[PATCH RFC 8/8] kasan: add and integrate kasan_mode boot param
From: Andrey Konovalov
Date: Wed Oct 14 2020 - 16:45:25 EST
TODO: no meaningful description here yet, please see the cover letter
for this RFC series.
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Link: https://linux-review.googlesource.com/id/If7d37003875b2ed3e0935702c8015c223d6416a4
---
mm/kasan/common.c | 69 +++++++++++++++++++++++++---------------------
mm/kasan/generic.c | 4 +++
mm/kasan/hw_tags.c | 53 +++++++++++++++++++++++++++++++++++
mm/kasan/kasan.h | 8 ++++++
mm/kasan/report.c | 10 +++++--
mm/kasan/sw_tags.c | 4 +++
6 files changed, 115 insertions(+), 33 deletions(-)
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index a3e67d49b893..d642d5fce1e5 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -135,35 +135,37 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
unsigned int redzone_size;
int redzone_adjust;
- /* Add alloc meta. */
- cache->kasan_info.alloc_meta_offset = *size;
- *size += sizeof(struct kasan_alloc_meta);
-
- /* Add free meta. */
- if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
- (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
- cache->object_size < sizeof(struct kasan_free_meta))) {
- cache->kasan_info.free_meta_offset = *size;
- *size += sizeof(struct kasan_free_meta);
- }
-
- redzone_size = optimal_redzone(cache->object_size);
- redzone_adjust = redzone_size - (*size - cache->object_size);
- if (redzone_adjust > 0)
- *size += redzone_adjust;
-
- *size = min_t(unsigned int, KMALLOC_MAX_SIZE,
- max(*size, cache->object_size + redzone_size));
+ if (static_branch_unlikely(&kasan_debug)) {
+ /* Add alloc meta. */
+ cache->kasan_info.alloc_meta_offset = *size;
+ *size += sizeof(struct kasan_alloc_meta);
+
+ /* Add free meta. */
+ if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
+ (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
+ cache->object_size < sizeof(struct kasan_free_meta))) {
+ cache->kasan_info.free_meta_offset = *size;
+ *size += sizeof(struct kasan_free_meta);
+ }
- /*
- * If the metadata doesn't fit, don't enable KASAN at all.
- */
- if (*size <= cache->kasan_info.alloc_meta_offset ||
- *size <= cache->kasan_info.free_meta_offset) {
- cache->kasan_info.alloc_meta_offset = 0;
- cache->kasan_info.free_meta_offset = 0;
- *size = orig_size;
- return;
+ redzone_size = optimal_redzone(cache->object_size);
+ redzone_adjust = redzone_size - (*size - cache->object_size);
+ if (redzone_adjust > 0)
+ *size += redzone_adjust;
+
+ *size = min_t(unsigned int, KMALLOC_MAX_SIZE,
+ max(*size, cache->object_size + redzone_size));
+
+ /*
+ * If the metadata doesn't fit, don't enable KASAN at all.
+ */
+ if (*size <= cache->kasan_info.alloc_meta_offset ||
+ *size <= cache->kasan_info.free_meta_offset) {
+ cache->kasan_info.alloc_meta_offset = 0;
+ cache->kasan_info.free_meta_offset = 0;
+ *size = orig_size;
+ return;
+ }
}
*flags |= SLAB_KASAN;
@@ -180,6 +182,7 @@ size_t kasan_metadata_size(struct kmem_cache *cache)
struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
const void *object)
{
+ WARN_ON(!static_branch_unlikely(&kasan_debug));
return (void *)reset_tag(object) + cache->kasan_info.alloc_meta_offset;
}
@@ -187,6 +190,7 @@ struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
const void *object)
{
BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
+ WARN_ON(!static_branch_unlikely(&kasan_debug));
return (void *)reset_tag(object) + cache->kasan_info.free_meta_offset;
}
@@ -266,8 +270,10 @@ void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
if (!(cache->flags & SLAB_KASAN))
return (void *)object;
- alloc_meta = kasan_get_alloc_meta(cache, object);
- __memset(alloc_meta, 0, sizeof(*alloc_meta));
+ if (static_branch_unlikely(&kasan_debug)) {
+ 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));
@@ -305,6 +311,7 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
kasan_poison_memory(object, rounded_up_size, KASAN_KMALLOC_FREE);
if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
+ !static_branch_unlikely(&kasan_debug) ||
unlikely(!(cache->flags & SLAB_KASAN)))
return false;
@@ -351,7 +358,7 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
kasan_poison_memory((void *)redzone_start, redzone_end - redzone_start,
KASAN_KMALLOC_REDZONE);
- if (cache->flags & SLAB_KASAN)
