[PATCH 3/4] kselftests/arm64: add PAuth test for whether exec() changes keys
Boyan Karatotev
boyan.karatotev at arm.com
Fri Aug 28 09:16:05 EDT 2020
Kernel documentation states that it will change PAuth keys on exec() calls.
Verify that all keys are correctly switched to new ones.
Cc: Shuah Khan <shuah at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Signed-off-by: Boyan Karatotev <boyan.karatotev at arm.com>
---
tools/testing/selftests/arm64/pauth/Makefile | 4 +
.../selftests/arm64/pauth/exec_target.c | 35 +++++
tools/testing/selftests/arm64/pauth/helper.h | 10 ++
tools/testing/selftests/arm64/pauth/pac.c | 148 ++++++++++++++++++
4 files changed, 197 insertions(+)
create mode 100644 tools/testing/selftests/arm64/pauth/exec_target.c
diff --git a/tools/testing/selftests/arm64/pauth/Makefile b/tools/testing/selftests/arm64/pauth/Makefile
index a017d1c8dd58..2e237b21ccf6 100644
--- a/tools/testing/selftests/arm64/pauth/Makefile
+++ b/tools/testing/selftests/arm64/pauth/Makefile
@@ -5,6 +5,7 @@ CFLAGS += -mbranch-protection=pac-ret
TEST_GEN_PROGS := pac
TEST_GEN_FILES := pac_corruptor.o helper.o
+TEST_GEN_PROGS_EXTENDED := exec_target
include ../../lib.mk
@@ -20,6 +21,9 @@ $(OUTPUT)/helper.o: helper.c
# greater, gcc emits pac* instructions which are not in HINT NOP space,
# preventing the tests from occurring at all. Compile for ARMv8.2 so tests can
# run on earlier targets and print a meaningful error messages
+$(OUTPUT)/exec_target: exec_target.c $(OUTPUT)/helper.o
+ $(CC) $^ -o $@ $(CFLAGS) -march=armv8.2-a
+
$(OUTPUT)/pac: pac.c $(OUTPUT)/pac_corruptor.o $(OUTPUT)/helper.o
$(CC) $^ -o $@ $(CFLAGS) -march=armv8.2-a
diff --git a/tools/testing/selftests/arm64/pauth/exec_target.c b/tools/testing/selftests/arm64/pauth/exec_target.c
new file mode 100644
index 000000000000..07addef5a1d7
--- /dev/null
+++ b/tools/testing/selftests/arm64/pauth/exec_target.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2020 ARM Limited
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/auxv.h>
+
+#include "helper.h"
+
+
+int main(void)
+{
+ struct signatures signed_vals;
+ unsigned long hwcaps;
+ size_t val;
+
+ fread(&val, sizeof(size_t), 1, stdin);
+
+ /* don't try to execute illegal (unimplemented) instructions) caller
+ * should have checked this and keep worker simple
+ */
+ hwcaps = getauxval(AT_HWCAP);
+
+ if (hwcaps & HWCAP_PACA) {
+ signed_vals.keyia = keyia_sign(val);
+ signed_vals.keyib = keyib_sign(val);
+ signed_vals.keyda = keyda_sign(val);
+ signed_vals.keydb = keydb_sign(val);
+ }
+ signed_vals.keyg = (hwcaps & HWCAP_PACG) ? keyg_sign(val) : 0;
+
+ fwrite(&signed_vals, sizeof(struct signatures), 1, stdout);
+
+ return 0;
+}
diff --git a/tools/testing/selftests/arm64/pauth/helper.h b/tools/testing/selftests/arm64/pauth/helper.h
index b3cf709e249d..fceaa1e4824a 100644
--- a/tools/testing/selftests/arm64/pauth/helper.h
+++ b/tools/testing/selftests/arm64/pauth/helper.h
@@ -6,6 +6,16 @@
#include <stdlib.h>
+#define NKEYS 5
+
+
+struct signatures {
+ size_t keyia;
+ size_t keyib;
+ size_t keyda;
+ size_t keydb;
+ size_t keyg;
+};
void pac_corruptor(void);
diff --git a/tools/testing/selftests/arm64/pauth/pac.c b/tools/testing/selftests/arm64/pauth/pac.c
index cdbffa8bf61e..16dea47b11c7 100644
--- a/tools/testing/selftests/arm64/pauth/pac.c
+++ b/tools/testing/selftests/arm64/pauth/pac.c
@@ -2,6 +2,8 @@
// Copyright (C) 2020 ARM Limited
#include <sys/auxv.h>
+#include <sys/types.h>
+#include <sys/wait.h>
#include <signal.h>
#include "../../kselftest_harness.h"
@@ -33,6 +35,117 @@ do { \
} while (0)
