From: Andrey Konovalov <andreyknvl@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Dmitry Vyukov <dvyukov@google.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Branislav Rankov <Branislav.Rankov@arm.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrey Konovalov <andreyknvl@google.com>
Subject: [PATCH mm v4 11/19] kasan: add and integrate kasan boot parameters
Date: Mon, 23 Nov 2020 21:14:41 +0100 [thread overview]
Message-ID: <cb093613879d8d8841173f090133eddeb4c35f1f.1606162397.git.andreyknvl@google.com> (raw)
In-Reply-To: <cover.1606162397.git.andreyknvl@google.com>
Hardware tag-based KASAN mode is intended to eventually be used in
production as a security mitigation. Therefore there's a need for finer
control over KASAN features and for an existence of a kill switch.
This change adds a few boot parameters for hardware tag-based KASAN that
allow to disable or otherwise control particular KASAN features.
The features that can be controlled are:
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.
With this change a new boot parameter kasan.mode 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/on - enable alloc/free stack collection
(default: on for mode=full, otherwise off)
- kasan.fault=report/panic - only report tag fault 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.
It is essential that switching between these modes doesn't require
rebuilding the kernel with different configs, as this is required by
the Android GKI (Generic Kernel Image) initiative [1].
[1] https://source.android.com/devices/architecture/kernel/generic-kernel-image
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Link: https://linux-review.googlesource.com/id/If7d37003875b2ed3e0935702c8015c223d6416a4
---
mm/kasan/common.c | 22 +++++--
mm/kasan/hw_tags.c | 151 +++++++++++++++++++++++++++++++++++++++++++++
mm/kasan/kasan.h | 16 +++++
mm/kasan/report.c | 14 ++++-
4 files changed, 196 insertions(+), 7 deletions(-)
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 1ac4f435c679..a11e3e75eb08 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -135,6 +135,11 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
unsigned int redzone_size;
int redzone_adjust;
+ if (!kasan_stack_collection_enabled()) {
+ *flags |= SLAB_KASAN;
+ return;
+ }
+
/* Add alloc meta. */
cache->kasan_info.alloc_meta_offset = *size;
*size += sizeof(struct kasan_alloc_meta);
@@ -171,6 +176,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
size_t kasan_metadata_size(struct kmem_cache *cache)
{
+ if (!kasan_stack_collection_enabled())
+ return 0;
return (cache->kasan_info.alloc_meta_offset ?
sizeof(struct kasan_alloc_meta) : 0) +
(cache->kasan_info.free_meta_offset ?
@@ -263,11 +270,13 @@ void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
{
struct kasan_alloc_meta *alloc_meta;
- if (!(cache->flags & SLAB_KASAN))
- return (void *)object;
+ if (kasan_stack_collection_enabled()) {
+ if (!(cache->flags & SLAB_KASAN))
+ return (void *)object;
- alloc_meta = kasan_get_alloc_meta(cache, object);
- __memset(alloc_meta, 0, sizeof(*alloc_meta));
+ alloc_meta = kasan_get_alloc_meta(cache, object);
+ __memset(alloc_meta, 0, sizeof(*alloc_meta));
+ }
if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) || IS_ENABLED(CONFIG_KASAN_HW_TAGS))
object = set_tag(object, assign_tag(cache, object, true, false));
@@ -307,6 +316,9 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
rounded_up_size = round_up(cache->object_size, KASAN_GRANULE_SIZE);
poison_range(object, rounded_up_size, KASAN_KMALLOC_FREE);
+ if (!kasan_stack_collection_enabled())
+ return false;
+
if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
unlikely(!(cache->flags & SLAB_KASAN)))
return false;
@@ -357,7 +369,7 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
poison_range((void *)redzone_start, redzone_end - redzone_start,
KASAN_KMALLOC_REDZONE);
- if (cache->flags & SLAB_KASAN)
+ if (kasan_stack_collection_enabled() && (cache->flags & SLAB_KASAN))
set_alloc_info(cache, (void *)object, flags);
return set_tag(object, tag);
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 863fed4edd3f..30ce88935e9d 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -8,18 +8,115 @@
#define pr_fmt(fmt) "kasan: " fmt
+#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/memory.h>
#include <linux/mm.h>
+#include <linux/static_key.h>
#include <linux/string.h>
#include <linux/types.h>
#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_stacktrace {
+ KASAN_ARG_STACKTRACE_DEFAULT,
+ KASAN_ARG_STACKTRACE_OFF,
+ KASAN_ARG_STACKTRACE_ON,
+};
+
+enum kasan_arg_fault {
+ KASAN_ARG_FAULT_DEFAULT,
+ KASAN_ARG_FAULT_REPORT,
+ KASAN_ARG_FAULT_PANIC,
+};
+
+static enum kasan_arg_mode kasan_arg_mode __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;
+
+/* Whether KASAN is enabled at all. */
+DEFINE_STATIC_KEY_FALSE_RO(kasan_flag_enabled);
+EXPORT_SYMBOL(kasan_flag_enabled);
+
+/* Whether to collect alloc/free stack traces. */
+DEFINE_STATIC_KEY_FALSE_RO(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)
+{
+ 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;
+ else
+ return -EINVAL;
+
+ return 0;
+}
+early_param("kasan.mode", early_kasan_mode);
+
+/* kasan.stack=off/on */
+static int __init early_kasan_flag_stacktrace(char *arg)
+{
+ if (!arg)
+ return -EINVAL;
+
+ if (!strcmp(arg, "off"))
+ kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
+ else if (!strcmp(arg, "on"))
+ kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
+ else
+ return -EINVAL;
+
+ return 0;
+}
+early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
+
+/* kasan.fault=report/panic */
+static int __init early_kasan_fault(char *arg)
+{
+ if (!arg)
+ return -EINVAL;
+
+ if (!strcmp(arg, "report"))
+ kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
+ else if (!strcmp(arg, "panic"))
+ kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
+ else
+ return -EINVAL;
+
+ return 0;
+}
+early_param("kasan.fault", early_kasan_fault);
+
/* kasan_init_hw_tags_cpu() is called for each CPU. */
void kasan_init_hw_tags_cpu(void)
{
+ /*
+ * There's no need to check that the hardware is MTE-capable here,
+ * as this function is only called for MTE-capable hardware.
