linux-kernel - Re: [PATCH 5/9] treewide: use kv[mz]alloc* rather than opencoded variants

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Date:   Mon, 30 Jan 2017 11:24:02 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        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>,
        Michal Hocko <mhocko@...e.com>,
        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>,
        Yishai Hadas <yishaih@...lanox.com>,
        Oleg Drokin <oleg.drokin@...el.com>,
        "Yan, Zheng" <zyan@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH 5/9] treewide: use kv[mz]alloc* rather than opencoded variants

On Mon, Jan 30, 2017 at 1:49 AM, Michal Hocko <mhocko@...nel.org> wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> There are many code paths opencoding kvmalloc. Let's use the helper
> instead. The main difference to kvmalloc is that those users are usually
> not considering all the aspects of the memory allocator. E.g. allocation
> requests <= 32kB (with 4kB pages) are basically never failing and invoke
> OOM killer to satisfy the allocation. This sounds too disruptive for
> something that has a reasonable fallback - the vmalloc. On the other
> hand those requests might fallback to vmalloc even when the memory
> allocator would succeed after several more reclaim/compaction attempts
> previously. There is no guarantee something like that happens though.
>
> This patch converts many of those places to kv[mz]alloc* helpers because
> they are more conservative.
>
> Changes since v1
> - add kvmalloc_array - this might silently fix some overflow issues
>   because most users simply didn't check the overflow for the vmalloc
>   fallback.

Awesome, thanks for adding that API. :)

Acked-by: Kees Cook <keescook@...omium.org>

-Kees

-- 
Kees Cook
Nexus Security