mm/slub, kunit: Add testcase for krealloc redzone and zeroing

Danilo Krummrich raised issue about krealloc+GFP_ZERO [1], and Vlastimil
suggested to add some test case which can sanity test the kmalloc-redzone
and zeroing by utilizing the kmalloc's 'orig_size' debug feature.

It covers the grow and shrink case of krealloc() re-using current kmalloc
object, and the case of re-allocating a new bigger object.

[1]. https://lore.kernel.org/lkml/20240812223707.32049-1-dakr@kernel.org/

Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
index 33564f9..f116913 100644 (file)
--- a/lib/slub_kunit.c
+++ b/lib/slub_kunit.c
@@ -192,6 +192,47 @@ static void test_leak_destroy(struct kunit *test)
        KUNIT_EXPECT_EQ(test, 2, slab_errors);
 }
 
+static void test_krealloc_redzone_zeroing(struct kunit *test)
+{
+       u8 *p;
+       int i;
+       struct kmem_cache *s = test_kmem_cache_create("TestSlub_krealloc", 64,
+                               SLAB_KMALLOC|SLAB_STORE_USER|SLAB_RED_ZONE);
+
+       p = alloc_hooks(__kmalloc_cache_noprof(s, GFP_KERNEL, 48));
+       memset(p, 0xff, 48);
+
+       kasan_disable_current();
+       OPTIMIZER_HIDE_VAR(p);
+
+       /* Test shrink */
+       p = krealloc(p, 40, GFP_KERNEL | __GFP_ZERO);
+       for (i = 40; i < 64; i++)
+               KUNIT_EXPECT_EQ(test, p[i], SLUB_RED_ACTIVE);
+
+       /* Test grow within the same 64B kmalloc object */
+       p = krealloc(p, 56, GFP_KERNEL | __GFP_ZERO);
+       for (i = 40; i < 56; i++)
+               KUNIT_EXPECT_EQ(test, p[i], 0);
+       for (i = 56; i < 64; i++)
+               KUNIT_EXPECT_EQ(test, p[i], SLUB_RED_ACTIVE);
+
+       validate_slab_cache(s);
+       KUNIT_EXPECT_EQ(test, 0, slab_errors);
+
+       memset(p, 0xff, 56);
+       /* Test grow with allocating a bigger 128B object */
+       p = krealloc(p, 112, GFP_KERNEL | __GFP_ZERO);
+       for (i = 0; i < 56; i++)
+               KUNIT_EXPECT_EQ(test, p[i], 0xff);
+       for (i = 56; i < 112; i++)
+               KUNIT_EXPECT_EQ(test, p[i], 0);
+
+       kfree(p);
+       kasan_enable_current();
+       kmem_cache_destroy(s);
+}
+
 static int test_init(struct kunit *test)
 {
        slab_errors = 0;
@@ -214,6 +255,7 @@ static struct kunit_case test_cases[] = {
        KUNIT_CASE(test_kmalloc_redzone_access),
        KUNIT_CASE(test_kfree_rcu),
        KUNIT_CASE(test_leak_destroy),
+       KUNIT_CASE(test_krealloc_redzone_zeroing),
        {}
 };