+ if (static_branch_unlikely(&kasan_debug) && cache->flags & SLAB_KASAN)
set_alloc_info(cache, (void *)object, flags);
return set_tag(object, tag);
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index d259e4c3aefd..9d968eaedc98 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -33,6 +33,10 @@
#include "kasan.h"
#include "../slab.h"
+/* See the comments in hw_tags.c */
+DEFINE_STATIC_KEY_TRUE_RO(kasan_enabled);
+DEFINE_STATIC_KEY_TRUE_RO(kasan_debug);
+
/*
* All functions below always inlined so compiler could
* perform better optimizations in each of __asan_loadX/__assn_storeX
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index b372421258c8..fc6ab1c8b155 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -8,6 +8,8 @@
#define pr_fmt(fmt) "kasan: " fmt
+#include <linux/init.h>
+#include <linux/jump_label.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/memory.h>
@@ -17,8 +19,57 @@
#include "kasan.h"
+enum kasan_mode {
+ KASAN_MODE_OFF,
+ KASAN_MODE_ON,
+ KASAN_MODE_DEBUG,
+};
+
+static enum kasan_mode kasan_mode __ro_after_init;
+
+/* Whether KASAN is enabled at all. */
+/* TODO: ideally no KASAN callbacks when this is disabled. */
+DEFINE_STATIC_KEY_FALSE_RO(kasan_enabled);
+
+/* Whether to collect debugging info, e.g. alloc/free stack traces. */
+DEFINE_STATIC_KEY_FALSE_RO(kasan_debug);
+
+/* Whether to use syncronous or asynchronous tag checking. */
+static bool kasan_sync __ro_after_init;
+
+static int __init early_kasan_mode(char *arg)
+{
+ if (!arg)
+ return -EINVAL;
+
+ if (strcmp(arg, "on") == 0)
+ kasan_mode = KASAN_MODE_ON;
+ else if (strcmp(arg, "debug") == 0)
+ kasan_mode = KASAN_MODE_DEBUG;
+ return 0;
+}
+early_param("kasan_mode", early_kasan_mode);
+
void __init kasan_init_tags(void)
{
+ /* TODO: system_supports_tags() always returns 0 here, fix. */
+ if (0 /*!system_supports_tags()*/)
+ return;
+
+ switch (kasan_mode) {
+ case KASAN_MODE_OFF:
+ return;
+ case KASAN_MODE_ON:
+ static_branch_enable(&kasan_enabled);
+ break;
+ case KASAN_MODE_DEBUG:
+ static_branch_enable(&kasan_enabled);
+ static_branch_enable(&kasan_debug);
+ kasan_sync = true;
+ break;
+ }
+
+ /* TODO: choose between sync and async based on kasan_sync. */
init_tags(KASAN_TAG_MAX);
pr_info("KernelAddressSanitizer initialized\n");
@@ -60,6 +111,7 @@ void kasan_set_free_info(struct kmem_cache *cache,
{
struct kasan_alloc_meta *alloc_meta;
+ WARN_ON(!static_branch_unlikely(&kasan_debug));
alloc_meta = kasan_get_alloc_meta(cache, object);
kasan_set_track(&alloc_meta->free_track[0], GFP_NOWAIT);
}
@@ -69,6 +121,7 @@ struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
{
struct kasan_alloc_meta *alloc_meta;
+ WARN_ON(!static_branch_unlikely(&kasan_debug));
alloc_meta = kasan_get_alloc_meta(cache, object);
return &alloc_meta->free_track[0];
}
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 47d6074c7958..3712e7a39717 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -279,6 +279,14 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
#define get_mem_tag(addr) arch_get_mem_tag(addr)
#define set_mem_tag_range(addr, size, tag) arch_set_mem_tag_range((addr), (size), (tag))
+#ifdef CONFIG_KASAN_HW_TAGS
+DECLARE_STATIC_KEY_FALSE(kasan_enabled);
+DECLARE_STATIC_KEY_FALSE(kasan_debug);
+#else
+DECLARE_STATIC_KEY_TRUE(kasan_enabled);
+DECLARE_STATIC_KEY_TRUE(kasan_debug);
+#endif
+
/*
* Exported functions for interfaces called from assembly or from generated
* code. Declarations here to avoid warning about missing declarations.
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index dee5350b459c..ae956a29ad4e 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -159,8 +159,8 @@ 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);
@@ -188,7 +188,13 @@ 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 (static_branch_unlikely(&kasan_debug))
+ describe_object_stacks(cache, object, addr, tag);
describe_object_addr(cache, object, addr);
}
diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
index 099af6dc8f7e..50e797a16e17 100644
--- a/mm/kasan/sw_tags.c
+++ b/mm/kasan/sw_tags.c
@@ -33,6 +33,10 @@
#include "kasan.h"
#include "../slab.h"
+/* See the comments in hw_tags.c */
+DEFINE_STATIC_KEY_TRUE_RO(kasan_enabled);
+DEFINE_STATIC_KEY_TRUE_RO(kasan_debug);
+
static DEFINE_PER_CPU(u32, prng_state);
void __init kasan_init_tags(void)
--
2.28.0.1011.ga647a8990f-goog