diff options
Diffstat (limited to 'drivers/misc/lkdtm/bugs.c')
| -rw-r--r-- | drivers/misc/lkdtm/bugs.c | 566 |
1 files changed, 520 insertions, 46 deletions
diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index 7eebbdfbcacd..376047beea3d 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -6,12 +6,19 @@ * test source files. */ #include "lkdtm.h" +#include <linux/cpu.h> #include <linux/list.h> #include <linux/sched.h> #include <linux/sched/signal.h> #include <linux/sched/task_stack.h> +#include <linux/slab.h> +#include <linux/stop_machine.h> #include <linux/uaccess.h> +#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML) +#include <asm/desc.h> +#endif + struct lkdtm_list { struct list_head node; }; @@ -22,9 +29,9 @@ struct lkdtm_list { * recurse past the end of THREAD_SIZE by default. */ #if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0) -#define REC_STACK_SIZE (CONFIG_FRAME_WARN / 2) +#define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2) #else -#define REC_STACK_SIZE (THREAD_SIZE / 8) +#define REC_STACK_SIZE (THREAD_SIZE / 8UL) #endif #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2) @@ -32,16 +39,26 @@ static int recur_count = REC_NUM_DEFAULT; static DEFINE_SPINLOCK(lock_me_up); -static int recursive_loop(int remaining) +/* + * 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 (buf[..] passed as arg) + * - function may have external effects (memzero_explicit()) + * - no tail recursion possible + */ +static int noinline recursive_loop(int remaining) { - char buf[REC_STACK_SIZE]; + volatile char buf[REC_STACK_SIZE]; + volatile int ret; - /* Make sure compiler does not optimize this away. */ - memset(buf, (remaining & 0xff) | 0x1, REC_STACK_SIZE); + memset((void *)buf, remaining & 0xFF, sizeof(buf)); if (!remaining) - return 0; + ret = 0; else - return recursive_loop(remaining - 1); + ret = recursive_loop((int)buf[remaining % sizeof(buf)] - 1); + memzero_explicit((void *)buf, sizeof(buf)); + return ret; } /* If the depth is negative, use the default, otherwise keep parameter. */ @@ -53,37 +70,70 @@ void __init lkdtm_bugs_init(int *recur_param) recur_count = *recur_param; } -void lkdtm_PANIC(void) +static void lkdtm_PANIC(void) { panic("dumptest"); } -void lkdtm_BUG(void) +static int panic_stop_irqoff_fn(void *arg) +{ + atomic_t *v = arg; + + /* + * As stop_machine() disables interrupts, all CPUs within this function + * have interrupts disabled and cannot take a regular IPI. + * + * The last CPU which enters here will trigger a panic, and as all CPUs + * cannot take a regular IPI, we'll only be able to stop secondaries if + * smp_send_stop() or crash_smp_send_stop() uses an NMI. + */ + if (atomic_inc_return(v) == num_online_cpus()) + panic("panic stop irqoff test"); + + for (;;) + cpu_relax(); +} + +static void lkdtm_PANIC_STOP_IRQOFF(void) +{ + atomic_t v = ATOMIC_INIT(0); + stop_machine(panic_stop_irqoff_fn, &v, cpu_online_mask); +} + +static void lkdtm_BUG(void) { BUG(); } static int warn_counter; -void lkdtm_WARNING(void) +static void lkdtm_WARNING(void) { - WARN(1, "Warning message trigger count: %d\n", warn_counter++); + WARN_ON(++warn_counter); } -void lkdtm_EXCEPTION(void) +static void lkdtm_WARNING_MESSAGE(void) +{ + WARN(1, "Warning message trigger count: %d\n", ++warn_counter); +} + +static void lkdtm_EXCEPTION(void) { *((volatile int *) 0) = 0; } -void lkdtm_LOOP(void) +static void lkdtm_LOOP(void) { for (;;) ; } -void lkdtm_OVERFLOW(void) +static void lkdtm_EXHAUST_STACK(void) { - (void) recursive_loop(recur_count); + 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) @@ -92,30 +142,122 @@ static noinline void __lkdtm_CORRUPT_STACK(void *stack) } /* This should trip the stack canary, not corrupt the return address. */ -noinline void lkdtm_CORRUPT_STACK(void) +static noinline void lkdtm_CORRUPT_STACK(void) { /* Use default char array length that triggers stack protection. */ char data[8] __aligned(sizeof(void *)); - __lkdtm_CORRUPT_STACK(&data); - - pr_info("Corrupted stack containing char array ...\n"); + 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) +static noinline void lkdtm_CORRUPT_STACK_STRONG(void) { union { unsigned short shorts[4]; unsigned long *ptr; } data __aligned(sizeof(void *)); - __lkdtm_CORRUPT_STACK(&data); + pr_info("Corrupting stack containing union ...