Re: [PATCH RFC 2/2] lkdtm: Add heap spraying test

* Re: [PATCH RFC 2/2] lkdtm: Add heap spraying test
       [not found] ` <20200813151922.1093791-3-alex.popov@linux.com>
@ 2020-08-17 18:24   ` Eric W. Biederman
  2020-08-17 19:24     ` Kees Cook
  0 siblings, 1 reply; 2+ messages in thread
From: Eric W. Biederman @ 2020-08-17 18:24 UTC (permalink / raw)
  To: Alexander Popov
  Cc: kernel-hardening, Peter Zijlstra, David Howells, linux-mm,
	Alexander Potapenko, kasan-dev, Christoph Lameter, Will Deacon,
	Pekka Enberg, Masahiro Yamada, Krzysztof Kozlowski,
	David Rientjes, Andrey Ryabinin, Laura Abbott, Kees Cook,
	Arnd Bergmann, Jann Horn, Steven Rostedt, Joonsoo Kim,
	Dmitry Vyukov, notify, Greg Kroah-Hartman, Kexec Mailing List,
	linux-kernel, Patrick Bellasi, Masami Hiramatsu, Johannes Weiner,
	Andrew Morton

Alexander Popov <alex.popov@linux.com> writes:

> Add a simple test for CONFIG_SLAB_QUARANTINE.
>
> It performs heap spraying that aims to reallocate the recently freed heap
> object. This technique is used for exploiting use-after-free
> vulnerabilities in the kernel code.
>
> This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying
> exploitation technique.
>
> Signed-off-by: Alexander Popov <alex.popov@linux.com>

Why put this test in the linux kernel dump test module?

I have no problem with tests, and I may be wrong but this
does not look like you are testing to see if heap corruption
triggers a crash dump.  Which is what the rest of the tests
in lkdtm are about.  Seeing if the test triggers successfully
triggers a crash dump.

Eric

> ---
>  drivers/misc/lkdtm/core.c  |  1 +
>  drivers/misc/lkdtm/heap.c  | 40 ++++++++++++++++++++++++++++++++++++++
>  drivers/misc/lkdtm/lkdtm.h |  1 +
>  3 files changed, 42 insertions(+)
>
> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> index a5e344df9166..78b7669c35eb 100644
> --- a/drivers/misc/lkdtm/core.c
> +++ b/drivers/misc/lkdtm/core.c
> @@ -126,6 +126,7 @@ static const struct crashtype crashtypes[] = {
>  	CRASHTYPE(SLAB_FREE_DOUBLE),
>  	CRASHTYPE(SLAB_FREE_CROSS),
>  	CRASHTYPE(SLAB_FREE_PAGE),
> +	CRASHTYPE(HEAP_SPRAY),
>  	CRASHTYPE(SOFTLOCKUP),
>  	CRASHTYPE(HARDLOCKUP),
>  	CRASHTYPE(SPINLOCKUP),
> diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
> index 1323bc16f113..a72a241e314a 100644
> --- a/drivers/misc/lkdtm/heap.c
> +++ b/drivers/misc/lkdtm/heap.c
> @@ -205,6 +205,46 @@ static void ctor_a(void *region)
>  static void ctor_b(void *region)
>  { }
>  
> +#define HEAP_SPRAY_SIZE 128
> +
> +void lkdtm_HEAP_SPRAY(void)
> +{
> +	int *addr;
> +	int *spray_addrs[HEAP_SPRAY_SIZE] = { 0 };
> +	unsigned long i = 0;
> +
> +	addr = kmem_cache_alloc(a_cache, GFP_KERNEL);
> +	if (!addr) {
> +		pr_info("Unable to allocate memory in lkdtm-heap-a cache\n");
> +		return;
> +	}
> +
> +	*addr = 0x31337;
> +	kmem_cache_free(a_cache, addr);
> +
> +	pr_info("Performing heap spraying...\n");
> +	for (i = 0; i < HEAP_SPRAY_SIZE; i++) {
> +		spray_addrs[i] = kmem_cache_alloc(a_cache, GFP_KERNEL);
> +		*spray_addrs[i] = 0x31337;
> +		pr_info("attempt %lu: spray alloc addr %p vs freed addr %p\n",
> +						i, spray_addrs[i], addr);
> +		if (spray_addrs[i] == addr) {
> +			pr_info("freed addr is reallocated!\n");
> +			break;
> +		}
> +	}
> +
> +	if (i < HEAP_SPRAY_SIZE)
> +		pr_info("FAIL! Heap spraying succeed :(\n");
> +	else
> +		pr_info("OK! Heap spraying hasn't succeed :)\n");
> +
> +	for (i = 0; i < HEAP_SPRAY_SIZE; i++) {
> +		if (spray_addrs[i])
> +			kmem_cache_free(a_cache, spray_addrs[i]);
> +	}
> +}
> +
>  void __init lkdtm_heap_init(void)
>  {
>  	double_free_cache = kmem_cache_create("lkdtm-heap-double_free",
> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
> index 8878538b2c13..dfafb4ae6f3a 100644
> --- a/drivers/misc/lkdtm/lkdtm.h
> +++ b/drivers/misc/lkdtm/lkdtm.h
> @@ -45,6 +45,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void);
>  void lkdtm_SLAB_FREE_DOUBLE(void);
>  void lkdtm_SLAB_FREE_CROSS(void);
>  void lkdtm_SLAB_FREE_PAGE(void);
> +void lkdtm_HEAP_SPRAY(void);
>  
>  /* lkdtm_perms.c */
>  void __init lkdtm_perms_init(void);

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