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Date:   Thu, 22 Sep 2022 08:57:46 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Alex Elder <elder@ieee.org>
Cc:     Vlastimil Babka <vbabka@suse.cz>, Alex Elder <elder@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
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        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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Subject: Re: [PATCH 03/12] net: ipa: Proactively round up to kmalloc bucket
 size
Message-ID: <202209220857.A6EBCF031E@keescook>
References: <20220922031013.2150682-1-keescook@chromium.org>
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 <4d75a9fd-1b94-7208-9de8-5a0102223e68@ieee.org>
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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@kernel.org>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: Eric Dumazet <edumazet@google.com>
> > Cc: Jakub Kicinski <kuba@kernel.org>
> > Cc: Paolo Abeni <pabeni@redhat.com>
> > Cc: netdev@vger.kernel.org
> > Signed-off-by: Kees Cook <keescook@chromium.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