| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * This is for all the tests related to logic bugs (e.g. bad dereferences, |
| * bad alignment, bad loops, bad locking, bad scheduling, deep stacks, and |
| * lockups) along with other things that don't fit well into existing LKDTM |
| * test source files. |
| */ |
| #include "lkdtm.h" |
| #include <linux/list.h> |
| #include <linux/sched.h> |
| #include <linux/sched/signal.h> |
| #include <linux/sched/task_stack.h> |
| #include <linux/uaccess.h> |
| #include <linux/slab.h> |
| |
| #if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML) |
| #include <asm/desc.h> |
| #endif |
| |
| struct lkdtm_list { |
| struct list_head node; |
| }; |
| |
| /* |
| * Make sure our attempts to over run the kernel stack doesn't trigger |
| * a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we |
| * recurse past the end of THREAD_SIZE by default. |
| */ |
| #if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0) |
| #define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2) |
| #else |
| #define REC_STACK_SIZE (THREAD_SIZE / 8) |
| #endif |
| #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2) |
| |
| static int recur_count = REC_NUM_DEFAULT; |
| |
| static DEFINE_SPINLOCK(lock_me_up); |
| |
| /* |
| * Make sure compiler does not optimize this function or stack frame away: |
| * - function marked noinline |
| * - stack variables are marked volatile |
| * - stack variables are written (memset()) and read (pr_info()) |
| * - function has external effects (pr_info()) |
| * */ |
| static int noinline recursive_loop(int remaining) |
| { |
| volatile char buf[REC_STACK_SIZE]; |
| |
| memset((void *)buf, remaining & 0xFF, sizeof(buf)); |
| pr_info("loop %d/%d ...\n", (int)buf[remaining % sizeof(buf)], |
| recur_count); |
| if (!remaining) |
| return 0; |
| else |
| return recursive_loop(remaining - 1); |
| } |
| |
| /* If the depth is negative, use the default, otherwise keep parameter. */ |
| void __init lkdtm_bugs_init(int *recur_param) |
| { |
| if (*recur_param < 0) |
| *recur_param = recur_count; |
| else |
| recur_count = *recur_param; |
| } |
| |
| void lkdtm_PANIC(void) |
| { |
| panic("dumptest"); |
| } |
| |
| void lkdtm_BUG(void) |
| { |
| BUG(); |
| } |
| |
| static int warn_counter; |
| |
| void lkdtm_WARNING(void) |
| { |
| WARN_ON(++warn_counter); |
| } |
| |
| void lkdtm_WARNING_MESSAGE(void) |
| { |
| WARN(1, "Warning message trigger count: %d\n", ++warn_counter); |
| } |
| |
| void lkdtm_EXCEPTION(void) |
| { |
| *((volatile int *) 0) = 0; |
| } |
| |
| void lkdtm_LOOP(void) |
| { |
| for (;;) |
| ; |
| } |
| |
| void lkdtm_EXHAUST_STACK(void) |
| { |
| pr_info("Calling function with %lu frame size to depth %d ...\n", |
| REC_STACK_SIZE, recur_count); |
| recursive_loop(recur_count); |
| pr_info("FAIL: survived without exhausting stack?!\n"); |
| } |
| |
| static noinline void __lkdtm_CORRUPT_STACK(void *stack) |
| { |
| memset(stack, '\xff', 64); |
| } |
| |
| /* This should trip the stack canary, not corrupt the return address. */ |
| noinline void lkdtm_CORRUPT_STACK(void) |
| { |
| /* Use default char array length that triggers stack protection. */ |
| char data[8] __aligned(sizeof(void *)); |
| |
| pr_info("Corrupting stack containing char array ...\n"); |
| __lkdtm_CORRUPT_STACK((void *)&data); |
| } |
| |
| /* Same as above but will only get a canary with -fstack-protector-strong */ |
| noinline void lkdtm_CORRUPT_STACK_STRONG(void) |
| { |
| union { |
| unsigned short shorts[4]; |
| unsigned long *ptr; |
