Commit a8968521 authored by Michael Ellerman's avatar Michael Ellerman
Browse files

selftests/powerpc: Add a test of sigreturning to the kernel 



We have a general signal fuzzer, sigfuz, which can modify the MSR & NIP
before sigreturn. But the chance of it hitting a kernel address and also
clearing MSR_PR is fairly slim.

So add a specific test of sigreturn to a kernel address, both with and
without attempting to clear MSR_PR (which the kernel must block).

Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211209115944.4062384-1-mpe@ellerman.id.au
parent 9cbbe6ba

tools/testing/selftests/powerpc/signal/.gitignore

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@@ -4,3 +4,4 @@ signal_tm 
sigfuz

sigreturn_vdso

sig_sc_double_restart

sigreturn_kernel

tools/testing/selftests/powerpc/signal/Makefile

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# SPDX-License-Identifier: GPL-2.0

TEST_GEN_PROGS := signal signal_tm sigfuz sigreturn_vdso sig_sc_double_restart

TEST_GEN_PROGS += sigreturn_kernel



CFLAGS += -maltivec

$(OUTPUT)/signal_tm: CFLAGS += -mhtm

tools/testing/selftests/powerpc/signal/sigreturn_kernel.c

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// SPDX-License-Identifier: GPL-2.0

/*

 * Test that we can't sigreturn to kernel addresses, or to kernel mode.

 */



#define _GNU_SOURCE



#include <stdio.h>

#include <signal.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>



#include "utils.h"



#define MSR_PR (1ul << 14)



static volatile unsigned long long sigreturn_addr;

static volatile unsigned long long sigreturn_msr_mask;



static void sigusr1_handler(int signo, siginfo_t *si, void *uc_ptr)

{

	ucontext_t *uc = (ucontext_t *)uc_ptr;



	if (sigreturn_addr)

		UCONTEXT_NIA(uc) = sigreturn_addr;



	if (sigreturn_msr_mask)

		UCONTEXT_MSR(uc) &= sigreturn_msr_mask;

}



static pid_t fork_child(void)

{

	pid_t pid;



	pid = fork();

	if (pid == 0) {

		raise(SIGUSR1);

		exit(0);

	}



	return pid;

}



static int expect_segv(pid_t pid)

{

	int child_ret;



	waitpid(pid, &child_ret, 0);

	FAIL_IF(WIFEXITED(child_ret));

	FAIL_IF(!WIFSIGNALED(child_ret));

	FAIL_IF(WTERMSIG(child_ret) != 11);



	return 0;

}



int test_sigreturn_kernel(void)

{

	struct sigaction act;

	int child_ret, i;

	pid_t pid;



	act.sa_sigaction = sigusr1_handler;

	act.sa_flags = SA_SIGINFO;

	sigemptyset(&act.sa_mask);



	FAIL_IF(sigaction(SIGUSR1, &act, NULL));



	for (i = 0; i < 2; i++) {

		// Return to kernel

		sigreturn_addr = 0xcull << 60;

		pid = fork_child();

		expect_segv(pid);



		// Return to kernel virtual

		sigreturn_addr = 0xc008ull << 48;

		pid = fork_child();

		expect_segv(pid);



		// Return out of range

		sigreturn_addr = 0xc010ull << 48;

		pid = fork_child();

		expect_segv(pid);



		// Return to no-man's land, just below PAGE_OFFSET

		sigreturn_addr = (0xcull << 60) - (64 * 1024);

		pid = fork_child();

		expect_segv(pid);



		// Return to no-man's land, above TASK_SIZE_4PB

		sigreturn_addr = 0x1ull << 52;

		pid = fork_child();

		expect_segv(pid);



		// Return to 0xd space

		sigreturn_addr = 0xdull << 60;

		pid = fork_child();

		expect_segv(pid);



		// Return to 0xe space

		sigreturn_addr = 0xeull << 60;

		pid = fork_child();

		expect_segv(pid);



		// Return to 0xf space

		sigreturn_addr = 0xfull << 60;

		pid = fork_child();

		expect_segv(pid);



		// Attempt to set PR=0 for 2nd loop (should be blocked by kernel)

		sigreturn_msr_mask = ~MSR_PR;

	}



	printf("All children killed as expected\n");



	// Don't change address, just MSR, should return to user as normal

	sigreturn_addr = 0;

	sigreturn_msr_mask = ~MSR_PR;

	pid = fork_child();

	waitpid(pid, &child_ret, 0);

	FAIL_IF(!WIFEXITED(child_ret));

	FAIL_IF(WIFSIGNALED(child_ret));

	FAIL_IF(WEXITSTATUS(child_ret) != 0);



	return 0;

}



int main(void)

{

	return test_harness(test_sigreturn_kernel, "sigreturn_kernel");

}