_set_buffer_uptodate() if
bh is NULL.

> Changes from V2:
> * Make the code more concise
> 

This is not the right place for changelog.

Thanks,
Joseph

> Reported-and-suggested-by: Heming Zhao <heming.zhao@...e.com>
> Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
> Reviewed-by: Heming Zhao <heming.zhao@...e.com>
> ---
>  fs/ocfs2/buffer_head_io.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
> index e62c7e1de4eb..8f714406528d 100644
> --- a/fs/ocfs2/buffer_head_io.c
> +++ b/fs/ocfs2/buffer_head_io.c
> @@ -388,7 +388,8 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 block, int nr,
>  		/* Always set the buffer in the cache, even if it was
>  		 * a forced read, or read-ahead which hasn't yet
>  		 * completed. */
> -		ocfs2_set_buffer_uptodate(ci, bh);
> +		if (bh)
> +			ocfs2_set_buffer_uptodate(ci, bh);
>  	}
>  	ocfs2_metadata_cache_io_unlock(ci);
>