linux-kernel - Re: [PATCH 5/6] treewide: use kv[mz]alloc* rather than opencoded variants

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Message-ID: <a4b4e2f4-f730-4f1d-7f41-36ba0d34f1a6@suse.cz>
Date:   Wed, 25 Jan 2017 12:15:59 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ben Skeggs <bskeggs@...hat.com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Santosh Raspatur <santosh@...lsio.com>,
        Hariprasad S <hariprasad@...lsio.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Yishai Hadas <yishaih@...lanox.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Oleg Drokin <oleg.drokin@...el.com>,
        Andreas Dilger <andreas.dilger@...el.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        David Sterba <dsterba@...e.com>,
        "Yan, Zheng" <zyan@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH 5/6] treewide: use kv[mz]alloc* rather than opencoded
 variants

On 01/24/2017 04:00 PM, Michal Hocko wrote:
>> > Well, I am not opposed to kvmalloc_array but I would argue that this
>> > conversion cannot introduce new overflow issues. The code would have
>> > to be broken already because even though kmalloc_array checks for the
>> > overflow but vmalloc fallback doesn't...
>>
>> Yeah I agree, but if some of the places were really wrong, after the
>> conversion we won't see them anymore.
>>
>> > If there is a general interest for this API I can add it.
>>
>> I think it would be better, yes.
>
> OK, fair enough. I will fold the following into the original patch. I
> was little bit reluctant to create kvcalloc so I've made the original
> callers more talkative and added | __GFP_ZERO.

Fair enough,

> To be honest I do not
> really like how kcalloc...

how kcalloc what?

[...]
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index cdc55d5ee4ad..eca16612b1ae 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -712,10 +712,7 @@ EXPORT_SYMBOL(xt_check_entry_offsets);
>   */
>  unsigned int *xt_alloc_entry_offsets(unsigned int size)
>  {
> -	if (size < (SIZE_MAX / sizeof(unsigned int)))
> -		return kvzalloc(size * sizeof(unsigned int), GFP_KERNEL);
> -
> -	return NULL;
> +	return kvmalloc_array(size * sizeof(unsigned int), GFP_KERNEL | __GFP_ZERO);

This one wouldn't compile.