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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB481C433EF for ; Mon, 14 Mar 2022 07:17:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 48E988D0005; Mon, 14 Mar 2022 03:17:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 43DE48D0001; Mon, 14 Mar 2022 03:17:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 305988D0005; Mon, 14 Mar 2022 03:17:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 236B68D0001 for ; Mon, 14 Mar 2022 03:17:58 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id DCD3C246CF for ; Mon, 14 Mar 2022 07:17:57 +0000 (UTC) X-FDA: 79242137394.03.6D0FD6E Received: from mail-oo1-f42.google.com (mail-oo1-f42.google.com [209.85.161.42]) by imf21.hostedemail.com (Postfix) with ESMTP id 5BD6D1C0027 for ; Mon, 14 Mar 2022 07:17:57 +0000 (UTC) Received: by mail-oo1-f42.google.com with SMTP id r41-20020a4a966c000000b0031bf85a4124so19180404ooi.0 for ; Mon, 14 Mar 2022 00:17:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jHOQpg8FkWZ2D9kBQlZqUsUw9/chXLkk2DroGgT0P6g=; b=D8uyMk8EnZyrQebikWLVsUrSAQ3/m4z2B+4pBphbGlSeumCFVFgChQOnndtr+hsxbs glD2lvbM8w/3KYaxR4/C6UY0oPJkjJMjjZ6+JOcTmE9DFfQ0OmC9vYHb/mfDdSn7g0pA 7ZRHdmeFlBoEKnuzQ1RujYEop8rvsU5L/lUdlzq50s49dKp7iL1tfGl9bHfjEjftI2Ea Hbd1fo1LqSgTkO8bIWg+Ldfl3m0Hs9Sm0v+iFY3CKi754l2YSKRJU3j88E422TsRYu6D euIIE/UdykRfsOsp4T7Ev9LSQhzfnIchrMKzYeCg635pg5kOtMHrkurw0DIf5cQLp9J6 cUEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=jHOQpg8FkWZ2D9kBQlZqUsUw9/chXLkk2DroGgT0P6g=; b=00XuLH1Lrcv/YwA12HHvhP9JkQe9qJsTJzpBd9hC6F0Dq1oMbN57baH0sjoovpt3w4 VrWXm1QSVOy4vl1X59rWWNhz6AS/UiS1vH7S+kjVSN/iBj/L30AC9FQRv5H8QP76eluf Q2tf7dkE8yJo1mKGa7/+qvMcc1Lc+QbrStOc3G5c43AISbDImIIIIwTJgyjCpUP4AEVK 1hOJ6hX7EajNjHqRGwP2LdClONyp/wtxzmSSR8Tzf9KBCpacTGtbf58qlGK3RWkccn9P kLHMxqDXTDKZThHBTFSmeBOsY4zQjK+W1hdU2RPQQ3v92b/0l2bYL6QbdGWt6KO/XQ06 TkWw== X-Gm-Message-State: AOAM5338E6MARPXolZbHph2N2VM8ZYroSpIA5Vpm7wFqofJyt/3kozJN kv1lgAQo+Y3sU9/XtidGib2aprq9VtQG/z5hN1w7kw== X-Google-Smtp-Source: ABdhPJxZzWSTp4Q29wwMglz9UECVgKI7boAwwWTzT2TcroMKkNO0G1DuWKP9+Bq4ecaa8ZZg0fmogpTG2qFn/HGkArc= X-Received: by 2002:a05:6870:9619:b0:d9:a25e:ed55 with SMTP id d25-20020a056870961900b000d9a25eed55mr10310764oaq.163.1647242276344; Mon, 14 Mar 2022 00:17:56 -0700 (PDT) MIME-Version: 1.0 References: <57133fafc4d74377a4a08d98e276d58fe4a127dc.1647115974.git.andreyknvl@google.com> In-Reply-To: <57133fafc4d74377a4a08d98e276d58fe4a127dc.1647115974.git.andreyknvl@google.com> From: Dmitry Vyukov Date: Mon, 14 Mar 2022 08:17:45 +0100 Message-ID: Subject: Re: [PATCH] kasan, scs: collect stack traces from shadow stack To: andrey.konovalov@linux.dev Cc: Marco Elver , Alexander Potapenko , Andrew Morton , Andrey Konovalov , Andrey Ryabinin , kasan-dev@googlegroups.com, Vincenzo Frascino , Catalin Marinas , Will Deacon , Mark Rutland , Sami Tolvanen , Peter Collingbourne , Evgenii Stepanov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Konovalov Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5BD6D1C0027 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=D8uyMk8E; spf=pass (imf21.hostedemail.com: domain