selftests: add a kselftest for SLUB debugging functionalityNotice: this object is not reachable from any branch.

SLUB has resiliency_test() function which is hidden behind #ifdef
SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody runs it.
Kselftest should 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_TEST_SLUB in Kconfig.

Add parameter to function validate_slab_cache() to return number of errors
in cache.

Link: https://lkml.kernel.org/r/20210316124118.6874-1-glittao@gmail.com
Signed-off-by: Oliver Glitta <glittao@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Notice: this object is not reachable from any branch.

8 files changed, 159 insertions, 12 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2779c29d9981f..2d56092abbc4a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2123,6 +2123,10 @@ config TEST_KSTRTOX
 config TEST_PRINTF
 	tristate "Test printf() family of functions at runtime"
 
+config TEST_SLUB
+	tristate "Test SLUB cache errors at runtime"
+	depends on SLUB_DEBUG
+
 config TEST_BITMAP
 	tristate "Test bitmap_*() family of functions at runtime"
 	help
diff --git a/lib/Makefile b/lib/Makefile
index b5307d3eec1aa..b6603803b1c4c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -83,6 +83,7 @@ obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
 obj-$(CONFIG_TEST_PRINTF) += test_printf.o
+obj-$(CONFIG_TEST_SLUB) += test_slub.o
 obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
 obj-$(CONFIG_TEST_STRSCPY) += test_strscpy.o
 obj-$(CONFIG_TEST_UUID) += test_uuid.o
diff --git a/lib/test_slub.c b/lib/test_slub.c
new file mode 100644
index 0000000000000..0075d9b44251f
--- /dev/null
+++ b/lib/test_slub.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test cases for slub facility.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include "../mm/slab.h"
+
+#include "../tools/testing/selftests/kselftest_module.h"
+
+
+KSTM_MODULE_GLOBALS();
+
+
+static void __init validate_result(struct kmem_cache *s, int expected_errors)
+{
+	int errors = 0;
+
+	validate_slab_cache(s, &errors);
+	KSTM_CHECK_ZERO(errors - expected_errors);
+}
+
+static void __init test_clobber_zone(void)
+{
+	struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_alloc", 64, 0,
+				SLAB_RED_ZONE, NULL);
+	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
+
+	p[64] = 0x12;
+	pr_err("1. kmem_cache: Clobber Redzone 0x12->0x%p\n", p + 64);
+
+	validate_result(s, 1);
+	kmem_cache_free(s, p);
+	kmem_cache_destroy(s);
+}
+
+static void __init test_next_pointer(void)
+{
+	struct kmem_cache *s = kmem_cache_create("TestSlub_next_ptr_free", 64, 0,
+				SLAB_RED_ZONE, NULL);
+	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
+
+	kmem_cache_free(s, p);
+	p[s->offset] = 0x12;
+	pr_err("1. kmem_cache: Clobber next pointer 0x34 -> -0x%p\n", p);
+
+	validate_result(s, 1);
+	kmem_cache_destroy(s);
+}
+
+static void __init test_first_word(void)
+{
+	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;
+	pr_err("2. kmem_cache: Clobber first word 0x78->0x%p\n", p);
+
+	validate_result(s, 1);
+	kmem_cache_destroy(s);
+}
+
+static void __init test_clobber_50th_byte(void)
+{
+	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;
+	pr_err("3. kmem_cache: Clobber 50th byte 0x9a->0x%p\n", p);
+
+	validate_result(s, 1);
+	kmem_cache_destroy(s);
+}
+
+static void __init test_clobber_redzone_free(void)
+{
+	struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_free", 64, 0,
+				SLAB_RED_ZONE, NULL);
+	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
+
+	kmem_cache_free(s, p);
+	p[64] = 0xab;
+	pr_err("4. kmem_cache: Clobber redzone 0xab->0x%p\n", p);
+
+	validate_result(s, 1);
+	kmem_cache_destroy(s);
+}
+
+static void __init resiliency_test(void)
+{
+
+	BUILD_BUG_ON(KMALLOC_MIN_SIZE > 16 || KMALLOC_SHIFT_HIGH < 10);
+
+	pr_err("SLUB resiliency testing\n");
+	pr_err("-----------------------\n");
+	pr_err("A. Corruption after allocation\n");
+
+	test_clobber_zone();
+
+	pr_err("\nB. Corruption after free\n");
+
+	test_next_pointer();
+	test_first_word();
+	test_clobber_50th_byte();
+	test_clobber_redzone_free();
+}
+
+
+static void __init selftest(void)
+{
+	resiliency_test();
+}
+
+
+KSTM_MODULE_LOADERS(test_slub);
+MODULE_LICENSE("GPL");
diff --git a/mm/slab.h b/mm/slab.h
index 73c0f21a00e21..87d80cd66f563 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -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, int *errors);
 #else
 static inline void print_tracking(struct kmem_cache *s, void *object)
 {
diff --git a/mm/slub.c b/mm/slub.c
index 34926f356e999..c6f7999f3c05c 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4629,7 +4629,8 @@ static int count_total(struct page *page)
 #endif
 
