+ kasan-better-identify-bug-types-for-tag-based-modes.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kasan: better identify bug types for tag-based modes
has been added to the -mm mm-unstable branch.  Its filename is
     kasan-better-identify-bug-types-for-tag-based-modes.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-better-identify-bug-types-for-tag-based-modes.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Andrey Konovalov <andreyknvl@google.com>
Subject: kasan: better identify bug types for tag-based modes
Date: Mon, 5 Sep 2022 23:05:48 +0200

Identify the bug type for the tag-based modes based on the stack trace
entries found in the stack ring.

If a free entry is found first (meaning that it was added last), mark the
bug as use-after-free.  If an alloc entry is found first, mark the bug as
slab-out-of-bounds.  Otherwise, assign the common bug type.

This change returns the functionalify of the previously dropped
CONFIG_KASAN_TAGS_IDENTIFY.

Link: https://lkml.kernel.org/r/13ce7fa07d9d995caedd1439dfae4d51401842f2.1662411800.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kasan/report_tags.c |   25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

--- a/mm/kasan/report_tags.c~kasan-better-identify-bug-types-for-tag-based-modes
+++ a/mm/kasan/report_tags.c
@@ -10,7 +10,7 @@
 
 extern struct kasan_stack_ring stack_ring;
 
-static const char *get_bug_type(struct kasan_report_info *info)
+static const char *get_common_bug_type(struct kasan_report_info *info)
 {
 	/*
 	 * If access_size is a negative number, then it has reason to be
@@ -37,9 +37,8 @@ void kasan_complete_mode_report_info(str
 	bool is_free;
 	bool alloc_found = false, free_found = false;
 
-	info->bug_type = get_bug_type(info);
-
-	if (!info->cache || !info->object)
+	if (!info->cache || !info->object) {
+		info->bug_type = get_common_bug_type(info);
 		return;
 	}
 
@@ -84,6 +83,13 @@ void kasan_complete_mode_report_info(str
 			info->free_track.pid = pid;
 			info->free_track.stack = stack;
 			free_found = true;
+
+			/*
+			 * If a free entry is found first, the bug is likely
+			 * a use-after-free.
+			 */
+			if (!info->bug_type)
+				info->bug_type = "use-after-free";
 		} else {
 			/* Second alloc of the same object. Give up. */
 			if (alloc_found)
@@ -92,8 +98,19 @@ void kasan_complete_mode_report_info(str
 			info->alloc_track.pid = pid;
 			info->alloc_track.stack = stack;
 			alloc_found = true;
+
+			/*
+			 * If an alloc entry is found first, the bug is likely
+			 * an out-of-bounds.
+			 */
+			if (!info->bug_type)
+				info->bug_type = "slab-out-of-bounds";
 		}
 	}
 
 	write_unlock_irqrestore(&stack_ring.lock, flags);
+
+	/* Assign the common bug type if no entries were found. */
+	if (!info->bug_type)
+		info->bug_type = get_common_bug_type(info);
 }
_

Patches currently in -mm which might be from andreyknvl@google.com are

kasan-check-kasan_no_free_meta-in-__kasan_metadata_size.patch
kasan-rename-kasan_set__info-to-kasan_save__info.patch
kasan-move-is_kmalloc-check-out-of-save_alloc_info.patch
kasan-split-save_alloc_info-implementations.patch
kasan-drop-config_kasan_tags_identify.patch
kasan-introduce-kasan_print_aux_stacks.patch
kasan-introduce-kasan_get_alloc_track.patch
kasan-introduce-kasan_init_object_meta.patch
kasan-clear-metadata-functions-for-tag-based-modes.patch
kasan-move-kasan_get__meta-to-genericc.patch
kasan-introduce-kasan_requires_meta.patch
kasan-introduce-kasan_init_cache_meta.patch
kasan-drop-config_kasan_generic-check-from-kasan_init_cache_meta.patch
kasan-only-define-kasan_metadata_size-for-generic-mode.patch
kasan-only-define-kasan_never_merge-for-generic-mode.patch
kasan-only-define-metadata-offsets-for-generic-mode.patch
kasan-only-define-metadata-structs-for-generic-mode.patch
kasan-only-define-kasan_cache_create-for-generic-mode.patch
kasan-pass-tagged-pointers-to-kasan_save_alloc-free_info.patch
kasan-move-kasan_get_alloc-free_track-definitions.patch
kasan-cosmetic-changes-in-reportc.patch
kasan-use-virt_addr_valid-in-kasan_addr_to_page-slab.patch
kasan-use-kasan_addr_to_slab-in-print_address_description.patch
kasan-make-kasan_addr_to_page-static.patch
kasan-simplify-print_report.patch
kasan-introduce-complete_report_info.patch
kasan-fill-in-cache-and-object-in-complete_report_info.patch
kasan-rework-function-arguments-in-reportc.patch
kasan-introduce-kasan_complete_mode_report_info.patch
kasan-implement-stack-ring-for-tag-based-modes.patch
kasan-support-kasanstacktrace-for-sw_tags.patch
kasan-dynamically-allocate-stack-ring-entries.patch
kasan-better-identify-bug-types-for-tag-based-modes.patch
kasan-add-another-use-after-free-test.patch
kasan-move-tests-to-mm-kasan.patch