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-rw-r--r--mm/kasan/common.c9
-rw-r--r--mm/kasan/hw_tags.c60
-rw-r--r--mm/kasan/kasan.h27
-rw-r--r--mm/page_alloc.c43
4 files changed, 123 insertions, 16 deletions
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 833bf2cfd2a3..1d0008e1c420 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -95,19 +95,24 @@ asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
}
#endif /* CONFIG_KASAN_STACK */
-void __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
+bool __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
{
u8 tag;
unsigned long i;
if (unlikely(PageHighMem(page)))
- return;
+ return false;
+
+ if (!kasan_sample_page_alloc(order))
+ return false;
tag = kasan_random_tag();
kasan_unpoison(set_tag(page_address(page), tag),
PAGE_SIZE << order, init);
for (i = 0; i < (1 << order); i++)
page_kasan_tag_set(page + i, tag);
+
+ return true;
}
void __kasan_poison_pages(struct page *page, unsigned int order, bool init)
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index b22c4f461cb0..d1bcb0205327 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -59,6 +59,24 @@ EXPORT_SYMBOL_GPL(kasan_mode);
/* Whether to enable vmalloc tagging. */
DEFINE_STATIC_KEY_TRUE(kasan_flag_vmalloc);
+#define PAGE_ALLOC_SAMPLE_DEFAULT 1
+#define PAGE_ALLOC_SAMPLE_ORDER_DEFAULT 3
+
+/*
+ * Sampling interval of page_alloc allocation (un)poisoning.
+ * Defaults to no sampling.
+ */
+unsigned long kasan_page_alloc_sample = PAGE_ALLOC_SAMPLE_DEFAULT;
+
+/*
+ * Minimum order of page_alloc allocations to be affected by sampling.
+ * The default value is chosen to match both
+ * PAGE_ALLOC_COSTLY_ORDER and SKB_FRAG_PAGE_ORDER.
+ */
+unsigned int kasan_page_alloc_sample_order = PAGE_ALLOC_SAMPLE_ORDER_DEFAULT;
+
+DEFINE_PER_CPU(long, kasan_page_alloc_skip);
+
/* kasan=off/on */
static int __init early_kasan_flag(char *arg)
{
@@ -122,6 +140,48 @@ static inline const char *kasan_mode_info(void)
return "sync";
}
+/* kasan.page_alloc.sample=<sampling interval> */
+static int __init early_kasan_flag_page_alloc_sample(char *arg)
+{
+ int rv;
+
+ if (!arg)
+ return -EINVAL;
+
+ rv = kstrtoul(arg, 0, &kasan_page_alloc_sample);
+ if (rv)
+ return rv;
+
+ if (!kasan_page_alloc_sample || kasan_page_alloc_sample > LONG_MAX) {
+ kasan_page_alloc_sample = PAGE_ALLOC_SAMPLE_DEFAULT;
+ return -EINVAL;
+ }
+
+ return 0;
+}
+early_param("kasan.page_alloc.sample", early_kasan_flag_page_alloc_sample);
+
+/* kasan.page_alloc.sample.order=<minimum page order> */
+static int __init early_kasan_flag_page_alloc_sample_order(char *arg)
+{
+ int rv;
+
+ if (!arg)
+ return -EINVAL;
+
+ rv = kstrtouint(arg, 0, &kasan_page_alloc_sample_order);
+ if (rv)
+ return rv;
+
+ if (kasan_page_alloc_sample_order > INT_MAX) {
+ kasan_page_alloc_sample_order = PAGE_ALLOC_SAMPLE_ORDER_DEFAULT;
+ return -EINVAL;
+ }
+
+ return 0;
+}
+early_param("kasan.page_alloc.sample.order", early_kasan_flag_page_alloc_sample_order);
+
/*
* kasan_init_hw_tags_cpu() is called for each CPU.
* Not marked as __init as a CPU can be hot-plugged after boot.
