diff options
Diffstat (limited to 'drivers/misc/lkdtm/usercopy.c')
| -rw-r--r-- | drivers/misc/lkdtm/usercopy.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c index 9725aed305bb..b0e020372d11 100644 --- a/drivers/misc/lkdtm/usercopy.c +++ b/drivers/misc/lkdtm/usercopy.c @@ -30,12 +30,12 @@ static const unsigned char test_text[] = "This is a test.\n"; */ static noinline unsigned char *trick_compiler(unsigned char *stack) { - return stack + 0; + return stack + unconst; } static noinline unsigned char *do_usercopy_stack_callee(int value) { - unsigned char buf[32]; + unsigned char buf[128]; int i; /* Exercise stack to avoid everything living in registers. */ @@ -43,7 +43,12 @@ static noinline unsigned char *do_usercopy_stack_callee(int value) buf[i] = value & 0xff; } - return trick_compiler(buf); + /* + * Put the target buffer in the middle of stack allocation + * so that we don't step on future stack users regardless + * of stack growth direction. + */ + return trick_compiler(&buf[(128/2)-32]); } static noinline void do_usercopy_stack(bool to_user, bool bad_frame) @@ -66,6 +71,12 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame) bad_stack -= sizeof(unsigned long); } +#ifdef ARCH_HAS_CURRENT_STACK_POINTER + pr_info("stack : %px\n", (void *)current_stack_pointer); +#endif + pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack)); + pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack)); + user_addr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, 0); |