linux-hardening - Re: [PATCH 03/12] net: ipa: Proactively round up to kmalloc bucket size

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Message-ID: <202209220857.A6EBCF031E@keescook>
Date:   Thu, 22 Sep 2022 08:57:46 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Alex Elder <elder@...e.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, Alex Elder <elder@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Daniel Micay <danielmicay@...il.com>,
        Yonghong Song <yhs@...com>, Marco Elver <elver@...gle.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Jacob Shin <jacob.shin@....com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-btrfs@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, linux-fsdevel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, dev@...nvswitch.org,
        x86@...nel.org, linux-wireless@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 03/12] net: ipa: Proactively round up to kmalloc bucket
 size

On Thu, Sep 22, 2022 at 08:45:19AM -0500, Alex Elder wrote:
> On 9/21/22 10:10 PM, Kees Cook wrote:
> > Instead of discovering the kmalloc bucket size _after_ allocation, round
> > up proactively so the allocation is explicitly made for the full size,
> > allowing the compiler to correctly reason about the resulting size of
> > the buffer through the existing __alloc_size() hint.
> > 
> > Cc: Alex Elder <elder@...nel.org>
> > Cc: "David S. Miller" <davem@...emloft.net>
> > Cc: Eric Dumazet <edumazet@...gle.com>
> > Cc: Jakub Kicinski <kuba@...nel.org>
> > Cc: Paolo Abeni <pabeni@...hat.com>
> > Cc: netdev@...r.kernel.org
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> >   drivers/net/ipa/gsi_trans.c | 7 +++++--
> >   1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
> > index 18e7e8c405be..cec968854dcf 100644
> > --- a/drivers/net/ipa/gsi_trans.c
> > +++ b/drivers/net/ipa/gsi_trans.c
> > @@ -89,6 +89,7 @@ int gsi_trans_pool_init(struct gsi_trans_pool *pool, size_t size, u32 count,
> >   			u32 max_alloc)
> >   {
> >   	void *virt;
> > +	size_t allocate;
> 
> I don't care about this but the reverse Christmas tree
> convention would put the "allocate" variable definition
> above "virt".

Oops, yes; thank you!

-Kees

-- 
Kees Cook