linux-kernel - Re: [PATCH] mm/damon/core: fix divide error in damon_nr_accesses_to_accesses

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Message-Id: <20230527023149.8441-1-sj@kernel.org>
Date:   Fri, 26 May 2023 19:31:49 -0700
From:   SeongJae Park <sj@...nel.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     SeongJae Park <sj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        damon@...ts.linux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        syzbot+841a46899768ec7bec67@...kaller.appspotmail.com
Subject: Re: [PATCH] mm/damon/core: fix divide error in damon_nr_accesses_to_accesses_bp()

Hi Kefeng,

Thank you so much for this awesome patch!

On Sat, 27 May 2023 10:33:30 +0800 Kefeng Wang <wangkefeng.wang@...wei.com> wrote:

> If 'aggr_interval' is smaller than 'sample_interval', max_nr_accesses becomes
> zero which leads to divide error in damon_nr_accesses_to_accesses_bp(), let's
> validate the values of them in damon_set_attrs() to fix it, which similar to
> others attrs check.
> 
> Reported-by: syzbot+841a46899768ec7bec67@...kaller.appspotmail.com

I think it would be good to add the link to the report, e.g.,
"Link: https://lore.kernel.org/damon/00000000000055fc4e05fc975bc2@google.com/"

> Fixes: 2f5bef5a590b ("mm/damon/core: update monitoring results for new monitoring attributes")

Could you please add 'Cc: <stable@...r.kernel.org> # 6.3.x-' ?

Also, checkpatch.pl raises below warnings.

```
WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#61: 
If 'aggr_interval' is smaller than 'sample_interval', max_nr_accesses becomes

WARNING: Reported-by: should be immediately followed by Closes: with a URL to the report
#66: 
Reported-by: syzbot+841a46899768ec7bec67@...kaller.appspotmail.com
Fixes: 2f5bef5a590b ("mm/damon/core: update monitoring results for new monitoring attributes")

total: 0 errors, 2 warnings, 8 lines checked
```

Could you please resolve those by wrapping the commit messages and adding
'Closes:' tag?  'Closes:' tag might be able to replace the 'Link:' tag I
supposed above.  I have no strong opinions there but having both may harm
nothing.

Other than those,

Reviewed-by: SeongJae Park <sj@...nel.org>


Thanks,
SJ

> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  mm/damon/core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index d9ef62047bf5..91cff7f2997e 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -551,6 +551,8 @@ int damon_set_attrs(struct damon_ctx *ctx, struct damon_attrs *attrs)
>  		return -EINVAL;
>  	if (attrs->min_nr_regions > attrs->max_nr_regions)
>  		return -EINVAL;
> +	if (attrs->sample_interval > attrs->aggr_interval)
> +		return -EINVAL;
>  
>  	damon_update_monitoring_results(ctx, attrs);
>  	ctx->attrs = *attrs;
> -- 
> 2.35.3
>