linux-kernel - Re: [RFC 2/2] kvm: eventfd: detect integer overflow using check_*

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Date:	Wed, 26 Nov 2014 21:50:15 +0400
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	mingo <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 2/2] kvm: eventfd: detect integer overflow using check_*_overflow

2014-11-26 17:00 GMT+03:00 Sasha Levin <sasha.levin@...cle.com>:
> Detect integer overflows using safe operations rather than relying on
> undefined behaviour.
>

Unsigned overflow is defined.
args->addr and args->len  both unsigned, so there is no UB here.

> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  virt/kvm/eventfd.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index 148b239..2eb044f 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -790,7 +790,7 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
>         }
>
>         /* check for range overflow */
> -       if (args->addr + args->len < args->addr)
> +       if (check_add_overflow(args->len, args->addr))
>                 return -EINVAL;
>
>         /* check for extra flags that we don't understand */
> --
> 1.7.10.4
>
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