* Re: [PATCH 2/2] lib: Introduce test_stackinit module
[not found] ` <20190212180441.15340-3-keescook@chromium.org>
@ 2019-03-11 10:52 ` Geert Uytterhoeven
2019-04-23 22:42 ` Kees Cook
0 siblings, 1 reply; 2+ messages in thread
From: Geert Uytterhoeven @ 2019-03-11 10:52 UTC (permalink / raw)
To: Kees Cook
Cc: Linux Kernel Mailing List, Emese Revfy, Alexander Popov,
Ard Biesheuvel, Laura Abbott, Jann Horn, Alexander Potapenko,
kernel-hardening, Linux/m68k
Hi Kees,
On Tue, Feb 12, 2019 at 7:08 PM Kees Cook <keescook@chromium.org> wrote:
> Adds test for stack initialization coverage. We have several build options
> that control the level of stack variable initialization. This test lets us
> visualize which options cover which cases, and provide tests for some of
> the pathological padding conditions the compiler will sometimes fail to
> initialize.
With current upstream, using gcc Ubuntu 8.2.0-1ubuntu2~18.04, I get
on m68k:
test_stackinit: u8_zero: stack fill missed target!?
test_stackinit: u8_zero: fill 1 wide
test_stackinit: u8_zero: target offset by 20
test_stackinit: u16_zero: stack fill missed target!?
test_stackinit: u16_zero: fill 2 wide
test_stackinit: u16_zero: target offset by 20
test_stackinit: u32_zero: stack fill missed target!?
test_stackinit: u32_zero: fill 4 wide
test_stackinit: u32_zero: target offset by 20
test_stackinit: u64_zero: stack fill missed target!?
test_stackinit: u64_zero: fill 8 wide
test_stackinit: u64_zero: target offset by 20
test_stackinit: char_array_zero: stack fill missed target!?
test_stackinit: char_array_zero: fill 16 wide
test_stackinit: char_array_zero: target offset by -12
test_stackinit: small_hole_zero: stack fill missed target!?
test_stackinit: small_hole_zero: fill 14 wide
test_stackinit: small_hole_zero: target offset by -12
test_stackinit: big_hole_zero ok
test_stackinit: trailing_hole_zero: stack fill missed target!?
test_stackinit: trailing_hole_zero: fill 14 wide
test_stackinit: trailing_hole_zero: target offset by -12
test_stackinit: packed_zero: stack fill missed target!?
test_stackinit: packed_zero: fill 16 wide
test_stackinit: packed_zero: target offset by -12
test_stackinit: small_hole_dynamic_partial: stack fill missed target!?
test_stackinit: small_hole_dynamic_partial: fill 14 wide
test_stackinit: small_hole_dynamic_partial: target offset by -12
test_stackinit: big_hole_dynamic_partial ok
test_stackinit: trailing_hole_dynamic_partial: stack fill missed target!?
test_stackinit: trailing_hole_dynamic_partial: fill 14 wide
test_stackinit: trailing_hole_dynamic_partial: target offset by -12
test_stackinit: packed_dynamic_partial: stack fill missed target!?
test_stackinit: packed_dynamic_partial: fill 16 wide
test_stackinit: packed_dynamic_partial: target offset by -12
test_stackinit: small_hole_static_partial: stack fill missed target!?
test_stackinit: small_hole_static_partial: fill 14 wide
test_stackinit: small_hole_static_partial: target offset by -12
test_stackinit: big_hole_static_partial ok
test_stackinit: trailing_hole_static_partial: stack fill missed target!?
test_stackinit: trailing_hole_static_partial: fill 14 wide
test_stackinit: trailing_hole_static_partial: target offset by -12
test_stackinit: packed_static_partial: stack fill missed target!?
test_stackinit: packed_static_partial: fill 16 wide
test_stackinit: packed_static_partial: target offset by -12
test_stackinit: small_hole_static_all: stack fill missed target!?
test_stackinit: small_hole_static_all: fill 14 wide
test_stackinit: small_hole_static_all: target offset by -12
test_stackinit: big_hole_static_all FAIL (uninit bytes: 61)
test_stackinit: trailing_hole_static_all: stack fill missed target!?