\n"); + __lkdtm_CORRUPT_STACK((void *)&data); +} + +static pid_t stack_pid; +static unsigned long stack_addr; + +static 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)); +} + +static pid_t stack_canary_pid; +static unsigned long stack_canary; +static unsigned long stack_canary_offset; + +static noinline void __lkdtm_REPORT_STACK_CANARY(void *stack) +{ + int i = 0; + pid_t pid = task_pid_nr(current); + unsigned long *canary = (unsigned long *)stack; + unsigned long current_offset = 0, init_offset = 0; + + /* Do our best to find the canary in a 16 word window ... */ + for (i = 1; i < 16; i++) { + canary = (unsigned long *)stack + i; +#ifdef CONFIG_STACKPROTECTOR + if (*canary == current->stack_canary) + current_offset = i; + if (*canary == init_task.stack_canary) + init_offset = i; +#endif + } + + if (current_offset == 0) { + /* + * If the canary doesn't match what's in the task_struct, + * we're either using a global canary or the stack frame + * layout changed. + */ + if (init_offset != 0) { + pr_err("FAIL: global stack canary found at offset %ld (canary for pid %d matches init_task's)!\n", + init_offset, pid); + } else { + pr_warn("FAIL: did not correctly locate stack canary :(\n"); + pr_expected_config(CONFIG_STACKPROTECTOR); + } + + return; + } else if (init_offset != 0) { + pr_warn("WARNING: found both current and init_task canaries nearby?!\n"); + } + + canary = (unsigned long *)stack + current_offset; + if (stack_canary_pid == 0) { + stack_canary = *canary; + stack_canary_pid = pid; + stack_canary_offset = current_offset; + pr_info("Recorded stack canary for pid %d at offset %ld\n", + stack_canary_pid, stack_canary_offset); + } else if (pid == stack_canary_pid) { + pr_warn("ERROR: saw pid %d again -- please use a new pid\n", pid); + } else { + if (current_offset != stack_canary_offset) { + pr_warn("ERROR: canary offset changed from %ld to %ld!?\n", + stack_canary_offset, current_offset); + return; + } + + if (*canary == stack_canary) { + pr_warn("FAIL: canary identical for pid %d and pid %d at offset %ld!\n", + stack_canary_pid, pid, current_offset); + } else { + pr_info("ok: stack canaries differ between pid %d and pid %d at offset %ld.\n", + stack_canary_pid, pid, current_offset); + /* Reset the test. */ + stack_canary_pid = 0; + } + } +} + +static void lkdtm_REPORT_STACK_CANARY(void) +{ + /* Use default char array length that triggers stack protection. */ + char data[8] __aligned(sizeof(void *)) = { }; - pr_info("Corrupted stack containing union ...\n"); + __lkdtm_REPORT_STACK_CANARY((void *)&data); } -void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void) +static void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void) { static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5}; u32 *p; @@ -125,23 +267,55 @@ void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void) 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) +static void lkdtm_SOFTLOCKUP(void) { preempt_disable(); for (;;) cpu_relax(); } -void lkdtm_HARDLOCKUP(void) +static void lkdtm_HARDLOCKUP(void) { local_irq_disable(); for (;;) cpu_relax(); } -void lkdtm_SPINLOCKUP(void) +static void __lkdtm_SMP_CALL_LOCKUP(void *unused) +{ + for (;;) + cpu_relax(); +} + +static void lkdtm_SMP_CALL_LOCKUP(void) +{ + unsigned int cpu, target; + + cpus_read_lock(); + + cpu = get_cpu(); + target = cpumask_any_but(cpu_online_mask, cpu); + + if (target >= nr_cpu_ids) { + pr_err("FAIL: no other online CPUs\n"); + goto out_put_cpus; + } + + smp_call_function_single(target, __lkdtm_SMP_CALL_LOCKUP, NULL, 1); + + pr_err("FAIL: did not hang\n"); + +out_put_cpus: + put_cpu(); + cpus_read_unlock(); +} + +static void lkdtm_SPINLOCKUP(void) { /* Must be called twice to trigger. */ spin_lock(&lock_me_up); @@ -149,13 +323,138 @@ void lkdtm_SPINLOCKUP(void) __release(&lock_me_up); } -void lkdtm_HUNG_TASK(void) +static void __noreturn lkdtm_HUNG_TASK(void) { set_current_state(TASK_UNINTERRUPTIBLE); schedule(); + BUG(); +} + +static volatile unsigned int huge = INT_MAX - 2; +static volatile unsigned int ignored; + +static 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; +} + + +static 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 unannotated flex array definition. */ +struct array_bounds_flex_array { + int one; + int two; + char data[]; +}; + +struct array_bounds { + int one; + int two; + char data[8]; + int three; +}; + +static 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); + if (!not_checked || !checked) { + kfree(not_checked); + kfree(checked); + return; + } + + 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 < 2; 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"); + if (IS_ENABLED(CONFIG_UBSAN_BOUNDS)) + pr_expected_config(CONFIG_UBSAN_TRAP); + else + pr_expected_config(CONFIG_UBSAN_BOUNDS); } -void lkdtm_CORRUPT_LIST_ADD(void) +struct lkdtm_annotated { + unsigned long flags; + int count; + int array[] __counted_by(count); +}; + +static volatile int fam_count = 4; + +static void lkdtm_FAM_BOUNDS(void) +{ + struct lkdtm_annotated *inst; + + inst = kzalloc(struct_size(inst, array, fam_count + 1), GFP_KERNEL); + if (!inst) { + pr_err("FAIL: could not allocate test struct!