netdev - Re: [PATCH net][v2] bpf: fix states equal logic for varlen access

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Message-ID: <583DD271.2020900@iogearbox.net>
Date:   Tue, 29 Nov 2016 20:09:37 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Josef Bacik <jbacik@...com>, davem@...emloft.net,
        netdev@...r.kernel.org, ast@...nel.org, jannh@...gle.com,
        kernel-team@...com
Subject: Re: [PATCH net][v2] bpf: fix states equal logic for varlen access

On 11/29/2016 06:27 PM, Josef Bacik wrote:
> If we have a branch that looks something like this
>
> int foo = map->value;
> if (condition) {
>    foo += blah;
> } else {
>    foo = bar;
> }
> map->array[foo] = baz;
>
> We will incorrectly assume that the !condition branch is equal to the condition
> branch as the register for foo will be UNKNOWN_VALUE in both cases.  We need to
> adjust this logic to only do this if we didn't do a varlen access after we
> processed the !condition branch, otherwise we have different ranges and need to
> check the other branch as well.
>
> Fixes: 484611357c19 ("bpf: allow access into map value arrays")
> Reported-by: Jann Horn <jannh@...gle.com>
> Signed-off-by: Josef Bacik <jbacik@...com>

Acked-by: Daniel Borkmann <daniel@...earbox.net>