test_stackinit: trailing_hole_static_all: fill 14 wide
test_stackinit: trailing_hole_static_all: target offset by -12
test_stackinit: packed_static_all: stack fill missed target!?
test_stackinit: packed_static_all: fill 16 wide
test_stackinit: packed_static_all: target offset by -12
test_stackinit: small_hole_dynamic_all: stack fill missed target!?
test_stackinit: small_hole_dynamic_all: fill 14 wide
test_stackinit: small_hole_dynamic_all: target offset by -12
test_stackinit: big_hole_dynamic_all FAIL (uninit bytes: 61)
test_stackinit: trailing_hole_dynamic_all: stack fill missed target!?
test_stackinit: trailing_hole_dynamic_all: fill 14 wide
test_stackinit: trailing_hole_dynamic_all: target offset by -12
test_stackinit: packed_dynamic_all: stack fill missed target!?
test_stackinit: packed_dynamic_all: fill 16 wide
test_stackinit: packed_dynamic_all: target offset by -12
test_stackinit: small_hole_runtime_partial: stack fill missed target!?
test_stackinit: small_hole_runtime_partial: fill 14 wide
test_stackinit: small_hole_runtime_partial: target offset by -12
test_stackinit: big_hole_runtime_partial FAIL (uninit bytes: 127)
test_stackinit: trailing_hole_runtime_partial: stack fill missed target!?
test_stackinit: trailing_hole_runtime_partial: fill 14 wide
test_stackinit: trailing_hole_runtime_partial: target offset by -12
test_stackinit: packed_runtime_partial: stack fill missed target!?
test_stackinit: packed_runtime_partial: fill 16 wide
test_stackinit: packed_runtime_partial: target offset by -12
test_stackinit: small_hole_runtime_all: stack fill missed target!?
test_stackinit: small_hole_runtime_all: fill 14 wide
test_stackinit: small_hole_runtime_all: target offset by -12
test_stackinit: big_hole_runtime_all FAIL (uninit bytes: 61)
test_stackinit: trailing_hole_runtime_all: stack fill missed target!?
test_stackinit: trailing_hole_runtime_all: fill 14 wide
test_stackinit: trailing_hole_runtime_all: target offset by -12
test_stackinit: packed_runtime_all: stack fill missed target!?
test_stackinit: packed_runtime_all: fill 16 wide
test_stackinit: packed_runtime_all: target offset by -12
test_stackinit: u8_none: stack fill missed target!?
test_stackinit: u8_none: fill 1 wide
test_stackinit: u8_none: target offset by 20
test_stackinit: u16_none: stack fill missed target!?
test_stackinit: u16_none: fill 2 wide
test_stackinit: u16_none: target offset by 20
test_stackinit: u32_none: stack fill missed target!?
test_stackinit: u32_none: fill 4 wide
test_stackinit: u32_none: target offset by 20
test_stackinit: u64_none: stack fill missed target!?
test_stackinit: u64_none: fill 8 wide
test_stackinit: u64_none: target offset by 20
test_stackinit: char_array_none: stack fill missed target!?
test_stackinit: char_array_none: fill 16 wide
test_stackinit: char_array_none: target offset by -12
test_stackinit: switch_1_none: stack fill missed target!?
test_stackinit: switch_1_none: fill 8 wide
test_stackinit: switch_1_none: target offset by 16
test_stackinit: switch_2_none: stack fill missed target!?
test_stackinit: switch_2_none: fill 8 wide
test_stackinit: switch_2_none: target offset by 16
test_stackinit: small_hole_none: stack fill missed target!?
test_stackinit: small_hole_none: fill 14 wide
test_stackinit: small_hole_none: target offset by -12
test_stackinit: big_hole_none FAIL (uninit bytes: 128)
test_stackinit: trailing_hole_none: stack fill missed target!?
test_stackinit: trailing_hole_none: fill 14 wide
test_stackinit: trailing_hole_none: target offset by -12
test_stackinit: packed_none: stack fill missed target!?
test_stackinit: packed_none: fill 16 wide
test_stackinit: packed_none: target offset by -12
test_stackinit: user: stack fill missed target!?
test_stackinit: user: fill 14 wide
test_stackinit: user: target offset by -12
test_stackinit: failures: 42
Any idea what is wrong? I find the test code a bit hard to understand...
