Re: [PATCH v3 2/3] kasan: integrate the common part of two KASAN tag-based modes
From: Andrey Konovalov <andreyknvl@gmail.com>
Date: 2021-06-22 13:54:59
Also in:
linux-arm-kernel, linux-mm, lkml
On Sun, Jun 20, 2021 at 2:48 PM Kuan-Ying Lee [off-list ref] wrote:
1. Move kasan_get_free_track() and kasan_set_free_info() into tags.c
Please mention that the patch doesn't only move but also combines these functions for SW_TAGS and HW_TAGS modes.
quoted hunk ↗ jump to hunk
--- /dev/null +++ b/mm/kasan/report_tags.h@@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (c) 2014 Samsung Electronics Co., Ltd. + * Copyright (c) 2020 Google, Inc. + */ +#ifndef __MM_KASAN_REPORT_TAGS_H +#define __MM_KASAN_REPORT_TAGS_H + +#include "kasan.h" +#include "../slab.h" + +const char *kasan_get_bug_type(struct kasan_access_info *info)
As mentioned by Alex, don't put this implementation into a header. Put it into report_tags.c. The declaration is already in kasan.h.
+{
+#ifdef CONFIG_KASAN_TAGS_IDENTIFY
+ struct kasan_alloc_meta *alloc_meta;
+ struct kmem_cache *cache;
+ struct page *page;
+ const void *addr;
+ void *object;
+ u8 tag;
+ int i;
+
+ tag = get_tag(info->access_addr);
+ addr = kasan_reset_tag(info->access_addr);
+ page = kasan_addr_to_page(addr);
+ if (page && PageSlab(page)) {
+ cache = page->slab_cache;
+ object = nearest_obj(cache, page, (void *)addr);
+ alloc_meta = kasan_get_alloc_meta(cache, object);
+
+ if (alloc_meta) {
+ for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
+ if (alloc_meta->free_pointer_tag[i] == tag)
+ return "use-after-free";
+ }
+ }
+ return "out-of-bounds";
+ }
+#endif
+
+ /*
+ * If access_size is a negative number, then it has reason to be
+ * defined as out-of-bounds bug type.
+ *
+ * Casting negative numbers to size_t would indeed turn up as
+ * a large size_t and its value will be larger than ULONG_MAX/2,
+ * so that this can qualify as out-of-bounds.
+ */
+ if (info->access_addr + info->access_size < info->access_addr)
+ return "out-of-bounds";
+
+ return "invalid-access";
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