| } data __aligned(sizeof(void *)); |
| |
| pr_info("Corrupting stack containing union ...\n"); |
| __lkdtm_CORRUPT_STACK((void *)&data); |
| } |
| |
| static pid_t stack_pid; |
| static unsigned long stack_addr; |
| |
| void lkdtm_REPORT_STACK(void) |
| { |
| volatile uintptr_t magic; |
| pid_t pid = task_pid_nr(current); |
| |
| if (pid != stack_pid) { |
| pr_info("Starting stack offset tracking for pid %d\n", pid); |
| stack_pid = pid; |
| stack_addr = (uintptr_t)&magic; |
| } |
| |
| pr_info("Stack offset: %d\n", (int)(stack_addr - (uintptr_t)&magic)); |
| } |
| |
| void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void) |
| { |
| static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5}; |
| u32 *p; |
| u32 val = 0x12345678; |
| |
| p = (u32 *)(data + 1); |
| if (*p == 0) |
| val = 0x87654321; |
| *p = val; |
| |
| if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) |
| pr_err("XFAIL: arch has CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS\n"); |
| } |
| |
| void lkdtm_SOFTLOCKUP(void) |
| { |
| preempt_disable(); |
| for (;;) |
| cpu_relax(); |
| } |
| |
| void lkdtm_HARDLOCKUP(void) |
| { |
| local_irq_disable(); |
| for (;;) |
| cpu_relax(); |
| } |
| |
| void lkdtm_SPINLOCKUP(void) |
| { |
| /* Must be called twice to trigger. */ |
| spin_lock(&lock_me_up); |
| /* Let sparse know we intended to exit holding the lock. */ |
| __release(&lock_me_up); |
| } |
| |
| void lkdtm_HUNG_TASK(void) |
| { |
| set_current_state(TASK_UNINTERRUPTIBLE); |
| schedule(); |
| } |
| |
| volatile unsigned int huge = INT_MAX - 2; |
| volatile unsigned int ignored; |
| |
| void lkdtm_OVERFLOW_SIGNED(void) |
| { |
| int value; |
| |
| value = huge; |
| pr_info("Normal signed addition ...\n"); |
| value += 1; |
| ignored = value; |
| |
| pr_info("Overflowing signed addition ...\n"); |
| value += 4; |
| ignored = value; |
| } |
| |
| |
| void lkdtm_OVERFLOW_UNSIGNED(void) |
| { |
| unsigned int value; |
| |
| value = huge; |
| pr_info("Normal unsigned addition ...\n"); |
| value += 1; |
| ignored = value; |
| |
| pr_info("Overflowing unsigned addition ...\n"); |
| value += 4; |
| ignored = value; |
| } |
| |
| /* Intentionally using old-style flex array definition of 1 byte. */ |
| struct array_bounds_flex_array { |
| int one; |
| int two; |
| char data[1]; |
| }; |
| |
| struct array_bounds { |
| int one; |
| int two; |
| char data[8]; |
| int three; |
| }; |
| |
| void lkdtm_ARRAY_BOUNDS(void) |
| { |
| struct array_bounds_flex_array *not_checked; |
| struct array_bounds *checked; |
| volatile int i; |
| |
| not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL); |
| checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL); |
| |
| pr_info("Array access within bounds ...\n"); |
| /* For both, touch all bytes in the actual member size. */ |
| for (i = 0; i < sizeof(checked->data); i++) |
| checked->data[i] = 'A'; |
| /* |
| * For the uninstrumented flex array member, also touch 1 byte |
| * beyond to verify it is correctly uninstrumented. |
| */ |
| for (i = 0; i < sizeof(not_checked->data) + 1; i++) |
| not_checked->data[i] = 'A'; |
| |
| pr_info("Array access beyond bounds ...\n"); |
| for (i = 0; i < sizeof(checked->data) + 1; i++) |
| checked->data[i] = 'B'; |
| |
| kfree(not_checked); |
| kfree(checked); |
| pr_err("FAIL: survived array bounds overflow!\n"); |
| pr_expected_config(CONFIG_UBSAN_BOUNDS); |
| } |
| |
| void lkdtm_CORRUPT_LIST_ADD(void) |
| { |
| /* |
| * Initially, an empty list via LIST_HEAD: |
| * test_head.next = &test_head |
