linux-kernel - Re: [PATCH v2 1/2] f2fs: fix to avoid potential memory corruption in __update_iostat

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Message-ID: <da57fbad-8242-eb1e-ab2b-322d61d0762d@kernel.org>
Date:   Mon, 16 Jan 2023 21:25:27 +0800
From:   Chao Yu <chao@...nel.org>
To:     Yangtao Li <frank.li@...o.com>, jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Dan Carpenter <error27@...il.com>
Subject: Re: [PATCH v2 1/2] f2fs: fix to avoid potential memory corruption in
 __update_iostat_latency()

On 2023/1/16 21:02, Yangtao Li wrote:
> Add iotype sanity check to avoid potential memory corruption.
> This is to fix the compile error below:
> 
> fs/f2fs/iostat.c:231 __update_iostat_latency() error: buffer overflow
> 'io_lat->peak_lat[type]' 3 <= 3
> 
> vim +228 fs/f2fs/iostat.c
> 
>    211  static inline void __update_iostat_latency(struct bio_iostat_ctx
> 	*iostat_ctx,
>    212					enum iostat_lat_type type)
>    213  {
>    214		unsigned long ts_diff;
>    215		unsigned int page_type = iostat_ctx->type;
>    216		struct f2fs_sb_info *sbi = iostat_ctx->sbi;
>    217		struct iostat_lat_info *io_lat = sbi->iostat_io_lat;
>    218		unsigned long flags;
>    219
>    220		if (!sbi->iostat_enable)
>    221			return;
>    222
>    223		ts_diff = jiffies - iostat_ctx->submit_ts;
>    224		if (page_type >= META_FLUSH)
>                                   ^^^^^^^^^^
> 
>    225			page_type = META;
>    226
>    227		spin_lock_irqsave(&sbi->iostat_lat_lock, flags);
>   @228		io_lat->sum_lat[type][page_type] += ts_diff;
>                                        ^^^^^^^^^
> Mixup between META_FLUSH and NR_PAGE_TYPE leads to memory corruption.
> 
> Fixes: a4b6817625e7 ("f2fs: introduce periodic iostat io latency traces")
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <error27@...il.com>
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
>   fs/f2fs/iostat.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/iostat.c b/fs/f2fs/iostat.c
> index ed8176939aa5..e9a3df7ce4d9 100644
> --- a/fs/f2fs/iostat.c
> +++ b/fs/f2fs/iostat.c
> @@ -223,7 +223,7 @@ static inline void __update_iostat_latency(struct bio_iostat_ctx *iostat_ctx,
>   		return;
>   
>   	ts_diff = jiffies - iostat_ctx->submit_ts;
> -	if (iotype >= META_FLUSH)
> +	if (iotype == META_FLUSH)

Maybe it's betterr to merge these two check condition as below?

if (iotype >= NR_PAGE_TYPE) {
	f2fs_bug_on(sbi, iotype != META_FLUSH);
	iotype = META;
}

For CHECK_FS is off case, I guess it's fine to not return and just print
warning message for notice.

Thanks,

>   		iotype = META;
>   
>   	if (rw == 0) {
> @@ -235,6 +235,11 @@ static inline void __update_iostat_latency(struct bio_iostat_ctx *iostat_ctx,
>   			idx = WRITE_ASYNC_IO;
>   	}
>   
> +	if (iotype >= NR_PAGE_TYPE) {
> +		f2fs_bug_on(sbi, 1);
> +		return;
> +	}
> +
>   	spin_lock_irqsave(&sbi->iostat_lat_lock, flags);
>   	io_lat->sum_lat[idx][iotype] += ts_diff;
>   	io_lat->bio_cnt[idx][iotype]++;