597 lines
15 KiB
C
597 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This is for all the tests related to logic bugs (e.g. bad dereferences,
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* bad alignment, bad loops, bad locking, bad scheduling, deep stacks, and
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* lockups) along with other things that don't fit well into existing LKDTM
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* test source files.
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*/
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#include "lkdtm.h"
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#include <linux/list.h>
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#include <linux/sched.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/task_stack.h>
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#include <linux/uaccess.h>
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#include <linux/slab.h>
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#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
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#include <asm/desc.h>
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#endif
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struct lkdtm_list {
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struct list_head node;
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};
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/*
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* Make sure our attempts to over run the kernel stack doesn't trigger
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* a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
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* recurse past the end of THREAD_SIZE by default.
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*/
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#if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
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#define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2)
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#else
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#define REC_STACK_SIZE (THREAD_SIZE / 8)
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#endif
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#define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)
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static int recur_count = REC_NUM_DEFAULT;
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static DEFINE_SPINLOCK(lock_me_up);
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/*
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* Make sure compiler does not optimize this function or stack frame away:
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* - function marked noinline
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* - stack variables are marked volatile
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* - stack variables are written (memset()) and read (buf[..] passed as arg)
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* - function may have external effects (memzero_explicit())
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* - no tail recursion possible
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*/
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static int noinline recursive_loop(int remaining)
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{
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volatile char buf[REC_STACK_SIZE];
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volatile int ret;
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memset((void *)buf, remaining & 0xFF, sizeof(buf));
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if (!remaining)
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ret = 0;
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else
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ret = recursive_loop((int)buf[remaining % sizeof(buf)] - 1);
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memzero_explicit((void *)buf, sizeof(buf));
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return ret;
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}
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/* If the depth is negative, use the default, otherwise keep parameter. */
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void __init lkdtm_bugs_init(int *recur_param)
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{
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if (*recur_param < 0)
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*recur_param = recur_count;
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else
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recur_count = *recur_param;
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}
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void lkdtm_PANIC(void)
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{
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panic("dumptest");
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}
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void lkdtm_BUG(void)
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{
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BUG();
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}
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static int warn_counter;
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void lkdtm_WARNING(void)
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{
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WARN_ON(++warn_counter);
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}
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void lkdtm_WARNING_MESSAGE(void)
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{
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WARN(1, "Warning message trigger count: %d\n", ++warn_counter);
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}
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void lkdtm_EXCEPTION(void)
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{
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*((volatile int *) 0) = 0;
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}
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void lkdtm_LOOP(void)
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{
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for (;;)
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;
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}
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void lkdtm_EXHAUST_STACK(void)
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{
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pr_info("Calling function with %lu frame size to depth %d ...\n",
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REC_STACK_SIZE, recur_count);
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recursive_loop(recur_count);
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pr_info("FAIL: survived without exhausting stack?!\n");
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}
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static noinline void __lkdtm_CORRUPT_STACK(void *stack)
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{
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memset(stack, '\xff', 64);
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}
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/* This should trip the stack canary, not corrupt the return address. */
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noinline void lkdtm_CORRUPT_STACK(void)
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{
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/* Use default char array length that triggers stack protection. */
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char data[8] __aligned(sizeof(void *));
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pr_info("Corrupting stack containing char array ...\n");
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__lkdtm_CORRUPT_STACK((void *)&data);
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}
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/* Same as above but will only get a canary with -fstack-protector-strong */
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noinline void lkdtm_CORRUPT_STACK_STRONG(void)
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{
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union {
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unsigned short shorts[4];
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unsigned long *ptr;
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} data __aligned(sizeof(void *));
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pr_info("Corrupting stack containing union ...\n");
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__lkdtm_CORRUPT_STACK((void *)&data);
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}
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static pid_t stack_pid;
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static unsigned long stack_addr;
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void lkdtm_REPORT_STACK(void)
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{
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volatile uintptr_t magic;
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pid_t pid = task_pid_nr(current);
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if (pid != stack_pid) {
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pr_info("Starting stack offset tracking for pid %d\n", pid);
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stack_pid = pid;
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stack_addr = (uintptr_t)&magic;
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}
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pr_info("Stack offset: %d\n", (int)(stack_addr - (uintptr_t)&magic));
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}
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static pid_t stack_canary_pid;
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static unsigned long stack_canary;
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static unsigned long stack_canary_offset;
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static noinline void __lkdtm_REPORT_STACK_CANARY(void *stack)
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{
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int i = 0;
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pid_t pid = task_pid_nr(current);
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unsigned long *canary = (unsigned long *)stack;
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unsigned long current_offset = 0, init_offset = 0;
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/* Do our best to find the canary in a 16 word window ... */
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for (i = 1; i < 16; i++) {
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canary = (unsigned long *)stack + i;
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#ifdef CONFIG_STACKPROTECTOR
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if (*canary == current->stack_canary)
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current_offset = i;
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if (*canary == init_task.stack_canary)
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init_offset = i;
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#endif
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}
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if (current_offset == 0) {
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/*
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* If the canary doesn't match what's in the task_struct,
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* we're either using a global canary or the stack frame
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* layout changed.