+void sign_specific(struct signatures *sign, size_t val)
+{
+ sign->keyia = keyia_sign(val);
+ sign->keyib = keyib_sign(val);
+ sign->keyda = keyda_sign(val);
+ sign->keydb = keydb_sign(val);
+}
+
+void sign_all(struct signatures *sign, size_t val)
+{
+ sign->keyia = keyia_sign(val);
+ sign->keyib = keyib_sign(val);
+ sign->keyda = keyda_sign(val);
+ sign->keydb = keydb_sign(val);
+ sign->keyg = keyg_sign(val);
+}
+
+int are_same(struct signatures *old, struct signatures *new, int nkeys)
+{
+ int res = 0;
+
+ res |= old->keyia == new->keyia;
+ res |= old->keyib == new->keyib;
+ res |= old->keyda == new->keyda;
+ res |= old->keydb == new->keydb;
+ if (nkeys == NKEYS)
+ res |= old->keyg == new->keyg;
+
+ return res;
+}
+
+int exec_sign_all(struct signatures *signed_vals, size_t val)
+{
+ int new_stdin[2];
+ int new_stdout[2];
+ int status;
+ ssize_t ret;
+ pid_t pid;
+
+ ret = pipe(new_stdin);
+ if (ret == -1) {
+ perror("pipe returned error");
+ return -1;
+ }
+
+ ret = pipe(new_stdout);
+ if (ret == -1) {
+ perror("pipe returned error");
+ return -1;
+ }
+
+ pid = fork();
+ // child
+ if (pid == 0) {
+ dup2(new_stdin[0], STDIN_FILENO);
+ if (ret == -1) {
+ perror("dup2 returned error");
+ exit(1);
+ }
+
+ dup2(new_stdout[1], STDOUT_FILENO);
+ if (ret == -1) {
+ perror("dup2 returned error");
+ exit(1);
+ }
+
+ close(new_stdin[0]);
+ close(new_stdin[1]);
+ close(new_stdout[0]);
+ close(new_stdout[1]);
+
+ ret = execl("exec_target", "exec_target", (char *) NULL);
+ if (ret == -1) {
+ perror("exec returned error");
+ exit(1);
+ }
+ }
+
+ close(new_stdin[0]);
+ close(new_stdout[1]);
+
+ ret = write(new_stdin[1], &val, sizeof(size_t));
+ if (ret == -1) {
+ perror("write returned error");
+ return -1;
+ }
+
+ /*
+ * wait for the worker to finish, so that read() reads all data
+ * will also context switch with worker so that this function can be used
+ * for context switch tests
+ */
+ waitpid(pid, &status, 0);
+ if (WIFEXITED(status) == 0) {
+ fprintf(stderr, "worker exited unexpectedly\n");
+ return -1;
+ }
+ if (WEXITSTATUS(status) != 0) {
+ fprintf(stderr, "worker exited with error\n");
+ return -1;
+ }
+
+ ret = read(new_stdout[0], signed_vals, sizeof(struct signatures));
+ if (ret == -1) {
+ perror("read returned error");
+ return -1;
+ }
+
+ return 0;
+}
+
/* check that a corrupted PAC results in SIGSEGV */
TEST_SIGNAL(corrupt_pac, SIGSEGV)
{
@@ -79,5 +192,40 @@ TEST(pac_instructions_not_nop_generic)
ASSERT_NE(0, keyg) TH_LOG("keyg instructions did nothing");
}
+/*
+ * fork() does not change keys. Only exec() does so call a worker program.
+ * Its only job is to sign a value and report back the resutls
+ */
+TEST(exec_unique_keys)
+{
+ struct signatures new_keys;
+ struct signatures old_keys;
+ int ret;
+ int different = 0;
+ int nkeys = NKEYS;
+ unsigned long hwcaps = getauxval(AT_HWCAP);
+
+ /* generic and data key instructions are not in NOP space. This prevents a SIGILL */
+ ASSERT_NE(0, hwcaps & HWCAP_PACA) TH_LOG("PAUTH not enabled");
+ if (!(hwcaps & HWCAP_PACG)) {
+ TH_LOG("WARNING: Generic PAUTH not enabled. Skipping generic key checks");
+ nkeys = NKEYS - 1;
+ }
+
+ for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
+ ret = exec_sign_all(&new_keys, i);
+ ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
+
+ if (nkeys == NKEYS)
+ sign_all(&old_keys, i);
+ else
+ sign_specific(&old_keys, i);
+
+ different |= !are_same(&old_keys, &new_keys, nkeys);
+ }
+
+ ASSERT_EQ(1, different) TH_LOG("exec() did not change keys");
+}
+
TEST_HARNESS_MAIN
--
2.17.1
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