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Date:   Thu, 19 Jan 2023 12:44:07 -0500
From:   Brian Masney <bmasney@redhat.com>
To:     Giuseppe Scrivano <gscrivan@redhat.com>
Cc:     linux-kernel@vger.kernel.org, keescook@chromium.org,
        bristot@redhat.com, ebiederm@xmission.com, brauner@kernel.org,
        cyphar@cyphar.com, viro@zeniv.linux.org.uk, alexl@redhat.com,
        peterz@infradead.org
Subject: Re: [PATCH v2 2/2] selftests: add tests for prctl(SET_HIDE_SELF_EXE)
Message-ID: <Y8mBZ5I8Yx4TARjb@x1>
References: <20230119170718.3129938-1-gscrivan@redhat.com>
 <20230119170718.3129938-2-gscrivan@redhat.com>
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On Thu, Jan 19, 2023 at 06:07:18PM +0100, Giuseppe Scrivano wrote:
> Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
> ---
>  tools/testing/selftests/prctl/Makefile        |   2 +-
>  tools/testing/selftests/prctl/hide-self-exe.c | 101 ++++++++++++++++++
>  2 files changed, 102 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/prctl/hide-self-exe.c
> 
> diff --git a/tools/testing/selftests/prctl/Makefile b/tools/testing/selftests/prctl/Makefile
> index c7923b205222..024e107b26ec 100644
> --- a/tools/testing/selftests/prctl/Makefile
> +++ b/tools/testing/selftests/prctl/Makefile
> @@ -5,7 +5,7 @@ ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
>  
>  ifeq ($(ARCH),x86)
>  TEST_PROGS := disable-tsc-ctxt-sw-stress-test disable-tsc-on-off-stress-test \
> -		disable-tsc-test
> +		disable-tsc-test hide-self-exe
>  all: $(TEST_PROGS)
>  
>  include ../lib.mk
> diff --git a/tools/testing/selftests/prctl/hide-self-exe.c b/tools/testing/selftests/prctl/hide-self-exe.c
> new file mode 100644
> index 000000000000..f86cef8e061c
> --- /dev/null
> +++ b/tools/testing/selftests/prctl/hide-self-exe.c
> @@ -0,0 +1,101 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Tests for prctl(PR_GET_HIDE_SELF_EXE, ...) / prctl(PR_SET_HIDE_SELF_EXE, ...)
> + *
> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <signal.h>
> +#include <inttypes.h>
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <sys/wait.h>
> +
> +#include <sys/prctl.h>
> +#include <linux/prctl.h>
> +
> +#ifndef PR_SET_HIDE_SELF_EXE
> +# define PR_SET_HIDE_SELF_EXE		65
> +# define PR_GET_HIDE_SELF_EXE		66
> +#endif
> +
> +int main(void)
> +{
> +	int status;
> +	pid_t pid;
> +	int ret;
> +
> +	ret = open("/proc/self/exe", O_RDONLY);
> +	if (ret < 0) {
> +		perror("open /proc/self/exe");
> +		exit(EXIT_FAILURE);
> +	}
> +	close(ret);
> +
> +	ret = prctl(PR_GET_HIDE_SELF_EXE, 0, 0, 0, 0);
> +	if (ret != 0) {
> +		perror("prctl(PR_GET_HIDE_SELF_EXE)");
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	ret = prctl(PR_SET_HIDE_SELF_EXE, 1, 0, 0, 0);
> +	if (ret != 0) {
> +		perror("prctl(PR_SET_HIDE_SELF_EXE)");
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	/* check it doesn't fail a second time.  */
> +	ret = prctl(PR_SET_HIDE_SELF_EXE, 1, 0, 0, 0);
> +	if (ret != 0) {
> +		perror("prctl(PR_SET_HIDE_SELF_EXE)");
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	ret = prctl(PR_GET_HIDE_SELF_EXE, 0, 0, 0, 0);
> +	if (ret != 1) {
> +		perror("prctl(PR_GET_HIDE_SELF_EXE)");
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	ret = open("/proc/self/exe", O_RDONLY);
> +	if (ret >= 0 || errno != ENOENT) {
> +		perror("open /proc/self/exe succeeded");
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	pid = fork();
> +	if (pid < 0) {
> +		perror("fork");
> +		exit(EXIT_FAILURE);
> +	}
> +	if (pid == 0) {
> +		/* Verify that it is still unreachable after fork().  */
> +		ret = open("/proc/self/exe", O_RDONLY);
> +		if (ret >= 0 || errno != ENOENT)
> +			exit(EXIT_FAILURE);
> +		close(ret);
> +
> +		/* And that it cannot be unset.  */
> +		ret = prctl(PR_GET_HIDE_SELF_EXE, 0, 0, 0, 0);

Should this be PR_SET_HIDE_SELF_EXE?

Brian