@@ -1,5 +1,6 @@
# 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
new file mode 100644
@@ -0,0 +1,132 @@
+// 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");
+}
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> --- .../testing/selftests/powerpc/signal/Makefile | 1 + .../powerpc/signal/sigreturn_kernel.c | 132 ++++++++++++++++++ 2 files changed, 133 insertions(+) create mode 100644 tools/testing/selftests/powerpc/signal/sigreturn_kernel.c