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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C708C433F5 for ; Tue, 30 Nov 2021 12:34:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241611AbhK3MiH (ORCPT ); Tue, 30 Nov 2021 07:38:07 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:33880 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229638AbhK3MiC (ORCPT ); Tue, 30 Nov 2021 07:38:02 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 5E19F1FD59; Tue, 30 Nov 2021 12:34:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1638275682; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fpzJzpUtUcBoti6u4Vx5MyjLRfI5xfFsHhW6Dr3Lcnw=; b=DpHiyHM2XViEBM4KfBrpR8vi43+dHuXUoqUN4Rz/0PdviP2Nz0MoV67Nf4aTOu1QB3ejlj noNin37l/OCjegAPe8Y+ovsl+Qrdulwj8QCMsSubl1mVOV1P5779H/HGe6/tzwbM/tiIvv KTv+1aYyn8zp9qe6VkgTMGEnQrbB7Ko= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1638275682; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fpzJzpUtUcBoti6u4Vx5MyjLRfI5xfFsHhW6Dr3Lcnw=; b=tIuNx6Tqh3yW0Dk8rpvwsrucH0KSqz7uF1jKvl52jXl6zJybsDC1GYMxlonxhSkman64bb 4zfb9pA7l6tRziBw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 1C1D613D04; Tue, 30 Nov 2021 12:34:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 6qowBmIapmGXeQAAMHmgww (envelope-from ); Tue, 30 Nov 2021 12:34:42 +0000 Message-ID: <37053057-1aa0-6ed3-7c84-c3eeb26cbcf1@suse.cz> Date: Tue, 30 Nov 2021 13:34:41 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH] lib/stackdepot: always do filter_irq_stacks() in stack_depot_save() Content-Language: en-US To: Marco Elver , Andrew Morton Cc: Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vijayanand Jitta , "Gustavo A. R. Silva" , Imran Khan , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Chris Wilson , Jani Nikula , Mika Kuoppala , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org References: <20211130095727.2378739-1-elver@google.com> From: Vlastimil Babka In-Reply-To: <20211130095727.2378739-1-elver@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/30/21 10:57, Marco Elver wrote: > The non-interrupt portion of interrupt stack traces before interrupt > entry is usually arbitrary. Therefore, saving stack traces of interrupts > (that include entries before interrupt entry) to stack depot leads to > unbounded stackdepot growth. > > As such, use of filter_irq_stacks() is a requirement to ensure > stackdepot can efficiently deduplicate interrupt stacks. > > Looking through all current users of stack_depot_save(), none (except > KASAN) pass the stack trace through filter_irq_stacks() before passing > it on to stack_depot_save(). > > Rather than adding filter_irq_stacks() to all current users of > stack_depot_save(), it became clear that stack_depot_save() should > simply do filter_irq_stacks(). Agree. > Signed-off-by: Marco Elver Acked-by: Vlastimil Babka Thanks. > --- > lib/stackdepot.c | 13 +++++++++++++ > mm/kasan/common.c | 1 - > 2 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/lib/stackdepot.c b/lib/stackdepot.c > index b437ae79aca1..519c7898c7f2 100644 > --- a/lib/stackdepot.c > +++ b/lib/stackdepot.c > @@ -305,6 +305,9 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); > * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids > * any allocations and will fail if no space is left to store the stack trace. > * > + * If the stack trace in @entries is from an interrupt, only the portion up to > + * interrupt entry is saved. > + * > * Context: Any context, but setting @can_alloc to %false is required if > * alloc_pages() cannot be used from the current context. Currently > * this is the case from contexts where neither %GFP_ATOMIC nor > @@ -323,6 +326,16 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, > unsigned long flags; > u32 hash; > > + /* > + * If this stack trace is from an interrupt, including anything before > + * interrupt entry usually leads to unbounded stackdepot growth. > + * > + * Because use of filter_irq_stacks() is a requirement to ensure > + * stackdepot can efficiently deduplicate interrupt stacks, always > + * filter_irq_stacks() to simplify all callers' use of stackdepot. > + */ > + nr_entries = filter_irq_stacks(entries, nr_entries); > + > if (unlikely(nr_entries == 0) || stack_depot_disable) > goto fast_exit; > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 8428da2aaf17..efaa836e5132 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -36,7 +36,6 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc) > unsigned int nr_entries; > > nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); > - nr_entries = filter_irq_stacks(entries, nr_entries); > return __stack_depot_save(entries, nr_entries, flags, can_alloc); > } > >