linux-kernel - Re: [PATCH] zram: explicitly limit prio

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Date:   Tue, 15 Nov 2022 09:47:07 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Minchan Kim <minchan@...nel.org>,
        Nitin Gupta <ngupta@...are.org>,
        Suleiman Souhlal <suleiman@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        coverity-bot <keescook+coverity-bot@...omium.org>
Subject: Re: [PATCH] zram: explicitly limit prio_max for static analyzers

On (22/11/14 16:41), Andrew Morton wrote:
> >  drivers/block/zram/zram_drv.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index 9d33801e8ba8..e67a124f2e88 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -1706,6 +1706,7 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
> >  	 * Iterate the secondary comp algorithms list (in order of priority)
> >  	 * and try to recompress the page.
> >  	 */
> > +	prio_max = min(prio_max, ZRAM_MAX_COMPS);
> >  	for (; prio < prio_max; prio++) {
> >  		if (!zram->comps[prio])
> >  			continue;
> 
> I'll queue this as a fix to "zram: introduce recompress sysfs knob".
> 
> What's it do?  A little changelog would be nice, or at least a link to
> the coverity report?

It doesn't do much, coverity (static analyzer?) got confused by
the code, so this simply is supposed to help coverity figure out
that we never do an out of bounds access in comps[] array:
https://lore.kernel.org/lkml/202211100847.388C61B3@keescook/