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kasan: clarify that only first bug is reported in HW_TAGS 

Hwardware tag-based KASAN only reports the first found bug. After that MTE
tag checking gets disabled. Clarify this in comments and documentation.

Link: https://lkml.kernel.org/r/00383ba88a47c3f8342d12263c24bdf95527b07d.1612546384.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 <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2021-02-25 17:20:38 -08:00 committed by Linus Torvalds
parent c80a03664e
commit 7169487bc2
2 changed files with 7 additions and 3 deletions
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8
Documentation/dev-tools/kasan.rst
View File

@ -155,7 +155,7 @@ Boot parameters
~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~
Hardware tag-based KASAN mode (see the section about various modes 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 intended for use in production as a security mitigation. Therefore, it supports
boot parameters that allow to disable KASAN competely or otherwise control boot parameters that allow to disable KASAN competely or otherwise control
particular KASAN features. particular KASAN features.
@ -165,7 +165,8 @@ particular KASAN features.
traces collection (default: ``on``). traces collection (default: ``on``).
- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN - ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN
report or also panic the kernel (default: ``report``). report or also panic the kernel (default: ``report``). Note, that tag
checking gets disabled after the first reported bug.
For developers For developers
~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~
@ -295,6 +296,9 @@ 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 enabled. Even when kasan.mode=off is provided, or when the hardware doesn't
support MTE (but supports TBI). support MTE (but supports TBI).
Hardware tag-based KASAN only reports the first found bug. After that MTE tag
checking gets disabled.
What memory accesses are sanitised by KASAN? What memory accesses are sanitised by KASAN?
-------------------------------------------- --------------------------------------------

2
mm/kasan/hw_tags.c
View File

@ -48,7 +48,7 @@ EXPORT_SYMBOL(kasan_flag_enabled);
/* Whether to collect alloc/free stack traces. */ /* Whether to collect alloc/free stack traces. */
DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace); DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
/* Whether panic or disable tag checking on fault. */ /* Whether to panic or print a report and disable tag checking on fault. */
bool kasan_flag_panic __ro_after_init; bool kasan_flag_panic __ro_after_init;
/* kasan=off/on */ /* kasan=off/on */