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kasan: fix HW_TAGS boot parameters 

The initially proposed KASAN command line parameters are redundant.

This change drops the complex "kasan.mode=off/prod/full" parameter and
adds a simpler kill switch "kasan=off/on" instead.  The new parameter
together with the already existing ones provides a cleaner way to
express the same set of features.

The full set of parameters with this change:

  kasan=off/on             - whether KASAN is enabled
  kasan.fault=report/panic - whether to only print a report or also panic
  kasan.stacktrace=off/on  - whether to collect alloc/free stack traces

Default values:

  kasan=on
  kasan.fault=report
  kasan.stacktrace=on  (if CONFIG_DEBUG_KERNEL=y)
  kasan.stacktrace=off (otherwise)

Link: https://linux-review.googlesource.com/id/Ib3694ed90b1e8ccac6cf77dfd301847af4aba7b8
Link: https://lkml.kernel.org/r/4e9c4a4bdcadc168317deb2419144582a9be6e61.1610736745.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
master
Andrey Konovalov 2021-01-23 21:01:34 -08:00 committed by Linus Torvalds
parent 5dabd1712c
commit 76bc99e81a
2 changed files with 38 additions and 66 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
Documentation/dev-tools/kasan.rst
View File

@ -160,29 +160,14 @@ 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.
The things that can be controlled are:
- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
1. Whether KASAN is enabled at all.
2. Whether KASAN collects and saves alloc/free stacks.
3. Whether KASAN panics on a detected bug or not.
- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
traces collection (default: ``on`` for ``CONFIG_DEBUG_KERNEL=y``, otherwise
``off``).
The ``kasan.mode`` boot parameter allows to choose one of three main modes:
- ``kasan.mode=off`` - KASAN is disabled, no tag checks are performed
- ``kasan.mode=prod`` - only essential production features are enabled
- ``kasan.mode=full`` - all KASAN features are enabled
The chosen mode provides default control values for the features mentioned
above. However it's also possible to override the default values by providing:
- ``kasan.stacktrace=off`` or ``=on`` - enable alloc/free stack collection
(default: ``on`` for ``mode=full``,
otherwise ``off``)
- ``kasan.fault=report`` or ``=panic`` - only print KASAN report or also panic
(default: ``report``)
If ``kasan.mode`` parameter is not provided, it defaults to ``full`` when
``CONFIG_DEBUG_KERNEL`` is enabled, and to ``prod`` otherwise.
- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN
report or also panic the kernel (default: ``report``).
For developers
~~~~~~~~~~~~~~

77
mm/kasan/hw_tags.c
View File

@ -19,11 +19,10 @@
#include "kasan.h"
enum kasan_arg_mode {
KASAN_ARG_MODE_DEFAULT,
KASAN_ARG_MODE_OFF,
KASAN_ARG_MODE_PROD,
KASAN_ARG_MODE_FULL,
enum kasan_arg {
KASAN_ARG_DEFAULT,
KASAN_ARG_OFF,
KASAN_ARG_ON,
};
enum kasan_arg_stacktrace {
@ -38,7 +37,7 @@ enum kasan_arg_fault {
KASAN_ARG_FAULT_PANIC,
};
static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
static enum kasan_arg kasan_arg __ro_after_init;
static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;
static enum kasan_arg_fault kasan_arg_fault __ro_after_init;
@ -52,26 +51,24 @@ DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
/* Whether panic or disable tag checking on fault. */
bool kasan_flag_panic __ro_after_init;
/* kasan.mode=off/prod/full */
static int __init early_kasan_mode(char *arg)
/* kasan=off/on */
static int __init early_kasan_flag(char *arg)
{
if (!arg)
return -EINVAL;
if (!strcmp(arg, "off"))
kasan_arg_mode = KASAN_ARG_MODE_OFF;
else if (!strcmp(arg, "prod"))
kasan_arg_mode = KASAN_ARG_MODE_PROD;
else if (!strcmp(arg, "full"))
kasan_arg_mode = KASAN_ARG_MODE_FULL;
kasan_arg = KASAN_ARG_OFF;
else if (!strcmp(arg, "on"))
kasan_arg = KASAN_ARG_ON;
else
return -EINVAL;
return 0;
}
early_param("kasan.mode", early_kasan_mode);
early_param("kasan", early_kasan_flag);
/* kasan.stack=off/on */
/* kasan.stacktrace=off/on */
static int __init early_kasan_flag_stacktrace(char *arg)
{
if (!arg)
@ -113,8 +110,8 @@ void kasan_init_hw_tags_cpu(void)
* as this function is only called for MTE-capable hardware.
*/
/* If KASAN is disabled, do nothing. */
if (kasan_arg_mode == KASAN_ARG_MODE_OFF)
/* If KASAN is disabled via command line, don't initialize it. */
if (kasan_arg == KASAN_ARG_OFF)
return;
hw_init_tags(KASAN_TAG_MAX);
@ -124,43 +121,28 @@ void kasan_init_hw_tags_cpu(void)
/* kasan_init_hw_tags() is called once on boot CPU. */
void __init kasan_init_hw_tags(void)
{
/* If hardware doesn't support MTE, do nothing. */
/* If hardware doesn't support MTE, don't initialize KASAN. */
if (!system_supports_mte())
return;
/* Choose KASAN mode if kasan boot parameter is not provided. */
if (kasan_arg_mode == KASAN_ARG_MODE_DEFAULT) {
if (IS_ENABLED(CONFIG_DEBUG_KERNEL))
kasan_arg_mode = KASAN_ARG_MODE_FULL;
else
kasan_arg_mode = KASAN_ARG_MODE_PROD;
}
/* Preset parameter values based on the mode. */
switch (kasan_arg_mode) {
case KASAN_ARG_MODE_DEFAULT:
/* Shouldn't happen as per the check above. */
WARN_ON(1);
/* If KASAN is disabled via command line, don't initialize it. */
if (kasan_arg == KASAN_ARG_OFF)
return;
case KASAN_ARG_MODE_OFF:
/* If KASAN is disabled, do nothing. */
return;
case KASAN_ARG_MODE_PROD:
static_branch_enable(&kasan_flag_enabled);
break;
case KASAN_ARG_MODE_FULL:
static_branch_enable(&kasan_flag_enabled);
static_branch_enable(&kasan_flag_stacktrace);
break;
}
/* Now, optionally override the presets. */
/* Enable KASAN. */
static_branch_enable(&kasan_flag_enabled);
switch (kasan_arg_stacktrace) {
case KASAN_ARG_STACKTRACE_DEFAULT:
/*
* Default to enabling stack trace collection for
* debug kernels.
*/
if (IS_ENABLED(CONFIG_DEBUG_KERNEL))
static_branch_enable(&kasan_flag_stacktrace);
break;
case KASAN_ARG_STACKTRACE_OFF:
static_branch_disable(&kasan_flag_stacktrace);
/* Do nothing, kasan_flag_stacktrace keeps its default value. */
break;
case KASAN_ARG_STACKTRACE_ON:
static_branch_enable(&kasan_flag_stacktrace);
@ -169,11 +151,16 @@ void __init kasan_init_hw_tags(void)
switch (kasan_arg_fault) {
case KASAN_ARG_FAULT_DEFAULT:
/*
* Default to no panic on report.
* Do nothing, kasan_flag_panic keeps its default value.
*/
break;
case KASAN_ARG_FAULT_REPORT:
kasan_flag_panic = false;
/* Do nothing, kasan_flag_panic keeps its default value. */
break;
case KASAN_ARG_FAULT_PANIC:
/* Enable panic on report. */
kasan_flag_panic = true;
break;
}