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*/
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if (init_offset != 0) {
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pr_err("FAIL: global stack canary found at offset %ld (canary for pid %d matches init_task's)!\n",
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init_offset, pid);
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} else {
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pr_warn("FAIL: did not correctly locate stack canary :(\n");
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pr_expected_config(CONFIG_STACKPROTECTOR);
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}
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return;
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} else if (init_offset != 0) {
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pr_warn("WARNING: found both current and init_task canaries nearby?!\n");
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}
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canary = (unsigned long *)stack + current_offset;
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if (stack_canary_pid == 0) {
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stack_canary = *canary;
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stack_canary_pid = pid;
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stack_canary_offset = current_offset;
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pr_info("Recorded stack canary for pid %d at offset %ld\n",
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stack_canary_pid, stack_canary_offset);
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} else if (pid == stack_canary_pid) {
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pr_warn("ERROR: saw pid %d again -- please use a new pid\n", pid);
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} else {
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if (current_offset != stack_canary_offset) {
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pr_warn("ERROR: canary offset changed from %ld to %ld!?\n",
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stack_canary_offset, current_offset);
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return;
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}
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if (*canary == stack_canary) {
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pr_warn("FAIL: canary identical for pid %d and pid %d at offset %ld!\n",
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stack_canary_pid, pid, current_offset);
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} else {
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pr_info("ok: stack canaries differ between pid %d and pid %d at offset %ld.\n",
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stack_canary_pid, pid, current_offset);
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/* Reset the test. */
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stack_canary_pid = 0;
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}
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}
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}
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void lkdtm_REPORT_STACK_CANARY(void)
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{
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/* Use default char array length that triggers stack protection. */
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char data[8] __aligned(sizeof(void *)) = { };
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__lkdtm_REPORT_STACK_CANARY((void *)&data);
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}
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void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)
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{
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static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5};
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u32 *p;
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u32 val = 0x12345678;
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p = (u32 *)(data + 1);
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if (*p == 0)
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val = 0x87654321;
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*p = val;
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if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
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pr_err("XFAIL: arch has CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS\n");
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}
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void lkdtm_SOFTLOCKUP(void)
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{
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preempt_disable();
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for (;;)
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cpu_relax();
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}
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void lkdtm_HARDLOCKUP(void)
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{
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local_irq_disable();
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for (;;)
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cpu_relax();
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}
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void lkdtm_SPINLOCKUP(void)
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{
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/* Must be called twice to trigger. */
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spin_lock(&lock_me_up);
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/* Let sparse know we intended to exit holding the lock. */
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__release(&lock_me_up);
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}
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void lkdtm_HUNG_TASK(void)
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{
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set_current_state(TASK_UNINTERRUPTIBLE);
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schedule();
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}
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volatile unsigned int huge = INT_MAX - 2;
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volatile unsigned int ignored;
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void lkdtm_OVERFLOW_SIGNED(void)
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{
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int value;
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value = huge;
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pr_info("Normal signed addition ...\n");
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value += 1;
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ignored = value;
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pr_info("Overflowing signed addition ...\n");
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value += 4;
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ignored = value;
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}
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void lkdtm_OVERFLOW_UNSIGNED(void)
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{
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unsigned int value;
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value = huge;
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pr_info("Normal unsigned addition ...\n");
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value += 1;
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ignored = value;
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pr_info("Overflowing unsigned addition ...\n");
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value += 4;
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ignored = value;
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}
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/* Intentionally using old-style flex array definition of 1 byte. */
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struct array_bounds_flex_array {
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int one;
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int two;
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char data[1];
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};
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struct array_bounds {
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int one;
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int two;
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char data[8];
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int three;
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};
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void lkdtm_ARRAY_BOUNDS(void)
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{
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struct array_bounds_flex_array *not_checked;
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struct array_bounds *checked;
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volatile int i;
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not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
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checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
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if (!not_checked || !checked) {
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kfree(not_checked);
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kfree(checked);
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return;
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}
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pr_info("Array access within bounds ...\n");
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/* For both, touch all bytes in the actual member size. */
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for (i = 0; i < sizeof(checked->data); i++)
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checked->data[i] = 'A';
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/*
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* For the uninstrumented flex array member, also touch 1 byte
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* beyond to verify it is correctly uninstrumented.
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*/
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for (i = 0; i < sizeof(not_checked->data) + 1; i++)
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not_checked->data[i] = 'A';
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pr_info("Array access beyond bounds ...\n");
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for (i = 0; i < sizeof(checked->data) + 1; i++)
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checked->data[i] = 'B';
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kfree(not_checked);
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kfree(checked);
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pr_err("FAIL: survived array bounds overflow!\n");
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if (IS_ENABLED(CONFIG_UBSAN_BOUNDS))
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pr_expected_config(CONFIG_UBSAN_TRAP);
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else
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pr_expected_config(CONFIG_UBSAN_BOUNDS);
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}
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void lkdtm_CORRUPT_LIST_ADD(void)
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{
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/*
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* Initially, an empty list via LIST_HEAD:
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* test_head.next = &test_head
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* test_head.prev = &test_head
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*/
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LIST_HEAD(test_head);
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struct lkdtm_list good, bad;
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void *target[2] = { };
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void *redirection = ⌖
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pr_info("attempting good list addition\n");
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/*
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* Adding to the list performs these actions:
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* test_head.next->prev = &good.node
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* good.node.next = test_head.next
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* good.node.prev = test_head
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* test_head.next = good.node
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*/
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list_add(&good.node, &test_head);
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pr_info("attempting corrupted list addition\n");
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/*
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* In simulating this "write what where" primitive, the "what" is
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* the address of &bad.node, and the "where" is the address held
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* by "redirection".
