Commit 26e760c9 authored by Walter Wu's avatar Walter Wu Committed by Linus Torvalds
Browse files

rcu: kasan: record and print call_rcu() call stack

Patch series "kasan: memorize and print call_rcu stack", v8.

This patchset improves KASAN reports by making them to have call_rcu()
call stack information.  It is useful for programmers to solve
use-after-free or double-free memory issue.

The KASAN report was as follows(cleaned up slightly):

BUG: KASAN: use-after-free in kasan_rcu_reclaim+0x58/0x60

Freed by task 0:
 kasan_save_stack+0x24/0x50
 kasan_set_track+0x24/0x38
 kasan_set_free_info+0x18/0x20
 __kasan_slab_free+0x10c/0x170
 kasan_slab_free+0x10/0x18
 kfree+0x98/0x270
 kasan_rcu_reclaim+0x1c/0x60

Last call_rcu():
 kasan_save_stack+0x24/0x50
 kasan_record_aux_stack+0xbc/0xd0
 call_rcu+0x8c/0x580
 kasan_rcu_uaf+0xf4/0xf8

Generic KASAN will record the last two call_rcu() call stacks and print up
to 2 call_rcu() call stacks in KASAN report.  it is only suitable for
generic KASAN.

This feature considers the size of struct kasan_alloc_meta and
kasan_free_meta, we try to optimize the structure layout and size, lets it
get better memory consumption.

[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

This patch (of 4):

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

[walter-zh.wu@mediatek.com: build fix]
  Link: http://lkml.kernel.org/r/20200710162401.23816-1-walter-zh.wu@mediatek.com

Suggested-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarWalter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Tested-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Acked-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
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>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Link: http://lkml.kernel.org/r/20200710162123.23713-1-walter-zh.wu@mediatek.com
Link: http://lkml.kernel.org/r/20200601050847.1096-1-walter-zh.wu@mediatek.com
Link: http://lkml.kernel.org/r/20200601050927.1153-1-walter-zh.wu@mediatek.com

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ac4766be
......@@ -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 */
......
......@@ -59,6 +59,7 @@
#include <linux/sched/clock.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/kasan.h>
#include "../time/tick-internal.h"
#include "tree.h"
......@@ -2890,6 +2891,7 @@ __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. */
......
......@@ -40,7 +40,7 @@
#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;
......@@ -53,7 +53,7 @@ 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)
......
......@@ -324,3 +324,24 @@ 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);
}
......@@ -104,6 +104,13 @@ 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];
#endif
struct kasan_track free_track[KASAN_NR_FREE_STACKS];
#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
u8 free_pointer_tag[KASAN_NR_FREE_STACKS];
......@@ -159,6 +166,8 @@ 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);
......
......@@ -106,15 +106,20 @@ static void end_report(unsigned long *flags)
kasan_enable_current();
}
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);
}
static void print_track(struct kasan_track *track, const char *prefix)
{
pr_err("%s by task %u:\n", prefix, track->pid);
if (track->stack) {
unsigned long *entries;
unsigned int nr_entries;
nr_entries = stack_depot_fetch(track->stack, &entries);
stack_trace_print(entries, nr_entries, 0);
print_stack(track->stack);
} else {
pr_err("(stack is not available)\n");
}
......@@ -193,6 +198,19 @@ 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 call_rcu():\n");
print_stack(alloc_info->aux_stack[0]);
pr_err("\n");
}
if (alloc_info->aux_stack[1]) {
pr_err("Second to last call_rcu():\n");
print_stack(alloc_info->aux_stack[1]);
pr_err("\n");
}
#endif
}
describe_object_addr(cache, object, addr);
......
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