linux-kernel - Re: [PATCH V2 2/2] ocfs2: Fix uaf in ocfs2_read

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Message-ID: <2d6499d6-fd03-43d8-9595-5babfd82481d@suse.com>
Date: Tue, 20 Aug 2024 15:15:26 +0800
From: Heming Zhao <heming.zhao@...e.com>
To: Lizhi Xu <lizhi.xu@...driver.com>
Cc: jlbec@...lplan.org, joseph.qi@...ux.alibaba.com,
 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 V2 2/2] ocfs2: Fix uaf in ocfs2_read_blocks

On 8/20/24 14:55, 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.
> 
> Reported-and-suggested-by: Heming Zhao <heming.zhao@...e.com>
> Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
> ---
>   fs/ocfs2/buffer_head_io.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
> index e62c7e1de4eb..b4a76f45253d 100644
> --- a/fs/ocfs2/buffer_head_io.c
> +++ b/fs/ocfs2/buffer_head_io.c
> @@ -384,6 +384,8 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 block, int nr,
>   					goto read_failure;
>   			}
>   		}
> +		if (!bh)
> +			continue;

If you like the style of the above two lines, put them after the
line "bh = bhs[i];", or the code below is more concise:
```
                   * completed. */
+ 		if (bh)
   			ocfs2_set_buffer_uptodate(ci, bh);
```

Thanks,
Heming
>   
>   		/* Always set the buffer in the cache, even if it was
>   		 * a forced read, or read-ahead which hasn't yet