Also, I see comments making assumptions that are not true:
struct test_small_hole {
size_t one;
char two;
/* 3 byte padding hole here. */
int three;
unsigned long four;
};
On m68k (and a few other architectures), integrals of 16-bit and larger
are aligned to a 2-byte address, so the padding may be only a single byte.
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH 2/2] lib: Introduce test_stackinit module
2019-03-11 10:52 ` [PATCH 2/2] lib: Introduce test_stackinit module Geert Uytterhoeven
@ 2019-04-23 22:42 ` Kees Cook
0 siblings, 0 replies; 2+ messages in thread
From: Kees Cook @ 2019-04-23 22:42 UTC (permalink / raw)
To: Geert Uytterhoeven
Cc: Linux Kernel Mailing List, Emese Revfy, Alexander Popov,
Ard Biesheuvel, Laura Abbott, Jann Horn, Alexander Potapenko,
Kernel Hardening, Linux/m68k
On Mon, Mar 11, 2019 at 3:52 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Kees,
>
> On Tue, Feb 12, 2019 at 7:08 PM Kees Cook <keescook@chromium.org> wrote:
> > Adds test for stack initialization coverage. We have several build options
> > that control the level of stack variable initialization. This test lets us
> > visualize which options cover which cases, and provide tests for some of
> > the pathological padding conditions the compiler will sometimes fail to
> > initialize.
>
> With current upstream, using gcc Ubuntu 8.2.0-1ubuntu2~18.04, I get
> on m68k:
Thanks for testing this on other architectures!
> test_stackinit: u8_zero: stack fill missed target!?
Hmpf. That's frustrating. That implies that the leaf function is
assembled in such a way that the "leaking" memory address and the
"controlled" memory address on the stack end up in different
locations. I had a lot of problems with this before I unified my leaf
function. I wonder if some inlining is happening with the m68k
compiler that I haven't accounted for?
> Any idea what is wrong? I find the test code a bit hard to understand...
Yeah, there was a lot of repetition, so I tried to save my sanity and
build macros. The particular problem above is with the "test_..."'s
call of the "leaf_..." functions:
/* Fill stack with 0xFF. */ \
ignored = leaf_ ##name((unsigned long)&ignored, 1, \
FETCH_ARG_ ## which(zero)); \
/* Clear entire check buffer for later bit tests. */ \
memset(check_buf, 0x00, sizeof(check_buf)); \
/* Extract stack-defined variable contents. */ \
ignored = leaf_ ##name((unsigned long)&ignored, 0, \
FETCH_ARG_ ## which(zero)); \
those two leaf_* invocations should produce stack variables at the
same location on the stack:
var_type var INIT_ ## which ## _ ## init_level; \
\
target_start = &var; \
target_size = sizeof(var); \
/* \
* Keep this buffer around to make sure we've got a \
* stack frame of SOME kind... \
*/ \
memset(buf, (char)(sp && 0xff), sizeof(buf)); \
/* Fill variable with 0xFF. */ \
if (fill) { \
fill_start = &var; \
fill_size = sizeof(var); \
(note "target_start" and "fill_start" being assigned the location of
(in theory) the same stack location)
This gets checked later:
/* Validate that compiler lined up fill and target. */ \
if (!range_contains(fill_start, fill_size, \
target_start, target_size)) { \
pr_err(#name ": stack fill missed target!?\n"); \
pr_err(#name ": fill %zu wide\n", fill_size); \
pr_err(#name ": target offset by %d\n", \
(int)((ssize_t)(uintptr_t)fill_start - \
(ssize_t)(uintptr_t)target_start)); \
return 1; \
which is where you're seeing the report.
> Also, I see comments making assumptions that are not true:
>
> struct test_small_hole {
> size_t one;
> char two;
> /* 3 byte padding hole here. */
> int three;
> unsigned long four;
> };
>
> On m68k (and a few other architectures), integrals of 16-bit and larger
> are aligned to a 2-byte address, so the padding may be only a single byte.
Ah! Good point. I can update the comments, but the test should still
be valid (it just has a smaller hole).
Thanks again!
--
Kees Cook
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-03-11 10:52 ` [PATCH 2/2] lib: Introduce test_stackinit module Geert Uytterhoeven
2019-04-23 22:42 ` Kees Cook
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