| * test_head.prev = &test_head |
| */ |
| LIST_HEAD(test_head); |
| struct lkdtm_list good, bad; |
| void *target[2] = { }; |
| void *redirection = ⌖ |
| |
| pr_info("attempting good list addition\n"); |
| |
| /* |
| * Adding to the list performs these actions: |
| * test_head.next->prev = &good.node |
| * good.node.next = test_head.next |
| * good.node.prev = test_head |
| * test_head.next = good.node |
| */ |
| list_add(&good.node, &test_head); |
| |
| pr_info("attempting corrupted list addition\n"); |
| /* |
| * In simulating this "write what where" primitive, the "what" is |
| * the address of &bad.node, and the "where" is the address held |
| * by "redirection". |
| */ |
| test_head.next = redirection; |
| list_add(&bad.node, &test_head); |
| |
| if (target[0] == NULL && target[1] == NULL) |
| pr_err("Overwrite did not happen, but no BUG?!\n"); |
| else { |
| pr_err("list_add() corruption not detected!\n"); |
| pr_expected_config(CONFIG_DEBUG_LIST); |
| } |
| } |
| |
| void lkdtm_CORRUPT_LIST_DEL(void) |
| { |
| LIST_HEAD(test_head); |
| struct lkdtm_list item; |
| void *target[2] = { }; |
| void *redirection = ⌖ |
| |
| list_add(&item.node, &test_head); |
| |
| pr_info("attempting good list removal\n"); |
| list_del(&item.node); |
| |
| pr_info("attempting corrupted list removal\n"); |
| list_add(&item.node, &test_head); |
| |
| /* As with the list_add() test above, this corrupts "next". */ |
| item.node.next = redirection; |
| list_del(&item.node); |
| |
| if (target[0] == NULL && target[1] == NULL) |
| pr_err("Overwrite did not happen, but no BUG?!\n"); |
| else { |
| pr_err("list_del() corruption not detected!\n"); |
| pr_expected_config(CONFIG_DEBUG_LIST); |
| } |
| } |
| |
| /* Test that VMAP_STACK is actually allocating with a leading guard page */ |
| void lkdtm_STACK_GUARD_PAGE_LEADING(void) |
| { |
| const unsigned char *stack = task_stack_page(current); |
| const unsigned char *ptr = stack - 1; |
| volatile unsigned char byte; |
| |
| pr_info("attempting bad read from page below current stack\n"); |
| |
| byte = *ptr; |
| |
| pr_err("FAIL: accessed page before stack! (byte: %x)\n", byte); |
| } |
| |
| /* Test that VMAP_STACK is actually allocating with a trailing guard page */ |
| void lkdtm_STACK_GUARD_PAGE_TRAILING(void) |
| { |
| const unsigned char *stack = task_stack_page(current); |
| const unsigned char *ptr = stack + THREAD_SIZE; |
| volatile unsigned char byte; |
| |
| pr_info("attempting bad read from page above current stack\n"); |
| |
| byte = *ptr; |
| |
| pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte); |
| } |
| |
| void lkdtm_UNSET_SMEP(void) |
| { |
| #if IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_UML) |
| #define MOV_CR4_DEPTH 64 |
| void (*direct_write_cr4)(unsigned long val); |
| unsigned char *insn; |
| unsigned long cr4; |
| int i; |
| |
| cr4 = native_read_cr4(); |
| |
| if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) { |
| pr_err("FAIL: SMEP not in use\n"); |
| return; |
| } |
| cr4 &= ~(X86_CR4_SMEP); |
| |
| pr_info("trying to clear SMEP normally\n"); |
| native_write_cr4(cr4); |
| if (cr4 == native_read_cr4()) { |
| pr_err("FAIL: pinning SMEP failed!\n"); |
| cr4 |= X86_CR4_SMEP; |
| pr_info("restoring SMEP\n"); |
| native_write_cr4(cr4); |
| return; |
| } |
| pr_info("ok: SMEP did not get cleared\n"); |
| |
| /* |
| * To test the post-write pinning verification we need to call |
| * directly into the middle of native_write_cr4() where the |
| * cr4 write happens, skipping any pinning. This searches for |
