diff options
Diffstat (limited to 'tools/testing/selftests/syscall_user_dispatch/sud_test.c')
| -rw-r--r-- | tools/testing/selftests/syscall_user_dispatch/sud_test.c | 380 |
1 files changed, 380 insertions, 0 deletions
diff --git a/tools/testing/selftests/syscall_user_dispatch/sud_test.c b/tools/testing/selftests/syscall_user_dispatch/sud_test.c new file mode 100644 index 000000000000..b855c6000287 --- /dev/null +++ b/tools/testing/selftests/syscall_user_dispatch/sud_test.c @@ -0,0 +1,380 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (c) 2020 Collabora Ltd. + * + * Test code for syscall user dispatch + */ + +#define _GNU_SOURCE +#include <sys/prctl.h> +#include <sys/sysinfo.h> +#include <sys/syscall.h> +#include <signal.h> +#include <stdbool.h> +#include <stdlib.h> + +#include <asm/unistd.h> +#include "kselftest_harness.h" + +#ifndef PR_SET_SYSCALL_USER_DISPATCH +# define PR_SET_SYSCALL_USER_DISPATCH 59 +# define PR_SYS_DISPATCH_OFF 0 +# define SYSCALL_DISPATCH_FILTER_ALLOW 0 +# define SYSCALL_DISPATCH_FILTER_BLOCK 1 +#endif + +#ifndef PR_SYS_DISPATCH_EXCLUSIVE_ON +# define PR_SYS_DISPATCH_EXCLUSIVE_ON 1 +# define PR_SYS_DISPATCH_INCLUSIVE_ON 2 +#endif + +#ifndef SYS_USER_DISPATCH +# define SYS_USER_DISPATCH 2 +#endif + +#ifdef __NR_syscalls +# define MAGIC_SYSCALL_1 (__NR_syscalls + 1) /* Bad Linux syscall number */ +#else +# define MAGIC_SYSCALL_1 (0xff00) /* Bad Linux syscall number */ +#endif + +#define SYSCALL_DISPATCH_ON(x) ((x) = SYSCALL_DISPATCH_FILTER_BLOCK) +#define SYSCALL_DISPATCH_OFF(x) ((x) = SYSCALL_DISPATCH_FILTER_ALLOW) + +/* Test Summary: + * + * - dispatch_trigger_sigsys: Verify if PR_SET_SYSCALL_USER_DISPATCH is + * able to trigger SIGSYS on a syscall. + * + * - bad_selector: Test that a bad selector value triggers SIGSYS with + * si_errno EINVAL. + * + * - bad_prctl_param: Test that the API correctly rejects invalid + * parameters on prctl + * + * - dispatch_and_return: Test that a syscall is selectively dispatched + * to userspace depending on the value of selector. + * + * - disable_dispatch: Test that the PR_SYS_DISPATCH_OFF correctly + * disables the dispatcher + * + * - direct_dispatch_range: Test that a syscall within the allowed range + * can bypass the dispatcher. + */ + +TEST_SIGNAL(dispatch_trigger_sigsys, SIGSYS) +{ + char sel = SYSCALL_DISPATCH_FILTER_ALLOW; + struct sysinfo info; + int ret; + + ret = sysinfo(&info); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_EXCLUSIVE_ON, 0, 0, &sel); + ASSERT_EQ(0, ret) { + TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH"); + } + + SYSCALL_DISPATCH_ON(sel); + + sysinfo(&info); + + EXPECT_FALSE(true) { + TH_LOG("Unreachable!"); + } +} + +static void prctl_valid(struct __test_metadata *_metadata, + unsigned long op, unsigned long off, + unsigned long size, void *sel) +{ + EXPECT_EQ(0, prctl(PR_SET_SYSCALL_USER_DISPATCH, op, off, size, sel)); +} + +static void prctl_invalid(struct __test_metadata *_metadata, + unsigned long op, unsigned long off, + unsigned long size, void *sel, int err) +{ + EXPECT_EQ(-1, prctl(PR_SET_SYSCALL_USER_DISPATCH, op, off, size, sel)); + EXPECT_EQ(err, errno); +} + +TEST(bad_prctl_param) +{ + char sel = SYSCALL_DISPATCH_FILTER_ALLOW; + int op; + + /* Invalid op */ + op = -1; + prctl_invalid(_metadata, op, 0, 0, &sel, EINVAL); + + /* PR_SYS_DISPATCH_OFF */ + op = PR_SYS_DISPATCH_OFF; + + /* offset != 0 */ + prctl_invalid(_metadata, op, 0x1, 0x0, 0, EINVAL); + + /* len != 0 */ + prctl_invalid(_metadata, op, 0x0, 0xff, 0, EINVAL); + + /* sel != NULL */ + prctl_invalid(_metadata, op, 0x0, 0x0, &sel, EINVAL); + + /* Valid parameter */ + prctl_valid(_metadata, op, 0x0, 0x0, 0x0); + + /* PR_SYS_DISPATCH_EXCLUSIVE_ON */ + op = PR_SYS_DISPATCH_EXCLUSIVE_ON; + + /* Dispatcher region is bad (offset > 0 && len == 0) */ + prctl_invalid(_metadata, op, 0x1, 0x0, &sel, EINVAL); + prctl_invalid(_metadata, op, -1L, 0x0, &sel, EINVAL); + + /* Invalid selector */ + prctl_invalid(_metadata, op, 0x0, 0x1, (void *) -1, EFAULT); + + /* + * Dispatcher range overflows unsigned long + */ + prctl_invalid(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, 1, -1L, &sel, EINVAL); + + /* + * Allowed range overflows usigned long + */ + prctl_invalid(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, -1L, 0x1, &sel, EINVAL); + + /* 0 len should fail for PR_SYS_DISPATCH_INCLUSIVE_ON */ + prctl_invalid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, 1, 0, 0, EINVAL); + + /* Range wrap-around should fail */ + prctl_invalid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, -1L, 2, 0, EINVAL); + + /* Normal range shouldn't fail */ + prctl_valid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, 2, 3, 0); + + /* Invalid selector */ + prctl_invalid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, 2, 3, (void *) -1, EFAULT); +} + +/* + * Use global selector for handle_sigsys tests, to avoid passing + * selector to signal handler + */ +char glob_sel; +int nr_syscalls_emulated; +int si_code; +int si_errno; +unsigned long syscall_addr; + +static void handle_sigsys(int sig, siginfo_t *info, void *ucontext) +{ + si_code = info->si_code; + si_errno = info->si_errno; + syscall_addr = (unsigned long)info->si_call_addr; + + if (info->si_syscall == MAGIC_SYSCALL_1) + nr_syscalls_emulated++; + + /* In preparation for sigreturn. */ + SYSCALL_DISPATCH_OFF(glob_sel); + + /* + * The tests for argument handling assume that `syscall(x) == x`. This + * is a NOP on x86 because the syscall number is passed in %rax, which + * happens to also be the function ABI return register. Other + * architectures may need to swizzle the arguments around. + */ +#if defined(__riscv) +/* REG_A7 is not defined in libc headers */ +# define REG_A7 (REG_A0 + 7) + + ((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A0] = + ((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A7]; +#endif +} + +int setup_sigsys_handler(void) +{ + struct sigaction act; + sigset_t mask; + + memset(&act, 0, sizeof(act)); + sigemptyset(&mask); + act.sa_sigaction = handle_sigsys; + act.sa_flags = SA_SIGINFO; + act.sa_mask = mask; + return sigaction(SIGSYS, &act, NULL); +} + +TEST(dispatch_and_return) +{ + long ret; + + glob_sel = 0; + nr_syscalls_emulated = 0; + si_code = 0; + si_errno = 0; + + ASSERT_EQ(0, setup_sigsys_handler()); + + /* Make sure selector is good prior to prctl. */ + SYSCALL_DISPATCH_OFF(glob_sel); + + ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_EXCLUSIVE_ON, 0, 0, &glob_sel); + ASSERT_EQ(0, ret) { + TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH"); + } + + /* MAGIC_SYSCALL_1 doesn't exist. */ + SYSCALL_DISPATCH_OFF(glob_sel); + ret = syscall(MAGIC_SYSCALL_1); + EXPECT_EQ(-1, ret) { + TH_LOG("Dispatch triggered unexpectedly"); + } + + /* MAGIC_SYSCALL_1 should be emulated. */ + nr_syscalls_emulated = 0; + SYSCALL_DISPATCH_ON(glob_sel); + + ret = syscall(MAGIC_SYSCALL_1); + EXPECT_EQ(MAGIC_SYSCALL_1, ret) { + TH_LOG("Failed to intercept syscall"); + } + EXPECT_EQ(1, nr_syscalls_emulated) { + TH_LOG("Failed to emulate