[PATCH v2 1/3] rcu/kasan: record and print call_rcu() call stack

Walter Wu
2020-05-11T02:31:38Z

This feature will record first and last call_rcu() call stack and
print two call_rcu() call stack in KASAN report.

When call_rcu() is called, we store the call_rcu() call stack into
slub alloc meta-data, so that KASAN report can print rcu stack.

It doesn't increase the cost of memory consumption. Because we don't
enlarge struct kasan_alloc_meta size.
- add two call_rcu() call stack into kasan_alloc_meta, size is 8 bytes.
- remove free track from kasan_alloc_meta, size is 8 bytes.

[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
[2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ

Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
---
include/linux/kasan.h | 2 ++
kernel/rcu/tree.c | 3 +++
lib/Kconfig.kasan | 2 ++
mm/kasan/common.c | 4 ++--
mm/kasan/generic.c | 29 +++++++++++++++++++++++++++++
mm/kasan/kasan.h | 19 +++++++++++++++++++
mm/kasan/report.c | 21 +++++++++++++++++----
7 files changed, 74 insertions(+), 6 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 31314ca7c635..23b7ee00572d 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -174,11 +174,13 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }

void kasan_cache_shrink(struct kmem_cache *cache);
void kasan_cache_shutdown(struct kmem_cache *cache);
+void kasan_record_aux_stack(void *ptr);

#else /* CONFIG_KASAN_GENERIC */

static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
+static inline void kasan_record_aux_stack(void *ptr) {}

#endif /* CONFIG_KASAN_GENERIC */

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 06548e2ebb72..de872b6cc261 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -57,6 +57,7 @@
#include <linux/slab.h>
#include <linux/sched/isolation.h>
#include <linux/sched/clock.h>
+#include <linux/kasan.h>
#include "../time/tick-internal.h"

#include "tree.h"
@@ -2694,6 +2695,8 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
trace_rcu_callback(rcu_state.name, head,
rcu_segcblist_n_cbs(&rdp->cblist));

+ kasan_record_aux_stack(head);
+
/* Go handle any RCU core processing required. */
if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) {
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 81f5464ea9e1..56a89291f1cc 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -58,6 +58,8 @@ config KASAN_GENERIC
For better error detection enable CONFIG_STACKTRACE.
Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
(the resulting kernel does not boot).
+ Currently CONFIG_KASAN_GENERIC will print first and last call_rcu()
+ call stack. It doesn't increase the cost of memory consumption.

config KASAN_SW_TAGS
bool "Software tag-based mode"
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 2906358e42f0..8bc618289bb1 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -41,7 +41,7 @@
#include "kasan.h"
#include "../slab.h"

-static inline depot_stack_handle_t save_stack(gfp_t flags)
+depot_stack_handle_t kasan_save_stack(gfp_t flags)
{
unsigned long entries[KASAN_STACK_DEPTH];
unsigned int nr_entries;
@@ -54,7 +54,7 @@ static inline depot_stack_handle_t save_stack(gfp_t flags)
static inline void set_track(struct kasan_track *track, gfp_t flags)
{
track->pid = current->pid;
- track->stack = save_stack(flags);
+ track->stack = kasan_save_stack(flags);
}

void kasan_enable_current(void)
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 56ff8885fe2e..b86880c338e2 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -325,3 +325,32 @@ DEFINE_ASAN_SET_SHADOW(f2);
DEFINE_ASAN_SET_SHADOW(f3);
DEFINE_ASAN_SET_SHADOW(f5);
DEFINE_ASAN_SET_SHADOW(f8);
+
+void kasan_record_aux_stack(void *addr)
+{
+ struct page *page = kasan_addr_to_page(addr);
+ struct kmem_cache *cache;
+ struct kasan_alloc_meta *alloc_info;
+ void *object;
+
+ if (!(page && PageSlab(page)))
+ return;
+
+ cache = page->slab_cache;
+ object = nearest_obj(cache, page, addr);
+ alloc_info = get_alloc_info(cache, object);
+
+ if (!alloc_info->rcu_stack[0])
+ /* record first call_rcu() call stack */
+ alloc_info->rcu_stack[0] = kasan_save_stack(GFP_NOWAIT);
+ else
+ /* record last call_rcu() call stack */
+ alloc_info->rcu_stack[1] = kasan_save_stack(GFP_NOWAIT);
+}
+
+struct kasan_track *kasan_get_aux_stack(struct kasan_alloc_meta *alloc_info,
+ u8 idx)
+{
+ return container_of(&alloc_info->rcu_stack[idx],
+ struct kasan_track, stack);
+}
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index e8f37199d885..1cc1fb7b0de3 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -96,15 +96,28 @@ struct kasan_track {
depot_stack_handle_t stack;
};