| * the cr4 writing instruction. |
| */ |
| insn = (unsigned char *)native_write_cr4; |
| for (i = 0; i < MOV_CR4_DEPTH; i++) { |
| /* mov %rdi, %cr4 */ |
| if (insn[i] == 0x0f && insn[i+1] == 0x22 && insn[i+2] == 0xe7) |
| break; |
| /* mov %rdi,%rax; mov %rax, %cr4 */ |
| if (insn[i] == 0x48 && insn[i+1] == 0x89 && |
| insn[i+2] == 0xf8 && insn[i+3] == 0x0f && |
| insn[i+4] == 0x22 && insn[i+5] == 0xe0) |
| break; |
| } |
| if (i >= MOV_CR4_DEPTH) { |
| pr_info("ok: cannot locate cr4 writing call gadget\n"); |
| return; |
| } |
| direct_write_cr4 = (void *)(insn + i); |
| |
| pr_info("trying to clear SMEP with call gadget\n"); |
| direct_write_cr4(cr4); |
| if (native_read_cr4() & X86_CR4_SMEP) { |
| pr_info("ok: SMEP removal was reverted\n"); |
| } else { |
| pr_err("FAIL: cleared SMEP not detected!\n"); |
| cr4 |= X86_CR4_SMEP; |
| pr_info("restoring SMEP\n"); |
| native_write_cr4(cr4); |
| } |
| #else |
| pr_err("XFAIL: this test is x86_64-only\n"); |
| #endif |
| } |
| |
| void lkdtm_DOUBLE_FAULT(void) |
| { |
| #if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML) |
| /* |
| * Trigger #DF by setting the stack limit to zero. This clobbers |
| * a GDT TLS slot, which is okay because the current task will die |
| * anyway due to the double fault. |
| */ |
| struct desc_struct d = { |
| .type = 3, /* expand-up, writable, accessed data */ |
| .p = 1, /* present */ |
| .d = 1, /* 32-bit */ |
| .g = 0, /* limit in bytes */ |
| .s = 1, /* not system */ |
| }; |
| |
| local_irq_disable(); |
| write_gdt_entry(get_cpu_gdt_rw(smp_processor_id()), |
| GDT_ENTRY_TLS_MIN, &d, DESCTYPE_S); |
| |
| /* |
| * Put our zero-limit segment in SS and then trigger a fault. The |
| * 4-byte access to (%esp) will fault with #SS, and the attempt to |
| * deliver the fault will recursively cause #SS and result in #DF. |
| * This whole process happens while NMIs and MCEs are blocked by the |
| * MOV SS window. This is nice because an NMI with an invalid SS |
| * would also double-fault, resulting in the NMI or MCE being lost. |
| */ |
| asm volatile ("movw %0, %%ss; addl $0, (%%esp)" :: |
| "r" ((unsigned short)(GDT_ENTRY_TLS_MIN << 3))); |
| |
| pr_err("FAIL: tried to double fault but didn't die\n"); |
| #else |
| pr_err("XFAIL: this test is ia32-only\n"); |
| #endif |
| } |
| |
| #ifdef CONFIG_ARM64 |
| static noinline void change_pac_parameters(void) |
| { |
| if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL)) { |
| /* Reset the keys of current task */ |
| ptrauth_thread_init_kernel(current); |
| ptrauth_thread_switch_kernel(current); |
| } |
| } |
| #endif |
| |
| noinline void lkdtm_CORRUPT_PAC(void) |
| { |
| #ifdef CONFIG_ARM64 |
| #define CORRUPT_PAC_ITERATE 10 |
| int i; |
| |
| if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL)) |
| pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH_KERNEL\n"); |
| |
| if (!system_supports_address_auth()) { |
| pr_err("FAIL: CPU lacks pointer authentication feature\n"); |
| return; |
| } |
| |
| pr_info("changing PAC parameters to force function return failure...\n"); |
| /* |
| * PAC is a hash value computed from input keys, return address and |
| * stack pointer. As pac has fewer bits so there is a chance of |
| * collision, so iterate few times to reduce the collision probability. |
| */ |
| for (i = 0; i < CORRUPT_PAC_ITERATE; i++) |
| change_pac_parameters(); |
| |
| pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n"); |
| #else |
| pr_err("XFAIL: this test is arm64-only\n"); |
| #endif |
| } |