linux-kernel - Re: [PATCH bpf-next v3 2/2] bpf: Add tests for bpf_lsm_set_bprm

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Date:   Mon, 16 Nov 2020 22:18:16 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     KP Singh <kpsingh@...omium.org>
CC:     <linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Florent Revest <revest@...omium.org>,
        Brendan Jackman <jackmanb@...omium.org>,
        Pauline Middelink <middelin@...gle.com>
Subject: Re: [PATCH bpf-next v3 2/2] bpf: Add tests for bpf_lsm_set_bprm_opts

On Tue, Nov 17, 2020 at 02:13:07AM +0000, KP Singh wrote:
> From: KP Singh <kpsingh@...gle.com>
> 
> The test forks a child process, updates the local storage to set/unset
> the securexec bit.
> 
> The BPF program in the test attaches to bprm_creds_for_exec which checks
> the local storage of the current task to set the secureexec bit on the
> binary parameters (bprm).
> 
> The child then execs a bash command with the environment variable
> TMPDIR set in the envp.  The bash command returns a different exit code
> based on its observed value of the TMPDIR variable.
> 
> Since TMPDIR is one of the variables that is ignored by the dynamic
> loader when the secureexec bit is set, one should expect the
> child execution to not see this value when the secureexec bit is set.
> 
> Signed-off-by: KP Singh <kpsingh@...gle.com>
Acked-by: Martin KaFai Lau <kafai@...com>