On Wed, 2020-05-06 at 11:46 +0200, Dmitry Vyukov wrote: > On Wed, May 6, 2020 at 7:21 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > > > 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); > > The issue also mentions workqueue and timer stacks. > Have you considered supporting them as well? What was your motivation > for doing only rcu? > I will try to implement them when I have free time, maybe we can do it step by step, finish the printing call_rcu() first. I remember that I saw the following link, recording call_rcu seems like be needed. https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack $20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ > Looking at the first report for "workqueue use-after-free": > https://syzkaller.appspot.com/bug?extid=9cba1e478f91aad39876 > This is exactly the same situation as for call_rcu, just a workqueue > is used to invoke a callback that frees the object. > > If you don't want to do all at the same time, I would at least > name/branch everything inside of KASAN more generally (I think in the > issue I called it "aux" (auxiliary), or maybe something like > "additional"). But then call this kasan_record_aux_stack() only from > rcu for now. But then later we can separately decide and extend to > other callers. > It just feels wrong to have KASAN over-specialized for rcu only in this way. > And I think if the UAF is really caused by call_rcu callback, then it > sill will be recorded as last stack most of the time because rcu > callbacks are invoked relatively fast and there should not be much > else happening with the object since it's near end of life already. > Yes, I agree with you. I will send v2 patchset as you saying. > > > > > +#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)) > > The if is not necessary, this function is no-op when not enabled. > > > + 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 > > > > -- > > 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/20200506052046.14451-1-walter-zh.wu%40mediatek.com.
