Commit 1f9f78b1 authored by Oliver Glitta's avatar Oliver Glitta Committed by Linus Torvalds
Browse files

mm/slub, kunit: add a KUnit test for SLUB debugging functionality 

SLUB has resiliency_test() function which is hidden behind #ifdef
SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody runs it.
KUnit should be a proper replacement for it.

Try changing byte in redzone after allocation and changing pointer to next
free node, first byte, 50th byte and redzone byte.  Check if validation
finds errors.

There are several differences from the original resiliency test: Tests
create own caches with known state instead of corrupting shared kmalloc
caches.

The corruption of freepointer uses correct offset, the original resiliency
test got broken with freepointer changes.

Scratch changing random byte test, because it does not have meaning in
this form where we need deterministic results.

Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.  Tests next_pointer,
first_word and clobber_50th_byte do not run with KASAN option on.  Because
the test deliberately modifies non-allocated objects.

Use kunit_resource to count errors in cache and silence bug reports.
Count error whenever slab_bug() or slab_fix() is called or when the count
of pages is wrong.

[glittao@gmail.com: remove unused function test_exit(), from SLUB KUnit test]
  Link: https://lkml.kernel.org/r/20210512140656.12083-1-glittao@gmail.com
[akpm@linux-foundation.org: export kasan_enable/disable_current to modules]

Link: https://lkml.kernel.org/r/20210511150734.3492-2-glittao@gmail.com


Signed-off-by: default avatarOliver Glitta <glittao@gmail.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarDaniel Latypov <dlatypov@google.com>
Acked-by: default avatarMarco Elver <elver@google.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 26c6cb7c

lib/Kconfig.debug

+12 −0
Original line number Diff line number Diff line
@@ -2429,6 +2429,18 @@ config BITS_TEST 


	  If unsure, say N.



config SLUB_KUNIT_TEST

	tristate "KUnit test for SLUB cache error detection" if !KUNIT_ALL_TESTS

	depends on SLUB_DEBUG && KUNIT

	default KUNIT_ALL_TESTS

	help

	  This builds SLUB allocator unit test.

	  Tests SLUB cache debugging functionality.

	  For more information on KUnit and unit tests in general please refer

	  to the KUnit documentation in Documentation/dev-tools/kunit/.



	  If unsure, say N.



config TEST_UDELAY

	tristate "udelay test driver"

	help

lib/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -354,5 +354,6 @@ obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o 
obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o

obj-$(CONFIG_BITS_TEST) += test_bits.o

obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o

obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o



obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o

lib/slub_kunit.c

0 → 100644
+152 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <kunit/test.h>

#include <linux/mm.h>

#include <linux/slab.h>

#include <linux/module.h>

#include <linux/kernel.h>

#include "../mm/slab.h"



static struct kunit_resource resource;

static int slab_errors;



static void test_clobber_zone(struct kunit *test)

{

	struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_alloc", 64, 0,

				SLAB_RED_ZONE, NULL);

	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);



	kasan_disable_current();

	p[64] = 0x12;



	validate_slab_cache(s);

	KUNIT_EXPECT_EQ(test, 2, slab_errors);



	kasan_enable_current();

	kmem_cache_free(s, p);

	kmem_cache_destroy(s);

}



#ifndef CONFIG_KASAN

static void test_next_pointer(struct kunit *test)

{

	struct kmem_cache *s = kmem_cache_create("TestSlub_next_ptr_free", 64, 0,

				SLAB_POISON, NULL);

	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);

	unsigned long tmp;

	unsigned long *ptr_addr;



	kmem_cache_free(s, p);



	ptr_addr = (unsigned long *)(p + s->offset);

	tmp = *ptr_addr;

	p[s->offset] = 0x12;



	/*

	 * Expecting three errors.

	 * One for the corrupted freechain and the other one for the wrong

	 * count of objects in use. The third error is fixing broken cache.

	 */

	validate_slab_cache(s);

	KUNIT_EXPECT_EQ(test, 3, slab_errors);



	/*

	 * Try to repair corrupted freepointer.

	 * Still expecting two errors. The first for the wrong count

	 * of objects in use.

	 * The second error is for fixing broken cache.

	 */

	*ptr_addr = tmp;

	slab_errors = 0;



	validate_slab_cache(s);

	KUNIT_EXPECT_EQ(test, 2, slab_errors);



	/*

	 * Previous validation repaired the count of objects in use.

	 * Now expecting no error.

	 */

	slab_errors = 0;

	validate_slab_cache(s);

	KUNIT_EXPECT_EQ(test, 0, slab_errors);



	kmem_cache_destroy(s);

}



static void test_first_word(struct kunit *test)

{

	struct kmem_cache *s = kmem_cache_create("TestSlub_1th_word_free", 64, 0,

				SLAB_POISON, NULL);

	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);



	kmem_cache_free(s, p);

	*p = 0x78;



	validate_slab_cache(s);

	KUNIT_EXPECT_EQ(test, 2, slab_errors);



	kmem_cache_destroy(s);

}



static void test_clobber_50th_byte(struct kunit *test)

{

	struct kmem_cache *s = kmem_cache_create("TestSlub_50th_word_free", 64, 0,

				SLAB_POISON, NULL);

	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);



	kmem_cache_free(s, p);

	p[50] = 0x9a;



	validate_slab_cache(s);

	KUNIT_EXPECT_EQ(test, 2, slab_errors);



	kmem_cache_destroy(s);

}

#endif



static void test_clobber_redzone_free(struct kunit *test)

{

	struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_free", 64, 0,

				SLAB_RED_ZONE, NULL);

	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);



	kasan_disable_current();

	kmem_cache_free(s, p);

	p[64] = 0xab;



	validate_slab_cache(s);

	KUNIT_EXPECT_EQ(test, 2, slab_errors);



	kasan_enable_current();

	kmem_cache_destroy(s);

}



static int test_init(struct kunit *test)

{

	slab_errors = 0;



	kunit_add_named_resource(test, NULL, NULL, &resource,

					"slab_errors", &slab_errors);

	return 0;

}



static struct kunit_case test_cases[] = {

	KUNIT_CASE(test_clobber_zone),



#ifndef CONFIG_KASAN

	KUNIT_CASE(test_next_pointer),

	KUNIT_CASE(test_first_word),

	KUNIT_CASE(test_clobber_50th_byte),

#endif



	KUNIT_CASE(test_clobber_redzone_free),

	{}

};



static struct kunit_suite test_suite = {

	.name = "slub_test",

	.init = test_init,

	.test_cases = test_cases,

};

kunit_test_suite(test_suite);



MODULE_LICENSE("GPL");

mm/kasan/common.c

+3 −0
Original line number Diff line number Diff line
@@ -51,11 +51,14 @@ void kasan_enable_current(void) 
{

	current->kasan_depth++;

}

EXPORT_SYMBOL(kasan_enable_current);



void kasan_disable_current(void)

{

	current->kasan_depth--;

}

EXPORT_SYMBOL(kasan_disable_current);



#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */



void __kasan_unpoison_range(const void *address, size_t size)

mm/slab.h

+1 −0
Original line number Diff line number Diff line
@@ -215,6 +215,7 @@ DECLARE_STATIC_KEY_TRUE(slub_debug_enabled); 
DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);

#endif

extern void print_tracking(struct kmem_cache *s, void *object);

long validate_slab_cache(struct kmem_cache *s);

#else

static inline void print_tracking(struct kmem_cache *s, void *object)

{