Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211209115944.4062384-1-mpe@ellerman.id.au
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tools/testing/selftests/powerpc/signal/.gitignore
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tools/testing/selftests/powerpc/signal/.gitignore
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tools/testing/selftests/powerpc/signal/Makefile
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tools/testing/selftests/powerpc/signal/Makefile
+132
tools/testing/selftests/powerpc/signal/sigreturn_kernel.c
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tools/testing/selftests/powerpc/signal/sigreturn_kernel.c
···
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Test that we can't sigreturn to kernel addresses, or to kernel mode.
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include "utils.h"
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#define MSR_PR (1ul << 14)
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static volatile unsigned long long sigreturn_addr;
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static volatile unsigned long long sigreturn_msr_mask;
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static void sigusr1_handler(int signo, siginfo_t *si, void *uc_ptr)
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{
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ucontext_t *uc = (ucontext_t *)uc_ptr;
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if (sigreturn_addr)
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UCONTEXT_NIA(uc) = sigreturn_addr;
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if (sigreturn_msr_mask)
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UCONTEXT_MSR(uc) &= sigreturn_msr_mask;
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}
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static pid_t fork_child(void)
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{
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pid_t pid;
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pid = fork();
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if (pid == 0) {
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raise(SIGUSR1);
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exit(0);
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}
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return pid;
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}
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static int expect_segv(pid_t pid)
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{
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int child_ret;
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waitpid(pid, &child_ret, 0);
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FAIL_IF(WIFEXITED(child_ret));
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FAIL_IF(!WIFSIGNALED(child_ret));
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FAIL_IF(WTERMSIG(child_ret) != 11);
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return 0;
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}
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int test_sigreturn_kernel(void)
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{
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struct sigaction act;
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int child_ret, i;
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pid_t pid;
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act.sa_sigaction = sigusr1_handler;
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act.sa_flags = SA_SIGINFO;
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sigemptyset(&act.sa_mask);
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FAIL_IF(sigaction(SIGUSR1, &act, NULL));
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for (i = 0; i < 2; i++) {
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// Return to kernel
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sigreturn_addr = 0xcull << 60;
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pid = fork_child();
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expect_segv(pid);
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// Return to kernel virtual
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sigreturn_addr = 0xc008ull << 48;
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pid = fork_child();
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expect_segv(pid);
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// Return out of range
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sigreturn_addr = 0xc010ull << 48;
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pid = fork_child();
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expect_segv(pid);
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// Return to no-man's land, just below PAGE_OFFSET
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sigreturn_addr = (0xcull << 60) - (64 * 1024);
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pid = fork_child();
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expect_segv(pid);
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// Return to no-man's land, above TASK_SIZE_4PB
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sigreturn_addr = 0x1ull << 52;
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pid = fork_child();
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expect_segv(pid);
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// Return to 0xd space
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sigreturn_addr = 0xdull << 60;
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pid = fork_child();
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expect_segv(pid);
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// Return to 0xe space
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sigreturn_addr = 0xeull << 60;
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pid = fork_child();
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expect_segv(pid);
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// Return to 0xf space
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sigreturn_addr = 0xfull << 60;
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pid = fork_child();
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expect_segv(pid);
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// Attempt to set PR=0 for 2nd loop (should be blocked by kernel)
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sigreturn_msr_mask = ~MSR_PR;
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}
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printf("All children killed as expected\n");
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// Don't change address, just MSR, should return to user as normal
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sigreturn_addr = 0;
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sigreturn_msr_mask = ~MSR_PR;
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pid = fork_child();
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waitpid(pid, &child_ret, 0);
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FAIL_IF(!WIFEXITED(child_ret));
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FAIL_IF(WIFSIGNALED(child_ret));
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FAIL_IF(WEXITSTATUS(child_ret) != 0);
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return 0;
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}
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int main(void)
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{
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return test_harness(test_sigreturn_kernel, "sigreturn_kernel");
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}