On Thu, Mar 23, 2017 at 02:49:16PM +0300, Andrey Ryabinin wrote:
> + kasan_multi_shot
> + [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
> + report on every invalid memory access. Without this
> + parameter KASAN will print report only for the first
> + invalid access.
> +
The option looks fine to me.
> static int __init kmalloc_tests_init(void)
> {
> + /* Rise reports limit high enough to see all the following bugs */
> + atomic_add(100, &kasan_report_count);
> +
> + /*
> + * kasan is unreliable now, disable reports if
> + * we are in single shot mode
> + */
> + atomic_sub(100, &kasan_report_count);
> return -EAGAIN;
> }
... but these magic numbers look rather messy.
[...]
> +atomic_t kasan_report_count = ATOMIC_INIT(1);
> +EXPORT_SYMBOL_GPL(kasan_report_count);
> +
> +static int __init kasan_set_multi_shot(char *str)
> +{
> + atomic_set(&kasan_report_count, 1000000000);
> + return 1;
> +}
> +__setup("kasan_multi_shot", kasan_set_multi_shot);
... likewise.
Rather than trying to pick an arbitrarily large number, how about we use
separate flags to determine whether we're in multi-shot mode, and
whether a (oneshot) report has been made.
How about the below?
Thanks,
Mark.
---->8----
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index ceb3fe7..291d7b3 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -74,6 +74,9 @@ struct kasan_cache {
static inline void kasan_unpoison_slab(const void *ptr) { ksize(ptr); }
size_t kasan_metadata_size(struct kmem_cache *cache);
+bool kasan_save_enable_multi_shot(void);
+void kasan_restore_multi_shot(bool enabled);
+
#else /* CONFIG_KASAN */
static inline void kasan_unpoison_shadow(const void *address, size_t size) {}
diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 0b1d314..ae59dc2 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -12,6 +12,7 @@
#define pr_fmt(fmt) "kasan test: %s " fmt, __func__
#include <linux/delay.h>
+#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/mman.h>
#include <linux/mm.h>
@@ -474,6 +475,12 @@ static noinline void __init use_after_scope_test(void)
static int __init kmalloc_tests_init(void)
{
+ /*
+ * Temporarily enable multi-shot mode. Otherwise, we'd only get a
+ * report for the first case.
+ */
+ bool multishot = kasan_save_enable_multi_shot();
+
kmalloc_oob_right();
kmalloc_oob_left();
kmalloc_node_oob_right();
@@ -499,6 +506,9 @@ static int __init kmalloc_tests_init(void)
ksize_unpoisons_memory();
copy_user_test();
use_after_scope_test();
+
+ kasan_restore_multi_shot(multishot);
+
return -EAGAIN;
}
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 1c260e6..dd2dea8 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -96,11 +96,6 @@ static inline const void *kasan_shadow_to_mem(const void
*shadow_addr)
<< KASAN_SHADOW_SCALE_SHIFT);
}
-static inline bool kasan_report_enabled(void)
-{
- return !current->kasan_depth;
-}
-
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip);
void kasan_report_double_free(struct kmem_cache *cache, void *object,
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index f479365..f1c5892 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -13,6 +13,7 @@
*
*/
+#include <linux/bitops.h>
#include <linux/ftrace.h>
#include <linux/kernel.h>
#include <linux/mm.h>
@@ -293,6 +294,40 @@ static void kasan_report_error(struct kasan_access_info
*info)
kasan_end_report(&flags);
}
+static unsigned long kasan_flags;
+
+#define KASAN_BIT_REPORTED 0
+#define KASAN_BIT_MULTI_SHOT 1
+
+bool kasan_save_enable_multi_shot(void)
+{
+ return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
+}
+EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
+
+void kasan_restore_multi_shot(bool enabled)
+{
+ if (!enabled)
+ clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
+}
+EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
+
+static int __init kasan_set_multi_shot(char *str)
+{
+ set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
+ return 1;
+}
+__setup("kasan_multi_shot", kasan_set_multi_shot);
+
+static inline bool kasan_report_enabled(void)
+{
+ if (current->kasan_depth)
+ return false;
+ if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
+ return true;
+ return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
+}
+
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip)
{
