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lkdtm: Test VMAP_STACK allocates leading/trailing guard pages 

Two new tests STACK_GUARD_PAGE_LEADING and STACK_GUARD_PAGE_TRAILING
attempt to read the byte before and after, respectively, of the current
stack frame, which should fault.

Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2017-08-04 13:04:21 -07:00
parent c7fea48876
commit 7b25a85c9d
3 changed files with 34 additions and 0 deletions
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2
drivers/misc/lkdtm.h
View File

@ -22,6 +22,8 @@ void lkdtm_HUNG_TASK(void);
void lkdtm_CORRUPT_LIST_ADD(void);
void lkdtm_CORRUPT_LIST_DEL(void);
void lkdtm_CORRUPT_USER_DS(void);
void lkdtm_STACK_GUARD_PAGE_LEADING(void);
void lkdtm_STACK_GUARD_PAGE_TRAILING(void);
/* lkdtm_heap.c */
void lkdtm_OVERWRITE_ALLOCATION(void);

30
drivers/misc/lkdtm_bugs.c
View File

@ -8,6 +8,7 @@
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
#include <linux/uaccess.h>
struct lkdtm_list {
@ -199,6 +200,7 @@ void lkdtm_CORRUPT_LIST_DEL(void)
pr_err("list_del() corruption not detected!\n");
}
/* Test if unbalanced set_fs(KERNEL_DS)/set_fs(USER_DS) check exists. */
void lkdtm_CORRUPT_USER_DS(void)
{
pr_info("setting bad task size limit\n");
@ -207,3 +209,31 @@ void lkdtm_CORRUPT_USER_DS(void)
/* Make sure we do not keep running with a KERNEL_DS! */
force_sig(SIGKILL, current);
}
/* Test that VMAP_STACK is actually allocating with a leading guard page */
void lkdtm_STACK_GUARD_PAGE_LEADING(void)
{
const unsigned char *stack = task_stack_page(current);
const unsigned char *ptr = stack - 1;
volatile unsigned char byte;
pr_info("attempting bad read from page below current stack\n");
byte = *ptr;
pr_err("FAIL: accessed page before stack!\n");
}
/* Test that VMAP_STACK is actually allocating with a trailing guard page */
void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
{
const unsigned char *stack = task_stack_page(current);
const unsigned char *ptr = stack + THREAD_SIZE;
volatile unsigned char byte;
pr_info("attempting bad read from page above current stack\n");
byte = *ptr;
pr_err("FAIL: accessed page after stack!\n");
}

2
drivers/misc/lkdtm_core.c
View File

@ -201,6 +201,8 @@ struct crashtype crashtypes[] = {
CRASHTYPE(CORRUPT_LIST_DEL),
CRASHTYPE(CORRUPT_USER_DS),
CRASHTYPE(CORRUPT_STACK),
CRASHTYPE(STACK_GUARD_PAGE_LEADING),
CRASHTYPE(STACK_GUARD_PAGE_TRAILING),
CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
CRASHTYPE(OVERWRITE_ALLOCATION),
CRASHTYPE(WRITE_AFTER_FREE),