From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 559DCC54E8D for ; Tue, 12 May 2020 02:36:55 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 17F9E20769 for ; Tue, 12 May 2020 02:36:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="J+95fkKn"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b="NQkHlMbJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 17F9E20769 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=mediatek.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Date:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=oqOnB+itqKfoOelgr37+hSJ4gAcDcuibhyMLBhIjBBI=; b=J+95fkKnOz+5MO T/XdhZcosa1F1UiRFdXs/3Tbi4IYKOcqo1mRHBhvLnd5WcRD56gMYz24w39XjrOKaSw4ejU7EVSFG Z9R1GHQ27IBKEJ70FLze0WYbPmZLV1Nzt/cTRduISvApyryJrVkPWF5isvNo3ed+dJ85ZWuoyBXbk MoL3TWs4pUJ1aYx6keZrVY3boaFX71fTYqCT7PgeyRI1n5D+uLKAttgCwBXUYJTHUTXn6CsJxYuBS gutjknWs0NzCWjaQt8a5QG3zGRSrIZvOymPfB88Xrz/cwWUpMKohKbML6zChIs3r+QldL4/zx7rna 3XCQsH/bf3ycfxB95qwA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYKms-0007db-9E; Tue, 12 May 2020 02:36:54 +0000 Received: from mailgw02.mediatek.com ([216.200.240.185]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYKmm-0007bL-CG; Tue, 12 May 2020 02:36:52 +0000 X-UUID: 22591216240b4b73b84d164ba3752973-20200511 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Transfer-Encoding:MIME-Version:Content-Type:References:In-Reply-To:Date:CC:To:From:Subject:Message-ID; bh=FQ7XyHiA4cqNGdsuVZJtrzYx0SKzIOlxJaYrSNfV8VA=; b=NQkHlMbJH3AwVH6A3RS5lhC3lDU8S/HdmWed0w8+0u+iB5nyRYvt0dz4CsEiystUOMsH6bfdFq6MLpknfF4FE5MiHQW8e1fGFPqrhPlZ+D/5W7X4rDs0xGvP+e/hgRqxieohgxaGX7v3vNGem8wPQrlsFm9/hzCJ2JAKeHT0SaE=; X-UUID: 22591216240b4b73b84d164ba3752973-20200511 Received: from mtkcas66.mediatek.inc [(172.29.193.44)] by mailgw02.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLS) with ESMTP id 444389267; Mon, 11 May 2020 18:36:41 -0800 Received: from MTKMBS01N1.mediatek.inc (172.21.101.68) by MTKMBS62N2.mediatek.inc (172.29.193.42) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 11 May 2020 19:36:40 -0700 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs01n1.mediatek.inc (172.21.101.68) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 12 May 2020 10:36:29 +0800 Received: from [172.21.84.99] (172.21.84.99) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Tue, 12 May 2020 10:36:29 +0800 Message-ID: <1589250993.19238.22.camel@mtksdccf07> Subject: Re: [PATCH v2 1/3] rcu/kasan: record and print call_rcu() call stack From: Walter Wu To: Date: Tue, 12 May 2020 10:36:33 +0800 In-Reply-To: <20200511180527.GZ2869@paulmck-ThinkPad-P72> References: <20200511023111.15310-1-walter-zh.wu@mediatek.com> <20200511180527.GZ2869@paulmck-ThinkPad-P72> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200511_193648_449585_34882F2B X-CRM114-Status: GOOD ( 30.01 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: wsd_upstream , linux-mm@kvack.org, Lai Jiangshan , Josh Triplett , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, Joel Fernandes , linux-mediatek@lists.infradead.org, Alexander Potapenko , linux-arm-kernel@lists.infradead.org, Matthias Brugger , Andrey Ryabinin , Andrew Morton , Dmitry Vyukov , Mathieu Desnoyers Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 2020-05-11 at 11:05 -0700, Paul E. McKenney wrote: > On Mon, May 11, 2020 at 10:31:11AM +0800, Walter Wu wrote: > > This feature will record first and last call_rcu() call stack and > > print two call_rcu() call stack in KASAN report. > > Suppose that a given rcu_head structure is passed to call_rcu(), then > the grace period elapses, the callback is invoked, and the enclosing > data structure is freed. But then that same region of memory is > immediately reallocated as the same type of structure and again > passed to call_rcu(), and that this cycle repeats several times. > > Would the first call stack forever be associated with the first > call_rcu() in this series? If so, wouldn't the last two usually > be the most useful? Or am I unclear on the use case? > The first call stack doesn't forever associate with first call_rcu(), if someone object freed and reallocated, then the first call stack will replace with new object. > > 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 > > Suggested-by: Dmitry Vyukov > > Cc: Andrey Ryabinin > > Cc: Dmitry Vyukov > > Cc: Alexander Potapenko > > Cc: Andrew Morton > > Cc: Paul E. McKenney > > Cc: Josh Triplett > > Cc: Mathieu Desnoyers > > Cc: Lai Jiangshan > > Cc: Joel Fernandes > > --- > > 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 > > #include > > #include > > +#include > > #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); > > Just for the record, at this point we have not yet queued the callback. > We have also not yet disabled interrupts. Which might be OK, but I > figured I should call out the possibility of moving this down a few > lines to follow the local_irq_save(). > We will intend to do it. > If someone incorrectly invokes concurrently invokes call_rcu() on this > same region of memory, possibly from an interrupt handler, we are OK > corrupting the stack traces, right? > Yes, and the wrong invoking call_rcu should be recorded. > But what happens if a given structure has more than one rcu_head > structure? In that case, RCU would be just fine with it being > concurrently passed to different call_rcu() invocations as long as the > two invocations didn't both use the same rcu_head structure. (In that > case, they had best not be both freeing the object, and if even one of > them is freeing the object, coordination is necessary.) > > If this is a problem, one approach would be to move the > kasan_record_aux_stack(head) call to kfree_rcu(). After all, it is > definitely illegal to pass the same memory to a pair of kfree_rcu() > invocations! ;-) > The function of kasan_record_aux_stack(head) is simple, it is only to record call stack by the 'head' object. Thanks. > Thanx, Paul > > > + > > /* 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); > > +} > > 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); > > -- > I> 2.18.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel