kasan: dynamically allocate stack ring entries
Instead of using a large static array, allocate the stack ring dynamically
via memblock_alloc().
The size of the stack ring is controlled by a new kasan.stack_ring_size
command-line parameter. When kasan.stack_ring_size is not provided, the
default value of 32 << 10 is used.
When the stack trace collection is disabled via kasan.stacktrace=off, the
stack ring is not allocated.
Link: https://lkml.kernel.org/r/03b82ab60db53427e9818e0b0c1971baa10c3cbc.1662411800.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index 7bd38c1..5c93ab9 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -112,10 +112,12 @@
if ``kasan_multi_shot`` is enabled.
Software and Hardware Tag-Based KASAN modes (see the section about various
-modes below) support disabling stack trace collection:
+modes below) support altering stack trace collection behavior:
- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
traces collection (default: ``on``).
+- ``kasan.stack_ring_size=<number of entries>`` specifies the number of entries
+ in the stack ring (default: ``32768``).
Hardware Tag-Based KASAN mode is intended for use in production as a security
mitigation. Therefore, it supports additional boot parameters that allow
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 447baf1..abbcc1b 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -252,12 +252,11 @@ struct kasan_stack_ring_entry {
bool is_free;
};
-#define KASAN_STACK_RING_SIZE (32 << 10)
-
struct kasan_stack_ring {
rwlock_t lock;
+ size_t size;
atomic64_t pos;
- struct kasan_stack_ring_entry entries[KASAN_STACK_RING_SIZE];
+ struct kasan_stack_ring_entry *entries;
};
#endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c
index 1b78136..57f73553 100644
--- a/mm/kasan/report_tags.c
+++ b/mm/kasan/report_tags.c
@@ -56,11 +56,11 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info)
* entries relevant to the buggy object can be overwritten.
*/
- for (u64 i = pos - 1; i != pos - 1 - KASAN_STACK_RING_SIZE; i--) {
+ for (u64 i = pos - 1; i != pos - 1 - stack_ring.size; i--) {
if (alloc_found && free_found)
break;
- entry = &stack_ring.entries[i % KASAN_STACK_RING_SIZE];
+ entry = &stack_ring.entries[i % stack_ring.size];
/* Paired with smp_store_release() in save_stack_info(). */
ptr = (void *)smp_load_acquire(&entry->ptr);
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index dd929ab..67a2225 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -10,6 +10,7 @@
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
+#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/static_key.h>
@@ -19,6 +20,8 @@
#include "kasan.h"
#include "../slab.h"
+#define KASAN_STACK_RING_SIZE_DEFAULT (32 << 10)
+
enum kasan_arg_stacktrace {
KASAN_ARG_STACKTRACE_DEFAULT,
KASAN_ARG_STACKTRACE_OFF,
@@ -54,6 +57,16 @@ static int __init early_kasan_flag_stacktrace(char *arg)
}
early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
+/* kasan.stack_ring_size=<number of entries> */
+static int __init early_kasan_flag_stack_ring_size(char *arg)
+{
+ if (!arg)
+ return -EINVAL;
+
+ return kstrtoul(arg, 0, &stack_ring.size);
+}
+early_param("kasan.stack_ring_size", early_kasan_flag_stack_ring_size);
+
void __init kasan_init_tags(void)
{
switch (kasan_arg_stacktrace) {
@@ -67,6 +80,16 @@ void __init kasan_init_tags(void)
static_branch_enable(&kasan_flag_stacktrace);
break;
}
+
+ if (kasan_stack_collection_enabled()) {
+ if (!stack_ring.size)
+ stack_ring.size = KASAN_STACK_RING_SIZE_DEFAULT;
+ stack_ring.entries = memblock_alloc(
+ sizeof(stack_ring.entries[0]) * stack_ring.size,
+ SMP_CACHE_BYTES);
+ if (WARN_ON(!stack_ring.entries))
+ static_branch_disable(&kasan_flag_stacktrace);
+ }
}
static void save_stack_info(struct kmem_cache *cache, void *object,
@@ -88,7 +111,7 @@ static void save_stack_info(struct kmem_cache *cache, void *object,
next:
pos = atomic64_fetch_add(1, &stack_ring.pos);
- entry = &stack_ring.entries[pos % KASAN_STACK_RING_SIZE];
+ entry = &stack_ring.entries[pos % stack_ring.size];
/* Detect stack ring entry slots that are being written to. */
old_ptr = READ_ONCE(entry->ptr);
