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

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Message-ID: <Y8ihpXw81e2FH2um@google.com>
Date:   Wed, 18 Jan 2023 17:49:25 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Yangtao Li <frank.li@...o.com>
Cc:     chao@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH v2 1/2] f2fs: fix to avoid potential memory
 corruption in __update_iostat_latency()

On 01/16, Yangtao Li wrote:
> Hi Chao,
> 
> > 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 normal , only META_FLUSH will be greater than NR_PAGE_TYPE,
> there is no problem with this logic.
> 
> >
> > For CHECK_FS is off case, I guess it's fine to not return and just print
> > warning message for notice.
> 
> But if there is an exception, we don't know the type we originally wanted to count.
> If they are all changed to meta, it is possible to get a wrong statistic. I think
> there is no need to make statistics on this kind of error scene. Just like in the
> next patch, if iostat_lat_type is wrong, we should return directly instead of changing
> the value beyond the range to WRITE_ASYNC_IO.
> 
> So it's no need tp merge these two check condition?

I also prefer to do like Chao's comment. We don't need to expect such exception
at all.

And, it seems we just need to do like:

	enum page_type iotype;

	if (iotype == META_FLUSH) {
		iotype = META;
	} else if (iotype >= NR_PAGE_TYPE) {
		f2fs_warn();
		return;
	}

> 
> Thx,
> Yangtao