Re: [PATCH v2 2/2] selftests: add tests for prctl(SET_HIDE_SELF_EXE)

Giuseppe Scrivano
2023-01-19T18:05:11Z

Brian Masney <bmasney@redhat.com> writes:

> 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?

you are right, thanks for spotting it! I should test
PR_SET_HIDE_SELF_EXE not the getter.