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index ea8cf1310b1e..32413f22aa82 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -42,6 +42,10 @@ enum kasan_mode {
extern enum kasan_mode kasan_mode __ro_after_init;
+extern unsigned long kasan_page_alloc_sample;
+extern unsigned int kasan_page_alloc_sample_order;
+DECLARE_PER_CPU(long, kasan_page_alloc_skip);
+
static inline bool kasan_vmalloc_enabled(void)
{
return static_branch_likely(&kasan_flag_vmalloc);
@@ -57,6 +61,24 @@ static inline bool kasan_sync_fault_possible(void)
return kasan_mode == KASAN_MODE_SYNC || kasan_mode == KASAN_MODE_ASYMM;
}
+static inline bool kasan_sample_page_alloc(unsigned int order)
+{
+ /* Fast-path for when sampling is disabled. */
+ if (kasan_page_alloc_sample == 1)
+ return true;
+
+ if (order < kasan_page_alloc_sample_order)
+ return true;
+
+ if (this_cpu_dec_return(kasan_page_alloc_skip) < 0) {
+ this_cpu_write(kasan_page_alloc_skip,
+ kasan_page_alloc_sample - 1);
+ return true;
+ }
+
+ return false;
+}
+
#else /* CONFIG_KASAN_HW_TAGS */
static inline bool kasan_async_fault_possible(void)
@@ -69,6 +91,11 @@ static inline bool kasan_sync_fault_possible(void)
return true;
}
+static inline bool kasan_sample_page_alloc(unsigned int order)
+{
+ return true;
+}
+
#endif /* CONFIG_KASAN_HW_TAGS */
#ifdef CONFIG_KASAN_GENERIC
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0745aedebb37..7d980dc0000e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1356,6 +1356,8 @@ out:
* see the comment next to it.
* 3. Skipping poisoning is requested via __GFP_SKIP_KASAN_POISON,
* see the comment next to it.
+ * 4. The allocation is excluded from being checked due to sampling,
+ * see the call to kasan_unpoison_pages.
*
* Poisoning pages during deferred memory init will greatly lengthen the
* process and cause problem in large memory systems as the deferred pages
@@ -2468,7 +2470,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
{
bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags) &&
!should_skip_init(gfp_flags);
- bool init_tags = init && (gfp_flags & __GFP_ZEROTAGS);
+ bool zero_tags = init && (gfp_flags & __GFP_ZEROTAGS);
+ bool reset_tags = !zero_tags;
int i;
set_page_private(page, 0);
@@ -2491,30 +2494,42 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
*/
/*
- * If memory tags should be zeroed (which happens only when memory
- * should be initialized as well).
+ * If memory tags should be zeroed
+ * (which happens only when memory should be initialized as well).
*/
- if (init_tags) {
+ if (zero_tags) {
/* Initialize both memory and tags. */
for (i = 0; i != 1 << order; ++i)
tag_clear_highpage(page + i);
- /* Note that memory is already initialized by the loop above. */
+ /* Take note that memory was initialized by the loop above. */
init = false;
}
if (!should_skip_kasan_unpoison(gfp_flags)) {
- /* Unpoison shadow memory or set memory tags. */
- kasan_unpoison_pages(page, order, init);
-
- /* Note that memory is already initialized by KASAN. */
- if (kasan_has_integrated_init())
- init = false;
- } else {
- /* Ensure page_address() dereferencing does not fault. */
+ /* Try unpoisoning (or setting tags) and initializing memory. */
+ if (kasan_unpoison_pages(page, order, init)) {
+ /* Take note that memory was initialized by KASAN. */
+ if (kasan_has_integrated_init())
+ init = false;
+ /* Take note that memory tags were set by KASAN. */
+ reset_tags = false;
+ } else {
+ /*
+ * KASAN decided to exclude this allocation from being
+ * poisoned due to sampling. Skip poisoning as well.
+ */
+ SetPageSkipKASanPoison(page);
+ }
+ }
+ /*
+ * If memory tags have not been set, reset the page tags to ensure
+ * page_address() dereferencing does not fault.
+ */
+ if (reset_tags) {
for (i = 0; i != 1 << order; ++i)
page_kasan_tag_reset(page + i);
}
- /* If memory is still not initialized, do it now. */
+ /* If memory is still not initialized, initialize it now. */
if (init)
kernel_init_pages(page, 1 << order);
/* Propagate __GFP_SKIP_KASAN_POISON to page flags. */