On Mon, May 11, 2020 at 4:31 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > 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@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 | 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); This is not type safe, there is no kasan_track object. And we create a pointer to kasan_track just to carefully not treat it as valid kasan_track in print_track. This adds an unnecessary if to print_track. And does not seem to be useful/nice to print: First call_rcu() call stack: (stack is not available) Last call_rcu() call stack: (stack is not available) when no rcu stacks are memorized. Your intention seems to be to reuse 2 lines of code from print_track. I would factor them out into a function: 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); } And then this can expressed as: if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { stack = alloc_info->rcu_stack[0]; if (stack) { pr_err("First call_rcu() call stack:\n"); print_stack(stack); pr_err("\n"); } stack = alloc_info->rcu_stack[1]; if (stack) { pr_err("Last call_rcu() call stack:\n"); print_stack(stack); pr_err("\n"); } } Or with another helper function it becomes: if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { print_aux_stack(alloc_info->rcu_stack[0], "First"); print_aux_stack(alloc_info->rcu_stack[1], "Last"); } > +} > 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 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20200511023111.15310-1-walter-zh.wu%40mediatek.com.