\n"); + return; + } + + inst->count = fam_count; + pr_info("Array access within bounds ...\n"); + inst->array[1] = fam_count; + ignored = inst->array[1]; + + pr_info("Array access beyond bounds ...\n"); + inst->array[fam_count] = fam_count; + ignored = inst->array[fam_count]; + + kfree(inst); + + pr_err("FAIL: survived access of invalid flexible array member index!\n"); + + if (!IS_ENABLED(CONFIG_CC_HAS_COUNTED_BY)) + pr_warn("This is expected since this %s was built with a compiler that does not support __counted_by\n", + lkdtm_kernel_info); + else if (IS_ENABLED(CONFIG_UBSAN_BOUNDS)) + pr_expected_config(CONFIG_UBSAN_TRAP); + else + pr_expected_config(CONFIG_UBSAN_BOUNDS); +} + +static void lkdtm_CORRUPT_LIST_ADD(void) { /* * Initially, an empty list via LIST_HEAD: @@ -189,11 +488,13 @@ void lkdtm_CORRUPT_LIST_ADD(void) if (target[0] == NULL && target[1] == NULL) pr_err("Overwrite did not happen, but no BUG?!\n"); - else + else { pr_err("list_add() corruption not detected!\n"); + pr_expected_config(CONFIG_LIST_HARDENED); + } } -void lkdtm_CORRUPT_LIST_DEL(void) +static void lkdtm_CORRUPT_LIST_DEL(void) { LIST_HEAD(test_head); struct lkdtm_list item; @@ -214,22 +515,14 @@ void lkdtm_CORRUPT_LIST_DEL(void) if (target[0] == NULL && target[1] == NULL) pr_err("Overwrite did not happen, but no BUG?!\n"); - else + else { pr_err("list_del() corruption not detected!\n"); -} - -/* Test if unbalanced set_fs(KERNEL_DS)/set_fs(USER_DS) check exists. */ -void lkdtm_CORRUPT_USER_DS(void) -{ - pr_info("setting bad task size limit\n"); - set_fs(KERNEL_DS); - - /* Make sure we do not keep running with a KERNEL_DS! */ - force_sig(SIGKILL, current); + pr_expected_config(CONFIG_LIST_HARDENED); + } } /* Test that VMAP_STACK is actually allocating with a leading guard page */ -void lkdtm_STACK_GUARD_PAGE_LEADING(void) +static void lkdtm_STACK_GUARD_PAGE_LEADING(void) { const unsigned char *stack = task_stack_page(current); const unsigned char *ptr = stack - 1; @@ -239,11 +532,11 @@ void lkdtm_STACK_GUARD_PAGE_LEADING(void) byte = *ptr; - pr_err("FAIL: accessed page before stack!\n"); + 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) +static void lkdtm_STACK_GUARD_PAGE_TRAILING(void) { const unsigned char *stack = task_stack_page(current); const unsigned char *ptr = stack + THREAD_SIZE; @@ -253,5 +546,186 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(void) byte = *ptr; - pr_err("FAIL: accessed page after stack!\n"); + pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte); +} + +static 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; + OPTIMIZER_HIDE_VAR(insn); + 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 +} + +static 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 + +static 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 +} + +static struct crashtype crashtypes[] = { + CRASHTYPE(PANIC), + CRASHTYPE(PANIC_STOP_IRQOFF), + CRASHTYPE(BUG), + CRASHTYPE(WARNING), + CRASHTYPE(WARNING_MESSAGE), + CRASHTYPE(EXCEPTION), + CRASHTYPE(LOOP), + CRASHTYPE(EXHAUST_STACK), + CRASHTYPE(CORRUPT_STACK), + CRASHTYPE(CORRUPT_STACK_STRONG), + CRASHTYPE(REPORT_STACK), + CRASHTYPE(REPORT_STACK_CANARY), + CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE), + CRASHTYPE(SOFTLOCKUP), + CRASHTYPE(HARDLOCKUP), + CRASHTYPE(SMP_CALL_LOCKUP), + CRASHTYPE(SPINLOCKUP), + CRASHTYPE(HUNG_TASK), + CRASHTYPE(OVERFLOW_SIGNED), + CRASHTYPE(OVERFLOW_UNSIGNED), + CRASHTYPE(ARRAY_BOUNDS), + CRASHTYPE(FAM_BOUNDS), + CRASHTYPE(CORRUPT_LIST_ADD), + CRASHTYPE(CORRUPT_LIST_DEL), + CRASHTYPE(STACK_GUARD_PAGE_LEADING), + CRASHTYPE(STACK_GUARD_PAGE_TRAILING), + CRASHTYPE(UNSET_SMEP), + CRASHTYPE(DOUBLE_FAULT), + CRASHTYPE(CORRUPT_PAC), +}; + +struct crashtype_category bugs_crashtypes = { + .crashtypes = crashtypes, + .len = ARRAY_SIZE(crashtypes), +}; |
