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

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Date:   Wed, 30 Nov 2016 14:51:25 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     jbacik@...com
Cc:     netdev@...r.kernel.org, ast@...nel.org, jannh@...gle.com,
        daniel@...earbox.net, kernel-team@...com
Subject: Re: [PATCH net][v2] bpf: fix states equal logic for varlen access

From: Josef Bacik <jbacik@...com>
Date: Tue, 29 Nov 2016 12:27:09 -0500

> 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>
> ---
> v1->v2:
> - renamed and moved varlen_map_access variable.
> - dropped the extra () in the second if statement.
> - added the Fixes and Reported-by tag.

Applied, thanks.