linux-kernel - Re: [PATCH 4.19 026/239] f2fs: fix to do sanity check in is

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Date:   Tue, 25 Jan 2022 10:22:04 +0800
From:   Chao Yu <chao@...nel.org>
To:     Pavel Machek <pavel@...x.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jaegeuk Kim <jaegeuk@...nel.org>
Subject: Re: [PATCH 4.19 026/239] f2fs: fix to do sanity check in is_alive()

On 2022/1/25 4:36, Pavel Machek wrote:
> Hi!
> 
>> From: Chao Yu <chao@...nel.org>
>>
>> commit 77900c45ee5cd5da63bd4d818a41dbdf367e81cd upstream.
>>
>> In fuzzed image, SSA table may indicate that a data block belongs to
>> invalid node, which node ID is out-of-range (0, 1, 2 or max_nid), in
>> order to avoid migrating inconsistent data in such corrupted image,
>> let's do sanity check anyway before data block migration.
> 
> This may be good idea, but AFAICT this leads to leak of page reference.

Hi Pavel,

Oops, you're right, my bad.

> 
>> +++ b/fs/f2fs/gc.c
>> @@ -589,6 +589,9 @@ static bool is_alive(struct f2fs_sb_info
>>   		set_sbi_flag(sbi, SBI_NEED_FSCK);
>>   	}
>>   
>> +	if (f2fs_check_nid_range(sbi, dni->ino))
>> +		return false;
>> +
>>   	*nofs = ofs_of_node(node_page);
>>   	source_blkaddr = datablock_addr(NULL, node_page, ofs_in_node);
>>   	f2fs_put_page(node_page, 1);
> 
> AFAICT f2fs_put_page() needs to be done in the error path, too.
> 
> (Problem seems to exist in mainline, too).
> 
> Something like this?

Could you please send a formal patch to f2fs mailing list for better review?

Anyway, thanks a lot for the report and the patch!

Thanks,

> 
> Signed-off-by: Pavel Machek <pavel@...x.de>
> 
> Best regards,
> 								Pavel
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index ee308a8de432..e020804f7b07 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1038,8 +1038,10 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>   		set_sbi_flag(sbi, SBI_NEED_FSCK);
>   	}
>   
> -	if (f2fs_check_nid_range(sbi, dni->ino))
> +	if (f2fs_check_nid_range(sbi, dni->ino)) {
> +		f2fs_put_page(node_page, 1);
>   		return false;
> +	}
>   
>   	*nofs = ofs_of_node(node_page);
>   	source_blkaddr = data_blkaddr(NULL, node_page, ofs_in_node);
> 
>