+#ifdef CONFIG_KASAN_GENERIC
+#define SIZEOF_PTR sizeof(void *)
+#define KASAN_NR_RCU_CALL_STACKS 2
+#else /* CONFIG_KASAN_GENERIC */
#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
#define KASAN_NR_FREE_STACKS 5
#else
#define KASAN_NR_FREE_STACKS 1
#endif
+#endif /* CONFIG_KASAN_GENERIC */

struct kasan_alloc_meta {
struct kasan_track alloc_track;
+#ifdef CONFIG_KASAN_GENERIC
+ /*
+ * call_rcu() call stack is stored into struct kasan_alloc_meta.
+ * The free stack is stored into freed object.
+ */
+ depot_stack_handle_t rcu_stack[KASAN_NR_RCU_CALL_STACKS];
+#else
struct kasan_track free_track[KASAN_NR_FREE_STACKS];
+#endif
#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
u8 free_pointer_tag[KASAN_NR_FREE_STACKS];
u8 free_track_idx;
@@ -159,16 +172,22 @@ void kasan_report_invalid_free(void *object, unsigned long ip);

struct page *kasan_addr_to_page(const void *addr);

+depot_stack_handle_t kasan_save_stack(gfp_t flags);
+
#if defined(CONFIG_KASAN_GENERIC) && \
(defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
void quarantine_reduce(void);
void quarantine_remove_cache(struct kmem_cache *cache);
+struct kasan_track *kasan_get_aux_stack(struct kasan_alloc_meta *alloc_info,
+ u8 idx);
#else
static inline void quarantine_put(struct kasan_free_meta *info,
struct kmem_cache *cache) { }
static inline void quarantine_reduce(void) { }
static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
+static inline struct kasan_track *kasan_get_aux_stack(
+ struct kasan_alloc_meta *alloc_info, u8 idx) { return NULL; }
#endif

#ifdef CONFIG_KASAN_SW_TAGS
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 80f23c9da6b0..f16a1a210815 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -105,9 +105,13 @@ static void end_report(unsigned long *flags)
kasan_enable_current();
}

-static void print_track(struct kasan_track *track, const char *prefix)
+static void print_track(struct kasan_track *track, const char *prefix,
+ bool is_callrcu)
{
- pr_err("%s by task %u:\n", prefix, track->pid);
+ if (is_callrcu)
+ pr_err("%s:\n", prefix);
+ else
+ pr_err("%s by task %u:\n", prefix, track->pid);
if (track->stack) {
unsigned long *entries;
unsigned int nr_entries;
@@ -187,11 +191,20 @@ static void describe_object(struct kmem_cache *cache, void *object,
if (cache->flags & SLAB_KASAN) {
struct kasan_track *free_track;

- print_track(&alloc_info->alloc_track, "Allocated");
+ print_track(&alloc_info->alloc_track, "Allocated", false);
pr_err("\n");
free_track = kasan_get_free_track(cache, object, tag);
- print_track(free_track, "Freed");
+ print_track(free_track, "Freed", false);
pr_err("\n");
+
+ if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
+ free_track = kasan_get_aux_stack(alloc_info, 0);
+ print_track(free_track, "First call_rcu() call stack", true);
+ pr_err("\n");
+ free_track = kasan_get_aux_stack(alloc_info, 1);
+ print_track(free_track, "Last call_rcu() call stack", true);
+ pr_err("\n");
+ }
}

describe_object_addr(cache, object, addr);
--
2.18.0