When call_rcu() is called, we store the call_rcu() call stack into slub alloc meta-data, so that KASAN report prints call_rcu() information. We add new KASAN_RCU_STACK_RECORD configuration option. It will record first and last call_rcu() call stack and KASAN report will print two call_rcu() call stack. This option 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 Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> --- include/linux/kasan.h | 7 +++++++ kernel/rcu/tree.c | 4 ++++ lib/Kconfig.kasan | 11 +++++++++++ mm/kasan/common.c | 23 +++++++++++++++++++++++ mm/kasan/kasan.h | 12 ++++++++++++ mm/kasan/report.c | 33 +++++++++++++++++++++++++++------ 6 files changed, 84 insertions(+), 6 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 31314ca7c635..5eeece6893cd 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -96,6 +96,12 @@ size_t kasan_metadata_size(struct kmem_cache *cache); bool kasan_save_enable_multi_shot(void); void kasan_restore_multi_shot(bool enabled); +#ifdef CONFIG_KASAN_RCU_STACK_RECORD +void kasan_record_callrcu(void *ptr); +#else +static inline void kasan_record_callrcu(void *ptr) {} +#endif + #else /* CONFIG_KASAN */ static inline void kasan_unpoison_shadow(const void *address, size_t size) {} @@ -165,6 +171,7 @@ static inline void kasan_remove_zero_shadow(void *start, static inline void kasan_unpoison_slab(const void *ptr) { } static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; } +static inline void kasan_record_callrcu(void *ptr) {} #endif /* CONFIG_KASAN */ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 06548e2ebb72..145c79becf7b 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 +2695,9 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func) trace_rcu_callback(rcu_state.name, head, rcu_segcblist_n_cbs(&rdp->cblist)); + if (IS_ENABLED(CONFIG_KASAN_RCU_STACK_RECORD)) + kasan_record_callrcu(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..022934049cc2 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -158,6 +158,17 @@ config KASAN_VMALLOC for KASAN to detect more sorts of errors (and to support vmapped stacks), but at the cost of higher memory usage. +config KASAN_RCU_STACK_RECORD + bool "Record and print call_rcu() call stack" + depends on KASAN_GENERIC + help + By default, the KASAN report doesn't print call_rcu() call stack. + It is very difficult to analyze memory issues(e.g., use-after-free). + + Enabling this option will print first and last call_rcu() call stack. + It doesn't enlarge slub alloc meta-data size, so it doesn't increase + the cost of memory consumption. + config TEST_KASAN tristate "Module for testing KASAN for bug detection" depends on m && KASAN diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 2906358e42f0..32d422bdf127 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -299,6 +299,29 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache, return (void *)object + cache->kasan_info.free_meta_offset; } +#ifdef CONFIG_KASAN_RCU_STACK_RECORD +void kasan_record_callrcu(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_free_stack[0]) + /* record first call_rcu() call stack */ + alloc_info->rcu_free_stack[0] = save_stack(GFP_NOWAIT); + else + /* record last call_rcu() call stack */ + alloc_info->rcu_free_stack[1] = save_stack(GFP_NOWAIT); +} +#endif static void kasan_set_free_info(struct kmem_cache *cache, void *object, u8 tag) diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index e8f37199d885..adc105b9cd07 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -96,15 +96,27 @@ struct kasan_track { depot_stack_handle_t stack; }; +#ifdef CONFIG_KASAN_RCU_STACK_RECORD +#define BYTES_PER_WORD 4 +#define KASAN_NR_RCU_FREE_STACKS 2 +#else /* CONFIG_KASAN_RCU_STACK_RECORD */ #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY #define KASAN_NR_FREE_STACKS 5 #else #define KASAN_NR_FREE_STACKS 1 #endif +#endif /* CONFIG_KASAN_RCU_STACK_RECORD */ struct kasan_alloc_meta { struct kasan_track alloc_track; +#ifdef CONFIG_KASAN_RCU_STACK_RECORD + /* call_rcu() call stack is stored into kasan_alloc_meta. + * free stack is stored into freed object. + */ + depot_stack_handle_t rcu_free_stack[KASAN_NR_RCU_FREE_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; diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 80f23c9da6b0..7aaccc70b65b 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; @@ -159,8 +163,22 @@ static void describe_object_addr(struct kmem_cache *cache, void *object, (void *)(object_addr + cache->object_size)); } +#ifdef CONFIG_KASAN_RCU_STACK_RECORD +static void kasan_print_rcu_free_stack(struct kasan_alloc_meta *alloc_info) +{ + struct kasan_track free_track; + + free_track.stack = alloc_info->rcu_free_stack[0]; + print_track(&free_track, "First call_rcu() call stack", true); + pr_err("\n"); + free_track.stack = alloc_info->rcu_free_stack[1]; + print_track(&free_track, "Last call_rcu() call stack", true); + pr_err("\n"); +} +#endif + static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, - void *object, u8 tag) + void *object, u8 tag, const void *addr) { struct kasan_alloc_meta *alloc_meta; int i = 0; @@ -187,11 +205,14 @@ 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"); + free_track = kasan_get_free_track(cache, object, tag, addr); + print_track(free_track, "Freed", false); pr_err("\n"); +#ifdef CONFIG_KASAN_RCU_STACK_RECORD + kasan_print_rcu_free_stack(alloc_info); +#endif } describe_object_addr(cache, object, addr); -- 2.18.0
