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: Oliver Glitta <glittao@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Daniel Latypov <dlatypov@google.com>
Acked-by: Marco 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 43 insertions, 3 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 61bd40e3eb9a..290444ab932b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -36,6 +36,7 @@
 #include <linux/prefetch.h>
 #include <linux/memcontrol.h>
 #include <linux/random.h>
+#include <kunit/test.h>
 
 #include <trace/events/kmem.h>
 
@@ -449,6 +450,26 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
 static unsigned long object_map[BITS_TO_LONGS(MAX_OBJS_PER_PAGE)];
 static DEFINE_SPINLOCK(object_map_lock);
 
+#if IS_ENABLED(CONFIG_KUNIT)
+static bool slab_add_kunit_errors(void)
+{
+	struct kunit_resource *resource;
+
+	if (likely(!current->kunit_test))
+		return false;
+
+	resource = kunit_find_named_resource(current->kunit_test, "slab_errors");
+	if (!resource)
+		return false;
+
+	(*(int *)resource->data)++;
+	kunit_put_resource(resource);
+	return true;
+}
+#else
+static inline bool slab_add_kunit_errors(void) { return false; }
+#endif
+
 /*
  * Determine a map of object in use on a page.
  *
@@ -679,6 +700,9 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...)
 	struct va_format vaf;
 	va_list args;
 
+	if (slab_add_kunit_errors())
+		return;
+
 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
@@ -742,6 +766,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
 void object_err(struct kmem_cache *s, struct page *page,
 			u8 *object, char *reason)
 {
+	if (slab_add_kunit_errors())
+		return;
+
 	slab_bug(s, "%s", reason);
 	print_trailer(s, page, object);
 }
@@ -752,6 +779,9 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
 	va_list args;
 	char buf[100];
 
+	if (slab_add_kunit_errors())
+		return;
+
 	va_start(args, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);
@@ -801,12 +831,16 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
 	while (end > fault && end[-1] == value)
 		end--;
 
+	if (slab_add_kunit_errors())
+		goto skip_bug_print;
+
 	slab_bug(s, "%s overwritten", what);
 	pr_err("0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n",
 					fault, end - 1, fault - addr,
 					fault[0], value);
 	print_trailer(s, page, object);
 
+skip_bug_print:
 	restore_bytes(s, what, value, fault, end);
 	return 0;
 }
@@ -4649,9 +4683,11 @@ static int validate_slab_node(struct kmem_cache *s,
 		validate_slab(s, page);
 		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);
+		slab_add_kunit_errors();
+	}
 
 	if (!(s->flags & SLAB_STORE_USER))
 		goto out;
@@ -4660,16 +4696,18 @@ static int validate_slab_node(struct kmem_cache *s,
 		validate_slab(s, page);
 		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));
+		slab_add_kunit_errors();
+	}
 
 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 node;
 	unsigned long count = 0;
@@ -4681,6 +4719,8 @@ static long validate_slab_cache(struct kmem_cache *s)
 
 	return count;
 }
+EXPORT_SYMBOL(validate_slab_cache);
+
 /*
  * Generate lists of code addresses where slabcache objects are allocated
  * and freed.