syscall"); + } + ASSERT_EQ(SYS_USER_DISPATCH, si_code) { + TH_LOG("Bad si_code in SIGSYS"); + } + ASSERT_EQ(0, si_errno) { + TH_LOG("Bad si_errno in SIGSYS"); + } +} + +TEST_SIGNAL(bad_selector, SIGSYS) +{ + long ret; + struct sigaction act; + sigset_t mask; + struct sysinfo info; + + glob_sel = SYSCALL_DISPATCH_FILTER_ALLOW; + nr_syscalls_emulated = 0; + si_code = 0; + si_errno = 0; + + memset(&act, 0, sizeof(act)); + sigemptyset(&mask); + + act.sa_sigaction = handle_sigsys; + act.sa_flags = SA_SIGINFO; + act.sa_mask = mask; + + ret = sigaction(SIGSYS, &act, NULL); + ASSERT_EQ(0, ret); + + /* Make sure selector is good prior to prctl. */ + SYSCALL_DISPATCH_OFF(glob_sel); + + ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_EXCLUSIVE_ON, 0, 0, &glob_sel); + ASSERT_EQ(0, ret) { + TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH"); + } + + glob_sel = -1; + + sysinfo(&info); + + /* Even though it is ready to catch SIGSYS, the signal is + * supposed to be uncatchable. + */ + + EXPECT_FALSE(true) { + TH_LOG("Unreachable!"); + } +} + +TEST(disable_dispatch) +{ + int ret; + struct sysinfo info; + char sel = 0; + + ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_EXCLUSIVE_ON, 0, 0, &sel); + ASSERT_EQ(0, ret) { + TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH"); + } + + /* MAGIC_SYSCALL_1 doesn't exist. */ + SYSCALL_DISPATCH_OFF(glob_sel); + + ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_OFF, 0, 0, 0); + EXPECT_EQ(0, ret) { + TH_LOG("Failed to unset syscall user dispatch"); + } + + /* Shouldn't have any effect... */ + SYSCALL_DISPATCH_ON(glob_sel); + + ret = syscall(__NR_sysinfo, &info); + EXPECT_EQ(0, ret) { + TH_LOG("Dispatch triggered unexpectedly"); + } +} + +TEST(direct_dispatch_range) +{ + int ret = 0; + struct sysinfo info; + char sel = SYSCALL_DISPATCH_FILTER_ALLOW; + + /* + * Instead of calculating libc addresses; allow the entire + * memory map and lock the selector. + */ + ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_EXCLUSIVE_ON, 0, -1L, &sel); + ASSERT_EQ(0, ret) { + TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH"); + } + + SYSCALL_DISPATCH_ON(sel); + + ret = sysinfo(&info); + ASSERT_EQ(0, ret) { + TH_LOG("Dispatch triggered unexpectedly"); + } +} + +static void test_range(struct __test_metadata *_metadata, + unsigned long op, unsigned long off, + unsigned long size, bool dispatch) +{ + nr_syscalls_emulated = 0; + SYSCALL_DISPATCH_OFF(glob_sel); + EXPECT_EQ(0, prctl(PR_SET_SYSCALL_USER_DISPATCH, op, off, size, &glob_sel)); + SYSCALL_DISPATCH_ON(glob_sel); + if (dispatch) { + EXPECT_EQ(syscall(MAGIC_SYSCALL_1), MAGIC_SYSCALL_1); + EXPECT_EQ(nr_syscalls_emulated, 1); + } else { + EXPECT_EQ(syscall(MAGIC_SYSCALL_1), -1); + EXPECT_EQ(nr_syscalls_emulated, 0); + } +} + +TEST(dispatch_range) +{ + ASSERT_EQ(0, setup_sigsys_handler()); + test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, 0, 0, true); + test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr, 1, false); + test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr-100, 200, false); + test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr+1, 100, true); + test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr-100, 100, true); + test_range(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, syscall_addr, 1, true); + test_range(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, syscall_addr-1, 1, false); + test_range(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, syscall_addr+1, 1, false); + SYSCALL_DISPATCH_OFF(glob_sel); +} + +TEST_HARNESS_MAIN |