+ */
+
+ /* If KASAN is disabled, do nothing. */
+ if (kasan_arg_mode == KASAN_ARG_MODE_OFF)
+ return;
+
hw_init_tags(KASAN_TAG_MAX);
hw_enable_tagging();
}
@@ -27,6 +124,60 @@ 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 (!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);
+ 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. */
+
+ switch (kasan_arg_stacktrace) {
+ case KASAN_ARG_STACKTRACE_DEFAULT:
+ break;
+ case KASAN_ARG_STACKTRACE_OFF:
+ static_branch_disable(&kasan_flag_stacktrace);
+ break;
+ case KASAN_ARG_STACKTRACE_ON:
+ static_branch_enable(&kasan_flag_stacktrace);
+ break;
+ }
+
+ switch (kasan_arg_fault) {
+ case KASAN_ARG_FAULT_DEFAULT:
+ break;
+ case KASAN_ARG_FAULT_REPORT:
+ kasan_flag_panic = false;
+ break;
+ case KASAN_ARG_FAULT_PANIC:
+ kasan_flag_panic = true;
+ break;
+ }
+
pr_info("KernelAddressSanitizer initialized\n");
}
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 8aa83b7ad79e..d01a5ac34f70 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -6,6 +6,22 @@
#include <linux/kfence.h>
#include <linux/stackdepot.h>
+#ifdef CONFIG_KASAN_HW_TAGS
+#include <linux/static_key.h>
+DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
+static inline bool kasan_stack_collection_enabled(void)
+{
+ return static_branch_unlikely(&kasan_flag_stacktrace);
+}
+#else
+static inline bool kasan_stack_collection_enabled(void)
+{
+ return true;
+}
+#endif
+
+extern bool kasan_flag_panic __ro_after_init;
+
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
#define KASAN_GRANULE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT)
#else
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 76a0e3ae2049..ffa6076b1710 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -99,6 +99,10 @@ static void end_report(unsigned long *flags)
panic_on_warn = 0;
panic("panic_on_warn set ...\n");
}
+#ifdef CONFIG_KASAN_HW_TAGS
+ if (kasan_flag_panic)
+ panic("kasan.fault=panic set ...\n");
+#endif
kasan_enable_current();
}
@@ -161,8 +165,8 @@ static void describe_object_addr(struct kmem_cache *cache, void *object,
(void *)(object_addr + cache->object_size));
}
-static void describe_object(struct kmem_cache *cache, void *object,
- const void *addr, u8 tag)
+static void describe_object_stacks(struct kmem_cache *cache, void *object,
+ const void *addr, u8 tag)
{
struct kasan_alloc_meta *alloc_meta = kasan_get_alloc_meta(cache, object);
@@ -190,7 +194,13 @@ static void describe_object(struct kmem_cache *cache, void *object,
}
#endif
}
+}
+static void describe_object(struct kmem_cache *cache, void *object,
+ const void *addr, u8 tag)
+{
+ if (kasan_stack_collection_enabled())
+ describe_object_stacks(cache, object, addr, tag);
describe_object_addr(cache, object, addr);
}
--
2.29.2.454.gaff20da3a2-goog
next prev parent reply other threads:[~2020-11-23 20:15 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-23 20:14 [PATCH mm v4 00/19] kasan: boot parameters for hardware tag-based mode Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 01/19] kasan: simplify quarantine_put call site Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 02/19] kasan: rename get_alloc/free_info Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 03/19] kasan: introduce set_alloc_info Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 04/19] kasan, arm64: unpoison stack only with CONFIG_KASAN_STACK Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 05/19] kasan: allow VMAP_STACK for HW_TAGS mode Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 06/19] kasan: remove __kasan_unpoison_stack Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 07/19] kasan: inline kasan_reset_tag for tag-based modes Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 08/19] kasan: inline random_tag for HW_TAGS Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 09/19] kasan: open-code kasan_unpoison_slab Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 10/19] kasan: inline (un)poison_range and check_invalid_free Andrey Konovalov
2020-11-23 20:14 ` Andrey Konovalov [this message]
2020-11-23 20:14 ` [PATCH mm v4 12/19] kasan, mm: check kasan_enabled in annotations Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 13/19] kasan, mm: rename kasan_poison_kfree Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 14/19] kasan: don't round_up too much Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 15/19] kasan: simplify assign_tag and set_tag calls Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 16/19] kasan: clarify comment in __kasan_kfree_large Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 17/19] kasan: sanitize objects when metadata doesn't fit Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 18/19] kasan, mm: allow cache merging with no metadata Andrey Konovalov
2020-11-23 20:14 ` [PATCH mm v4 19/19] kasan: update documentation Andrey Konovalov
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