netdev - Re: Help with the BPF verifier

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Message-Id: <20181101.121039.2134340499361533233.davem@davemloft.net>
Date:   Thu, 01 Nov 2018 12:10:39 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     acme@...nel.org
Cc:     yhs@...com, daniel@...earbox.net, jolsa@...hat.com, kafai@...com,
        alexei.starovoitov@...il.com, netdev@...r.kernel.org
Subject: Re: Help with the BPF verifier

From: Arnaldo Carvalho de Melo <acme@...nel.org>
Date: Thu, 1 Nov 2018 15:52:17 -0300

>     50		unsigned int filename_arg = 6;
 ...
> --- /wb/augmented_raw_syscalls.c.old	2018-11-01 15:43:55.000394234 -0300
> +++ /wb/augmented_raw_syscalls.c	2018-11-01 15:44:15.102367838 -0300
> @@ -67,7 +67,7 @@
>  		augmented_args.filename.reserved = 0;
>  		augmented_args.filename.size = probe_read_str(&augmented_args.filename.value,
>  							      sizeof(augmented_args.filename.value),
> -							      (const void *)args->args[0]);
> +							      (const void *)args->args[filename_arg]);

args[] is sized to '6', therefore the last valid index is '5', yet you're using '6' here which
is one entry past the end of the declared array.