From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Subject: Re: [PATCH bpf-next] bpf: fix stacksafe exploration when comparing
 states
Date: Sat, 23 Dec 2017 11:08:14 -0800
Message-ID: <20171223190812.bh4gvbijrhrsqf4q@ast-mbp>
References: <20171223100955.7208-1-g.borello@gmail.com>
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Cc: netdev@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net
To: Gianluca Borello <g.borello@gmail.com>
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On Sat, Dec 23, 2017 at 10:09:55AM +0000, Gianluca Borello wrote:
... 
> Fixes: cc2b14d51053 ("bpf: teach verifier to recognize zero initialized stack")
> Signed-off-by: Gianluca Borello <g.borello@gmail.com>
> Acked-by: Alexei Starovoitov <ast@kernel.org>
> ---
>  kernel/bpf/verifier.c                       |  2 +-
>  tools/testing/selftests/bpf/test_verifier.c | 51 +++++++++++++++++++++++++++++
>  2 files changed, 52 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 8b442ae125d0..93e1c77dae1d 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -4107,7 +4107,7 @@ static bool stacksafe(struct bpf_func_state *old,
>  
>  		if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ))
>  			/* explored state didn't use this */
> -			return true;
> +			continue;

argh. Not sure what I was thinking.
Applied, Thanks a lot Gianluca!