[PATCH v4 1/4] rcu/kasan: record and print call_rcu() call stack

Walter Wu
2020-05-19T02:24:07Z

This feature will record the last two call_rcu() call stacks and
prints up to 2 call_rcu() call stacks in KASAN report.

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

[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 | 2 ++
lib/Kconfig.kasan | 2 ++
mm/kasan/common.c | 4 ++--
mm/kasan/generic.c | 19 +++++++++++++++++++
mm/kasan/kasan.h | 10 ++++++++++
mm/kasan/report.c | 24 ++++++++++++++++++++++++
7 files changed, 61 insertions(+), 2 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..36a4ff7f320b 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"
@@ -2668,6 +2669,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
head->func = func;
head->next = NULL;
local_irq_save(flags);
+ kasan_record_aux_stack(head);
rdp = this_cpu_ptr(&rcu_data);

/* Add the callback to our list. */
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 81f5464ea9e1..4e83cf6e3caa 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).
+ In generic mode KASAN prints the last two call_rcu() call stacks in
+ reports.

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..3372bdcaf92a 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -325,3 +325,22 @@ 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);
+
+ /* record the last two call_rcu() call stacks */
+ alloc_info->aux_stack[1] = alloc_info->aux_stack[0];
+ alloc_info->aux_stack[0] = kasan_save_stack(GFP_NOWAIT);
+}
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index e8f37199d885..a7391bc83070 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -104,7 +104,15 @@ struct kasan_track {

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 struct kasan_free_meta.
+ */
+ depot_stack_handle_t aux_stack[2];
+#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;
@@ -159,6 +167,8 @@ 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);
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 80f23c9da6b0..6f8f2bf8f53b 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -179,6 +179,17 @@ static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
return &alloc_meta->free_track[i];
}

+#ifdef CONFIG_KASAN_GENERIC
+static void print_stack(depot_stack_handle_t stack)
+{
+ unsigned long *entries;
+ unsigned int nr_entries;
+
+ nr_entries = stack_depot_fetch(stack, &entries);
+ stack_trace_print(entries, nr_entries, 0);
+}
+#endif
+
static void describe_object(struct kmem_cache *cache, void *object,
const void *addr, u8 tag)
{
@@ -192,6 +203,19 @@ static void describe_object(struct kmem_cache *cache, void *object,
free_track = kasan_get_free_track(cache, object, tag);
print_track(free_track, "Freed");
pr_err("\n");
+
+#ifdef CONFIG_KASAN_GENERIC
+ if (alloc_info->aux_stack[0]) {
+ pr_err("Last one call_rcu() call stack:\n");
+ print_stack(alloc_info->aux_stack[0]);
+ pr_err("\n");
+ }
+ if (alloc_info->aux_stack[1]) {
+ pr_err("Second to last call_rcu() call stack:\n");
+ print_stack(alloc_info->aux_stack[1]);
+ pr_err("\n");
+ }
+#endif
}

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