linux-kernel - Re: [PATCH bpf-next] bpf: btf: Fix arg verification in btf_ctx

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Date:   Mon, 30 Mar 2020 13:32:16 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     KP Singh <kpsingh@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next] bpf: btf: Fix arg verification in btf_ctx_access()

On Mon, Mar 30, 2020 at 7:43 AM KP Singh <kpsingh@...omium.org> wrote:
>
> From: KP Singh <kpsingh@...gle.com>
>
> The bounds checking for the arguments accessed in the BPF program breaks
> when the expected_attach_type is not BPF_TRACE_FEXIT, BPF_LSM_MAC or
> BPF_MODIFY_RETURN resulting in no check being done for the default case
> (the programs which do not receive the return value of the attached
> function in its arguments) when the index of the argument being accessed
> is equal to the number of arguments (nr_args).
>
> This was a result of a misplaced "else if" block  introduced by the
> Commit 6ba43b761c41 ("bpf: Attachment verification for
> BPF_MODIFY_RETURN")
>
> Signed-off-by: KP Singh <kpsingh@...gle.com>
> Fixes: 6ba43b761c41 ("bpf: Attachment verification for BPF_MODIFY_RETURN")
> Reported-by: Jann Horn <jannh@...gle.com>

Applied. Thanks