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*/
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test_head.next = redirection;
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list_add(&bad.node, &test_head);
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if (target[0] == NULL && target[1] == NULL)
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pr_err("Overwrite did not happen, but no BUG?!\n");
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else {
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pr_err("list_add() corruption not detected!\n");
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pr_expected_config(CONFIG_DEBUG_LIST);
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}
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}
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void lkdtm_CORRUPT_LIST_DEL(void)
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{
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LIST_HEAD(test_head);
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struct lkdtm_list item;
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void *target[2] = { };
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void *redirection = ⌖
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list_add(&item.node, &test_head);
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pr_info("attempting good list removal\n");
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list_del(&item.node);
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pr_info("attempting corrupted list removal\n");
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list_add(&item.node, &test_head);
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/* As with the list_add() test above, this corrupts "next". */
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item.node.next = redirection;
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list_del(&item.node);
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if (target[0] == NULL && target[1] == NULL)
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pr_err("Overwrite did not happen, but no BUG?!\n");
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else {
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pr_err("list_del() corruption not detected!\n");
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pr_expected_config(CONFIG_DEBUG_LIST);
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}
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}
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/* Test that VMAP_STACK is actually allocating with a leading guard page */
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void lkdtm_STACK_GUARD_PAGE_LEADING(void)
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{
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const unsigned char *stack = task_stack_page(current);
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const unsigned char *ptr = stack - 1;
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volatile unsigned char byte;
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pr_info("attempting bad read from page below current stack\n");
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byte = *ptr;
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pr_err("FAIL: accessed page before stack! (byte: %x)\n", byte);
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}
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/* Test that VMAP_STACK is actually allocating with a trailing guard page */
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void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
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{
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const unsigned char *stack = task_stack_page(current);
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const unsigned char *ptr = stack + THREAD_SIZE;
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volatile unsigned char byte;
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pr_info("attempting bad read from page above current stack\n");
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byte = *ptr;
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pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte);
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}
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void lkdtm_UNSET_SMEP(void)
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{
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#if IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_UML)
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#define MOV_CR4_DEPTH 64
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void (*direct_write_cr4)(unsigned long val);
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unsigned char *insn;
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unsigned long cr4;
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int i;
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cr4 = native_read_cr4();
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if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) {
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pr_err("FAIL: SMEP not in use\n");
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return;
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}
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cr4 &= ~(X86_CR4_SMEP);
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pr_info("trying to clear SMEP normally\n");
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native_write_cr4(cr4);
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if (cr4 == native_read_cr4()) {
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pr_err("FAIL: pinning SMEP failed!\n");
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cr4 |= X86_CR4_SMEP;
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pr_info("restoring SMEP\n");
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native_write_cr4(cr4);
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return;
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}
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pr_info("ok: SMEP did not get cleared\n");
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/*
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* To test the post-write pinning verification we need to call
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* directly into the middle of native_write_cr4() where the
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* cr4 write happens, skipping any pinning. This searches for
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* the cr4 writing instruction.
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*/
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insn = (unsigned char *)native_write_cr4;
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for (i = 0; i < MOV_CR4_DEPTH; i++) {
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/* mov %rdi, %cr4 */
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if (insn[i] == 0x0f && insn[i+1] == 0x22 && insn[i+2] == 0xe7)
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break;
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/* mov %rdi,%rax; mov %rax, %cr4 */
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if (insn[i] == 0x48 && insn[i+1] == 0x89 &&
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insn[i+2] == 0xf8 && insn[i+3] == 0x0f &&
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insn[i+4] == 0x22 && insn[i+5] == 0xe0)
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break;
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}
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if (i >= MOV_CR4_DEPTH) {
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pr_info("ok: cannot locate cr4 writing call gadget\n");
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return;
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}
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direct_write_cr4 = (void *)(insn + i);
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pr_info("trying to clear SMEP with call gadget\n");
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direct_write_cr4(cr4);
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if (native_read_cr4() & X86_CR4_SMEP) {
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pr_info("ok: SMEP removal was reverted\n");
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} else {
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pr_err("FAIL: cleared SMEP not detected!\n");
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cr4 |= X86_CR4_SMEP;
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pr_info("restoring SMEP\n");
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native_write_cr4(cr4);
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}
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#else
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pr_err("XFAIL: this test is x86_64-only\n");
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#endif
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}
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void lkdtm_DOUBLE_FAULT(void)
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{
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#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
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/*
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* Trigger #DF by setting the stack limit to zero. This clobbers
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|
* 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
|
|
}
|