From: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Subject: 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@xxxxxxxxxxxx: build fix] Link: http://lkml.kernel.org/r/20200710162401.23816-1-walter-zh.wu@xxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200710162123.23713-1-walter-zh.wu@xxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200601050847.1096-1-walter-zh.wu@xxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200601050927.1153-1-walter-zh.wu@xxxxxxxxxxxx Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/kasan.h | 2 ++ kernel/rcu/tree.c | 2 ++ mm/kasan/common.c | 4 ++-- mm/kasan/generic.c | 21 +++++++++++++++++++++ mm/kasan/kasan.h | 9 +++++++++ mm/kasan/report.c | 28 +++++++++++++++++++++++----- 6 files changed, 59 insertions(+), 7 deletions(-) --- a/include/linux/kasan.h~rcu-kasan-record-and-print-call_rcu-call-stack +++ a/include/linux/kasan.h @@ -174,11 +174,13 @@ static inline size_t kasan_metadata_size 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 */ --- a/kernel/rcu/tree.c~rcu-kasan-record-and-print-call_rcu-call-stack +++ a/kernel/rcu/tree.c @@ -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_ca 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. */ --- a/mm/kasan/common.c~rcu-kasan-record-and-print-call_rcu-call-stack +++ a/mm/kasan/common.c @@ -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_ 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) --- a/mm/kasan/generic.c~rcu-kasan-record-and-print-call_rcu-call-stack +++ a/mm/kasan/generic.c @@ -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); +} --- a/mm/kasan/kasan.h~rcu-kasan-record-and-print-call_rcu-call-stack +++ a/mm/kasan/kasan.h @@ -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 *obj 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); --- a/mm/kasan/report.c~rcu-kasan-record-and-print-call_rcu-call-stack +++ a/mm/kasan/report.c @@ -106,15 +106,20 @@ static void end_report(unsigned long *fl 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_ 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); _
