Commit 573a4809 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

kasan: add match-all tag tests 

Add 3 new tests for tag-based KASAN modes:

1. Check that match-all pointer tag is not assigned randomly.
2. Check that 0xff works as a match-all pointer tag.
3. Check that there are no match-all memory tags.

Note, that test #3 causes a significant number (255) of KASAN reports
to be printed during execution for the SW_TAGS mode.

[arnd@arndb.de: export kasan_poison]
  Link: https://lkml.kernel.org/r/20210125112831.2156212-1-arnd@kernel.org
[akpm@linux-foundation.org: s/EXPORT_SYMBOL_GPL/EXPORT_SYMBOL/, per Andrey]

Link: https://linux-review.googlesource.com/id/I78f1375efafa162b37f3abcb2c5bc2f3955dfd8e
Link: https://lkml.kernel.org/r/da841a5408e2204bf25f3b23f70540a65844e8a4.1610733117.git.andreyknvl@google.com


Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Reviewed-by: default avatarAlexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent da17e377

lib/test_kasan.c

+92 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/mman.h>

#include <linux/module.h>

#include <linux/printk.h>

#include <linux/random.h>

#include <linux/slab.h>

#include <linux/string.h>

#include <linux/uaccess.h>
@@ -754,6 +755,94 @@ static void vmalloc_oob(struct kunit *test) 
	vfree(area);

}



/*

 * Check that the assigned pointer tag falls within the [KASAN_TAG_MIN,

 * KASAN_TAG_KERNEL) range (note: excluding the match-all tag) for tag-based

 * modes.

 */

static void match_all_not_assigned(struct kunit *test)

{

	char *ptr;

	struct page *pages;

	int i, size, order;



	KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);



	for (i = 0; i < 256; i++) {

		size = (get_random_int() % 1024) + 1;

		ptr = kmalloc(size, GFP_KERNEL);

		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

		KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);

		KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);

		kfree(ptr);

	}



	for (i = 0; i < 256; i++) {

		order = (get_random_int() % 4) + 1;

		pages = alloc_pages(GFP_KERNEL, order);

		ptr = page_address(pages);

		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

		KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);

		KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);

		free_pages((unsigned long)ptr, order);

	}

}



/* Check that 0xff works as a match-all pointer tag for tag-based modes. */

static void match_all_ptr_tag(struct kunit *test)

{

	char *ptr;

	u8 tag;



	KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);



	ptr = kmalloc(128, GFP_KERNEL);

	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);



	/* Backup the assigned tag. */

	tag = get_tag(ptr);

	KUNIT_EXPECT_NE(test, tag, (u8)KASAN_TAG_KERNEL);



	/* Reset the tag to 0xff.*/

	ptr = set_tag(ptr, KASAN_TAG_KERNEL);



	/* This access shouldn't trigger a KASAN report. */

	*ptr = 0;



	/* Recover the pointer tag and free. */

	ptr = set_tag(ptr, tag);

	kfree(ptr);

}



/* Check that there are no match-all memory tags for tag-based modes. */

static void match_all_mem_tag(struct kunit *test)

{

	char *ptr;

	int tag;



	KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);



	ptr = kmalloc(128, GFP_KERNEL);

	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

	KUNIT_EXPECT_NE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);



	/* For each possible tag value not matching the pointer tag. */

	for (tag = KASAN_TAG_MIN; tag <= KASAN_TAG_KERNEL; tag++) {

		if (tag == get_tag(ptr))

			continue;



		/* Mark the first memory granule with the chosen memory tag. */

		kasan_poison(ptr, KASAN_GRANULE_SIZE, (u8)tag);



		/* This access must cause a KASAN report. */

		KUNIT_EXPECT_KASAN_FAIL(test, *ptr = 0);

	}



	/* Recover the memory tag and free. */

	kasan_poison(ptr, KASAN_GRANULE_SIZE, get_tag(ptr));

	kfree(ptr);

}



static struct kunit_case kasan_kunit_test_cases[] = {

	KUNIT_CASE(kmalloc_oob_right),

	KUNIT_CASE(kmalloc_oob_left),
@@ -793,6 +882,9 @@ static struct kunit_case kasan_kunit_test_cases[] = { 
	KUNIT_CASE(kasan_bitops_tags),

	KUNIT_CASE(kmalloc_double_kzfree),

	KUNIT_CASE(vmalloc_oob),

	KUNIT_CASE(match_all_not_assigned),

	KUNIT_CASE(match_all_ptr_tag),

	KUNIT_CASE(match_all_mem_tag),

	{}

};

mm/kasan/kasan.h

+6 −0
Original line number Diff line number Diff line
@@ -36,6 +36,12 @@ extern bool kasan_flag_panic __ro_after_init; 
#define KASAN_TAG_INVALID	0xFE /* inaccessible memory tag */

#define KASAN_TAG_MAX		0xFD /* maximum value for random tags */



#ifdef CONFIG_KASAN_HW_TAGS

#define KASAN_TAG_MIN		0xF0 /* mimimum value for random tags */

#else

#define KASAN_TAG_MIN		0x00 /* mimimum value for random tags */

#endif



#ifdef CONFIG_KASAN_GENERIC

#define KASAN_FREE_PAGE         0xFF  /* page was freed */

#define KASAN_PAGE_REDZONE      0xFE  /* redzone for kmalloc_large allocations */

mm/kasan/shadow.c

+1 −0
Original line number Diff line number Diff line
@@ -89,6 +89,7 @@ void kasan_poison(const void *address, size_t size, u8 value) 


	__memset(shadow_start, value, shadow_end - shadow_start);

}

EXPORT_SYMBOL(kasan_poison);



void kasan_unpoison(const void *address, size_t size)

{