 #ifdef CONFIG_SLUB_DEBUG
-static void validate_slab(struct kmem_cache *s, struct page *page)
+static void validate_slab(struct kmem_cache *s, struct page *page,
+						int *errors)
 {
 	void *p;
 	void *addr = page_address(page);
@@ -4637,8 +4638,10 @@ static void validate_slab(struct kmem_cache *s, struct page *page)
 
 	slab_lock(page);
 
-	if (!check_slab(s, page) || !on_freelist(s, page, NULL))
+	if (!check_slab(s, page) || !on_freelist(s, page, NULL)) {
+		*errors += 1;
 		goto unlock;
+	}
 
 	/* Now we know that a valid freelist exists */
 	map = get_map(s, page);
@@ -4646,8 +4649,10 @@ static void validate_slab(struct kmem_cache *s, struct page *page)
 		u8 val = test_bit(__obj_to_index(s, addr, p), map) ?
 			 SLUB_RED_INACTIVE : SLUB_RED_ACTIVE;
 
-		if (!check_object(s, page, p, val))
+		if (!check_object(s, page, p, val)) {
+			*errors += 1;
 			break;
+		}
 	}
 	put_map(map);
 unlock:
@@ -4655,7 +4660,7 @@ unlock:
 }
 
 static int validate_slab_node(struct kmem_cache *s,
-		struct kmem_cache_node *n)
+		struct kmem_cache_node *n, int *errors)
 {
 	unsigned long count = 0;
 	struct page *page;
@@ -4664,30 +4669,34 @@ static int validate_slab_node(struct kmem_cache *s,
 	spin_lock_irqsave(&n->list_lock, flags);
 
 	list_for_each_entry(page, &n->partial, slab_list) {
-		validate_slab(s, page);
+		validate_slab(s, page, errors);
 		count++;
 	}
-	if (count != n->nr_partial)
+	if (count != n->nr_partial) {
 		pr_err("SLUB %s: %ld partial slabs counted but counter=%ld\n",
 		       s->name, count, n->nr_partial);
+		*errors += 1;
+	}
 
 	if (!(s->flags & SLAB_STORE_USER))
 		goto out;
 
 	list_for_each_entry(page, &n->full, slab_list) {
-		validate_slab(s, page);
+		validate_slab(s, page, errors);
 		count++;
 	}
-	if (count != atomic_long_read(&n->nr_slabs))
+	if (count != atomic_long_read(&n->nr_slabs)) {
 		pr_err("SLUB: %s %ld slabs counted but counter=%ld\n",
 		       s->name, count, atomic_long_read(&n->nr_slabs));
+		*errors += 1;
+	}
 
 out:
 	spin_unlock_irqrestore(&n->list_lock, flags);
 	return count;
 }
 
-static long validate_slab_cache(struct kmem_cache *s)
+long validate_slab_cache(struct kmem_cache *s, int *errors)
 {
 	int node;
 	unsigned long count = 0;
@@ -4695,10 +4704,12 @@ static long validate_slab_cache(struct kmem_cache *s)
 
 	flush_all(s);
 	for_each_kmem_cache_node(s, node, n)
-		count += validate_slab_node(s, n);
+		count += validate_slab_node(s, n, errors);
 
 	return count;
 }
+EXPORT_SYMBOL(validate_slab_cache);
+
 /*
  * Generate lists of code addresses where slabcache objects are allocated
  * and freed.
@@ -5353,9 +5364,10 @@ static ssize_t validate_store(struct kmem_cache *s,
 			const char *buf, size_t length)
 {
 	int ret = -EINVAL;
+	int errors = 0;
 
 	if (buf[0] == '1') {
-		ret = validate_slab_cache(s);
+		ret = validate_slab_cache(s, &errors);
 		if (ret >= 0)
 			ret = length;
 	}
diff --git a/tools/testing/selftests/lib/Makefile b/tools/testing/selftests/lib/Makefile
index a105f094676e1..f168313b79491 100644
--- a/tools/testing/selftests/lib/Makefile
+++ b/tools/testing/selftests/lib/Makefile
@@ -4,6 +4,6 @@
 # No binaries, but make sure arg-less "make" doesn't trigger "run_tests"
 all:
 
-TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh strscpy.sh
+TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh strscpy.sh slub.sh
 
 include ../lib.mk
diff --git a/tools/testing/selftests/lib/config b/tools/testing/selftests/lib/config
index b80ee3f6e265b..4190863032e7a 100644
--- a/tools/testing/selftests/lib/config
+++ b/tools/testing/selftests/lib/config
@@ -3,3 +3,4 @@ CONFIG_TEST_BITMAP=m
 CONFIG_PRIME_NUMBERS=m
 CONFIG_TEST_STRSCPY=m
 CONFIG_TEST_BITOPS=m
+CONFIG_TEST_SLUB=m
\ No newline at end of file
diff --git a/tools/testing/selftests/lib/slub.sh b/tools/testing/selftests/lib/slub.sh
new file mode 100644
index 0000000000000..8b57577029109
--- /dev/null
+++ b/tools/testing/selftests/lib/slub.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+$(dirname $0)/../kselftest/module.sh "slub" test_slub