netdev - Re: [net PATCH] bpf: devmap fix arithmetic overflow in bitmap

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Message-ID: <20171019221245.a7grq3csbpixjgpn@ast-mbp>
Date:   Thu, 19 Oct 2017 15:12:46 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     John Fastabend <john.r.fastabend@...il.com>
Cc:     richard@....at, davem@...emloft.net, netdev@...r.kernel.org,
        borkmann@...earbox.net
Subject: Re: [net PATCH] bpf: devmap fix arithmetic overflow in bitmap_size
 calculation

On Thu, Oct 19, 2017 at 09:03:52AM -0700, John Fastabend wrote:
> An integer overflow is possible in dev_map_bitmap_size() when
> calculating the BITS_TO_LONG logic which becomes, after macro
> replacement,
> 
> 	(((n) + (d) - 1)/ (d))
> 
> where 'n' is a __u32 and 'd' is (8 * sizeof(long)). To avoid
> overflow cast to u64 before arithmetic.
> 
> Reported-by: Richard Weinberger <richard@....at>
> Acked-by: Daniel Borkmann <daniel@...earbox.net>
> Signed-off-by: John Fastabend <john.fastabend@...il.com>

Acked-by: Alexei Starovoitov <ast@...nel.org>