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551 lines
13 KiB
551 lines
13 KiB
// 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 (pr_info()) |
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* - function has external effects (pr_info()) |
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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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memset((void *)buf, remaining & 0xFF, sizeof(buf)); |
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pr_info("loop %d/%d ...\n", (int)buf[remaining % sizeof(buf)], |
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recur_count); |
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if (!remaining) |
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return 0; |
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else |
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return recursive_loop(remaining - 1); |
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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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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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} |
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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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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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} |
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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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} |
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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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} |
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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 |
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* anyway due to the double fault. |
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*/ |
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struct desc_struct d = { |
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.type = 3, /* expand-up, writable, accessed data */ |
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.p = 1, /* present */ |
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.d = 1, /* 32-bit */ |
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.g = 0, /* limit in bytes */ |
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.s = 1, /* not system */ |
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}; |
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local_irq_disable(); |
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write_gdt_entry(get_cpu_gdt_rw(smp_processor_id()), |
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GDT_ENTRY_TLS_MIN, &d, DESCTYPE_S); |
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/* |
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* Put our zero-limit segment in SS and then trigger a fault. The |
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* 4-byte access to (%esp) will fault with #SS, and the attempt to |
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* deliver the fault will recursively cause #SS and result in #DF. |
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* This whole process happens while NMIs and MCEs are blocked by the |
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* MOV SS window. This is nice because an NMI with an invalid SS |
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* would also double-fault, resulting in the NMI or MCE being lost. |
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*/ |
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asm volatile ("movw %0, %%ss; addl $0, (%%esp)" :: |
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"r" ((unsigned short)(GDT_ENTRY_TLS_MIN << 3))); |
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pr_err("FAIL: tried to double fault but didn't die\n"); |
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#else |
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pr_err("XFAIL: this test is ia32-only\n"); |
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#endif |
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} |
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#ifdef CONFIG_ARM64 |
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static noinline void change_pac_parameters(void) |
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{ |
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if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH)) { |
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/* Reset the keys of current task */ |
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ptrauth_thread_init_kernel(current); |
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ptrauth_thread_switch_kernel(current); |
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} |
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} |
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#endif |
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noinline void lkdtm_CORRUPT_PAC(void) |
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{ |
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#ifdef CONFIG_ARM64 |
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#define CORRUPT_PAC_ITERATE 10 |
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int i; |
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if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH)) |
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pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH\n"); |
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if (!system_supports_address_auth()) { |
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pr_err("FAIL: CPU lacks pointer authentication feature\n"); |
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return; |
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} |
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pr_info("changing PAC parameters to force function return failure...\n"); |
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/* |
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* PAC is a hash value computed from input keys, return address and |
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* stack pointer. As pac has fewer bits so there is a chance of |
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* collision, so iterate few times to reduce the collision probability. |
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*/ |
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for (i = 0; i < CORRUPT_PAC_ITERATE; i++) |
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change_pac_parameters(); |
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pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n"); |
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#else |
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pr_err("XFAIL: this test is arm64-only\n"); |
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#endif |
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} |
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void lkdtm_FORTIFY_OBJECT(void) |
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{ |
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struct target { |
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char a[10]; |
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} target[2] = {}; |
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int result; |
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/* |
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* Using volatile prevents the compiler from determining the value of |
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* 'size' at compile time. Without that, we would get a compile error |
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* rather than a runtime error. |
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*/ |
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volatile int size = 11; |
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pr_info("trying to read past the end of a struct\n"); |
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result = memcmp(&target[0], &target[1], size); |
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/* Print result to prevent the code from being eliminated */ |
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pr_err("FAIL: fortify did not catch an object overread!\n" |
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"\"%d\" was the memcmp result.\n", result); |
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} |
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void lkdtm_FORTIFY_SUBOBJECT(void) |
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{ |
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struct target { |
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char a[10]; |
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char b[10]; |
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} target; |
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char *src; |
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src = kmalloc(20, GFP_KERNEL); |
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strscpy(src, "over ten bytes", 20); |
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pr_info("trying to strcpy past the end of a member of a struct\n"); |
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/* |
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* strncpy(target.a, src, 20); will hit a compile error because the |
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* compiler knows at build time that target.a < 20 bytes. Use strcpy() |
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* to force a runtime error. |
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*/ |
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strcpy(target.a, src); |
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/* Use target.a to prevent the code from being eliminated */ |
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pr_err("FAIL: fortify did not catch an sub-object overrun!\n" |
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"\"%s\" was copied.\n", target.a); |
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kfree(src); |
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}
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