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lkdtm: various fixes

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- Move KERNEL_DS test to non-canonical range
 - Make stack exhaustion test more robust
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 Comment: Kees Cook <kees@outflux.net>
 
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Merge tag 'lkdtm-next' of https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux into char-misc-linus

Kees writes:

lkdtm: various fixes

- Move KERNEL_DS test to non-canonical range
- Make stack exhaustion test more robust

* tag 'lkdtm-next' of https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  lkdtm/bugs: Adjust recursion test to avoid elision
  lkdtm/usercopy: Moves the KERNEL_DS test to non-canonical
This commit is contained in:
Greg Kroah-Hartman 2019-05-24 20:30:04 +02:00
commit 02bd610e85
4 changed files with 27 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

23
drivers/misc/lkdtm/bugs.c
View file

@ -32,12 +32,20 @@ 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 (pr_info())
* - function has external effects (pr_info())
* */
static int noinline recursive_loop(int remaining)
{
char buf[REC_STACK_SIZE];
volatile char buf[REC_STACK_SIZE];
/* Make sure compiler does not optimize this away. */
memset(buf, (remaining & 0xff) | 0x1, REC_STACK_SIZE);
memset((void *)buf, remaining & 0xFF, sizeof(buf));
pr_info("loop %d/%d ...\n", (int)buf[remaining % sizeof(buf)],
recur_count);
if (!remaining)
return 0;
else
@ -81,9 +89,12 @@ void lkdtm_LOOP(void)
;
}
void lkdtm_OVERFLOW(void)
void lkdtm_EXHAUST_STACK(void)
{
(void) recursive_loop(recur_count);
pr_info("Calling function with %d 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)

6
drivers/misc/lkdtm/core.c
View file

@ -119,12 +119,12 @@ static const struct crashtype crashtypes[] = {
CRASHTYPE(WARNING),
CRASHTYPE(EXCEPTION),
CRASHTYPE(LOOP),
CRASHTYPE(OVERFLOW),
CRASHTYPE(EXHAUST_STACK),
CRASHTYPE(CORRUPT_STACK),
CRASHTYPE(CORRUPT_STACK_STRONG),
CRASHTYPE(CORRUPT_LIST_ADD),
CRASHTYPE(CORRUPT_LIST_DEL),
CRASHTYPE(CORRUPT_USER_DS),
CRASHTYPE(CORRUPT_STACK),
CRASHTYPE(CORRUPT_STACK_STRONG),
CRASHTYPE(STACK_GUARD_PAGE_LEADING),
CRASHTYPE(STACK_GUARD_PAGE_TRAILING),
CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),

2
drivers/misc/lkdtm/lkdtm.h
View file

@ -13,7 +13,7 @@ void lkdtm_BUG(void);
void lkdtm_WARNING(void);
void lkdtm_EXCEPTION(void);
void lkdtm_LOOP(void);
void lkdtm_OVERFLOW(void);
void lkdtm_EXHAUST_STACK(void);
void lkdtm_CORRUPT_STACK(void);
void lkdtm_CORRUPT_STACK_STRONG(void);
void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void);

10
drivers/misc/lkdtm/usercopy.c
View file

@ -324,14 +324,16 @@ void lkdtm_USERCOPY_KERNEL(void)
void lkdtm_USERCOPY_KERNEL_DS(void)
{
char __user *user_ptr = (char __user *)ERR_PTR(-EINVAL);
char __user *user_ptr =
(char __user *)(0xFUL << (sizeof(unsigned long) * 8 - 4));
mm_segment_t old_fs = get_fs();
char buf[10] = {0};
pr_info("attempting copy_to_user on unmapped kernel address\n");
pr_info("attempting copy_to_user() to noncanonical address: %px\n",
user_ptr);
set_fs(KERNEL_DS);
if (copy_to_user(user_ptr, buf, sizeof(buf)))
pr_info("copy_to_user un unmapped kernel address failed\n");
if (copy_to_user(user_ptr, buf, sizeof(buf)) == 0)
pr_err("copy_to_user() to noncanonical address succeeded!?\n");
set_fs(old_fs);
}