From: Boyan Karatotev boyan.karatotev@arm.com
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@kernel.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will@kernel.org Reviewed-by: Vincenzo Frascino Vincenzo.Frascino@arm.com Reviewed-by: Amit Daniel Kachhap amit.kachhap@arm.com Acked-by: Shuah Khan skhan@linuxfoundation.org Signed-off-by: Boyan Karatotev boyan.karatotev@arm.com --- tools/testing/selftests/arm64/pauth/Makefile | 4 + .../selftests/arm64/pauth/exec_target.c | 34 ++++ tools/testing/selftests/arm64/pauth/helper.h | 10 ++ tools/testing/selftests/arm64/pauth/pac.c | 150 ++++++++++++++++++ 4 files changed, 198 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 5c0dd129562f..72e290b0b10c 100644 --- a/tools/testing/selftests/arm64/pauth/Makefile +++ b/tools/testing/selftests/arm64/pauth/Makefile @@ -13,6 +13,7 @@ pauth_cc_support := $(shell if ($(CC) $(CFLAGS) -march=armv8.3-a -E -x c /dev/nu ifeq ($(pauth_cc_support),1) TEST_GEN_PROGS := pac TEST_GEN_FILES := pac_corruptor.o helper.o +TEST_GEN_PROGS_EXTENDED := exec_target endif
include ../../lib.mk @@ -30,6 +31,9 @@ $(OUTPUT)/helper.o: helper.c # greater, gcc emits pac* instructions which are not in HINT NOP space, # preventing the tests from occurring at all. Compile for ARMv8.2 so tests can # run on earlier targets and print a meaningful error messages +$(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 endif 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..4435600ca400 --- /dev/null +++ b/tools/testing/selftests/arm64/pauth/exec_target.c @@ -0,0 +1,34 @@ +// 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 35c4f3357ae3..652496c7b411 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);
/* PAuth sign a value with key ia and modifier value 0 */ diff --git a/tools/testing/selftests/arm64/pauth/pac.c b/tools/testing/selftests/arm64/pauth/pac.c index bd3d4c0eca9d..b363ad6a0b50 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 <setjmp.h>
@@ -28,6 +30,117 @@ do { \ ASSERT_NE(0, hwcaps & HWCAP_PACG) TH_LOG("Generic PAUTH not enabled"); \ } 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 n_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; +} + sigjmp_buf jmpbuf; void pac_signal_handler(int signum, siginfo_t *si, void *uc) { @@ -92,4 +205,41 @@ 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_changed_keys) +{ + struct signatures new_keys; + struct signatures old_keys; + int ret; + int same = 10; + 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); + + ret = n_same(&old_keys, &new_keys, nkeys); + if (ret < same) + same = ret; + } + + ASSERT_EQ(0, same) TH_LOG("exec() did not change %d keys", same); +} + TEST_HARNESS_MAIN