The patch titled
Subject: kasan: clarify HW_TAGS impact on TBI
has been added to the -mm tree. Its filename is
kasan-clarify-hw_tags-impact-on-tbi.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kasan-clarify-hw_tags-impact-on-tbi.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kasan-clarify-hw_tags-impact-on-tbi.patch
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------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: kasan: clarify HW_TAGS impact on TBI
Mention in the documentation that enabling CONFIG_KASAN_HW_TAGS always
results in in-kernel TBI (Top Byte Ignore) being enabled.
Also do a few minor documentation cleanups.
Link: https://linux-review.googlesource.com/id/Iba2a6697e3c6304cb53f89ec61dedc77fa29e3ae
Link: https://lkml.kernel.org/r/3b4ea6875bb14d312092ad14ac55cb456c83c08e.1610733117.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Branislav Rankov <Branislav.Rankov@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx>
Cc: Kevin Brodsky <kevin.brodsky@xxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/dev-tools/kasan.rst | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
--- a/Documentation/dev-tools/kasan.rst~kasan-clarify-hw_tags-impact-on-tbi
+++ a/Documentation/dev-tools/kasan.rst
@@ -147,15 +147,14 @@ negative values to distinguish between d
like redzones or freed memory (see mm/kasan/kasan.h).
In the report above the arrows point to the shadow byte 03, which means that
-the accessed address is partially accessible.
-
-For tag-based KASAN this last report section shows the memory tags around the
-accessed address (see `Implementation details`_ section).
+the accessed address is partially accessible. For tag-based KASAN modes this
+last report section shows the memory tags around the accessed address
+(see the `Implementation details`_ section).
Boot parameters
~~~~~~~~~~~~~~~
-Hardware tag-based KASAN mode (see the section about different mode below) is
+Hardware tag-based KASAN mode (see the section about various modes below) is
intended for use in production as a security mitigation. Therefore it supports
boot parameters that allow to disable KASAN competely or otherwise control
particular KASAN features.
@@ -290,6 +289,13 @@ reserved to tag freed memory regions.
Hardware tag-based KASAN currently only supports tagging of
kmem_cache_alloc/kmalloc and page_alloc memory.
+If the hardware doesn't support MTE (pre ARMv8.5), hardware tag-based KASAN
+won't be enabled. In this case all boot parameters are ignored.
+
+Note, that enabling CONFIG_KASAN_HW_TAGS always results in in-kernel TBI being
+enabled. Even when kasan.mode=off is provided, or when the hardware doesn't
+support MTE (but supports TBI).
+
What memory accesses are sanitised by KASAN?
--------------------------------------------
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
kasan-fix-hw_tags-boot-parameters.patch
kasan-prefix-global-functions-with-kasan_.patch
kasan-clarify-hw_tags-impact-on-tbi.patch
kasan-clean-up-comments-in-tests.patch
kasan-add-macros-to-simplify-checking-test-constraints.patch
kasan-add-match-all-tag-tests.patch
kasan-arm64-allow-using-kunit-tests-with-hw_tags-mode.patch
kasan-rename-config_test_kasan_module.patch
kasan-add-compiler-barriers-to-kunit_expect_kasan_fail.patch
kasan-adapt-kmalloc_uaf2-test-to-hw_tags-mode.patch
kasan-fix-memory-corruption-in-kasan_bitops_tags-test.patch
kasan-move-_ret_ip_-to-inline-wrappers.patch
kasan-fix-bug-detection-via-ksize-for-hw_tags-mode.patch
kasan-add-proper-page-allocator-tests.patch
kasan-add-a-test-for-kmem_cache_alloc-free_bulk.patch
kasan-dont-run-tests-when-kasan-is-not-enabled.patch
