![Arnd Bergmann](/assets/img/avatar_default.png)
After the latest change to make sure the compiler actually does a memset,
it is now smart enough to flag the stack overflow at compile time,
at least with gcc-7.0:
drivers/misc/lkdtm_bugs.c: In function 'lkdtm_CORRUPT_STACK':
drivers/misc/lkdtm_bugs.c:88:144: warning: 'memset' writing 64 bytes into a region of size 8 overflows the destination [-Wstringop-overflow=]
To outsmart the compiler again, this moves the memset into a noinline
function where (for now) it doesn't see that we intentionally write
broken code here.
Fixes: c55d240003
("lkdtm: Prevent the compiler from optimising lkdtm_CORRUPT_STACK()")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
223 lines
4.5 KiB
C
223 lines
4.5 KiB
C
/*
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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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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 (CONFIG_FRAME_WARN / 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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static int recursive_loop(int remaining)
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{
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char buf[REC_STACK_SIZE];
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/* Make sure compiler does not optimize this away. */
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memset(buf, (remaining & 0xff) | 0x1, REC_STACK_SIZE);
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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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void lkdtm_WARNING(void)
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{
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WARN_ON(1);
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}
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void lkdtm_EXCEPTION(void)
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{
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*((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_OVERFLOW(void)
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{
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(void) recursive_loop(recur_count);
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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, 'a', 64);
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}
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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];
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__lkdtm_CORRUPT_STACK(&data);
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pr_info("Corrupted stack with '%16s'...\n", 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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}
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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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void lkdtm_ATOMIC_UNDERFLOW(void)
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{
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atomic_t under = ATOMIC_INIT(INT_MIN);
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pr_info("attempting good atomic increment\n");
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atomic_inc(&under);
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atomic_dec(&under);
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pr_info("attempting bad atomic underflow\n");
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atomic_dec(&under);
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}
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void lkdtm_ATOMIC_OVERFLOW(void)
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{
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atomic_t over = ATOMIC_INIT(INT_MAX);
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pr_info("attempting good atomic decrement\n");
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atomic_dec(&over);
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atomic_inc(&over);
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pr_info("attempting bad atomic overflow\n");
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atomic_inc(&over);
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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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