of dvyukov@google.com designates 209.85.161.42 as permitted sender) smtp.mailfrom=dvyukov@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspam-User: X-Stat-Signature: p6oidxt76fsfyec3w8oija8kb6dmcgqr X-HE-Tag: 1647242277-135403 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, 12 Mar 2022 at 21:14, wrote: > > From: Andrey Konovalov > > Currently, KASAN always uses the normal stack trace collection routines, > which rely on the unwinder, when saving alloc and free stack traces. > > Instead of invoking the unwinder, collect the stack trace by copying > frames from the Shadow Call Stack whenever it is enabled. This reduces > boot time by 30% for all KASAN modes when Shadow Call Stack is enabled. > > To avoid potentially leaking PAC pointer tags, strip them when saving > the stack trace. > > Signed-off-by: Andrey Konovalov > > --- > > Things to consider: > > We could integrate shadow stack trace collection into kernel/stacktrace.c > as e.g. stack_trace_save_shadow(). However, using stack_trace_consume_fn > leads to invoking a callback on each saved from, which is undesirable. > The plain copy loop is faster. > > We could add a command line flag to switch between stack trace collection > modes. I noticed that Shadow Call Stack might be missing certain frames > in stacks originating from a fault that happens in the middle of a > function. I am not sure if this case is important to handle though. > > Looking forward to thoughts and comments. > > Thanks! > > --- > mm/kasan/common.c | 36 +++++++++++++++++++++++++++++++++++- > 1 file changed, 35 insertions(+), 1 deletion(-) > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index d9079ec11f31..65a0723370c7 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -9,6 +9,7 @@ > * Andrey Konovalov > */ > > +#include > #include > #include > #include > @@ -21,6 +22,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -30,12 +32,44 @@ > #include "kasan.h" > #include "../slab.h" > > +#ifdef CONFIG_SHADOW_CALL_STACK > + > +#ifdef CONFIG_ARM64_PTR_AUTH > +#define PAC_TAG_RESET(x) (x | GENMASK(63, CONFIG_ARM64_VA_BITS)) > +#else > +#define PAC_TAG_RESET(x) (x) > +#endif > + > +static unsigned int save_shadow_stack(unsigned long *entries, > + unsigned int nr_entries) > +{ > + unsigned long *scs_sp = task_scs_sp(current); > + unsigned long *scs_base = task_scs(current); Just to double-check: interrupt frames are also appended to the the current task buffer, right? > + unsigned long *frame; > + unsigned int i = 0; > + > + for (frame = scs_sp - 1; frame >= scs_base; frame--) { > + entries[i++] = PAC_TAG_RESET(*frame); > + if (i >= nr_entries) > + break; > + } > + > + return i; > +} > +#else /* CONFIG_SHADOW_CALL_STACK */ > +static inline unsigned int save_shadow_stack(unsigned long *entries, > + unsigned int nr_entries) { return 0; } > +#endif /* CONFIG_SHADOW_CALL_STACK */ > + > depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc) > { > unsigned long entries[KASAN_STACK_DEPTH]; > unsigned int nr_entries; > > - nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); > + if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) > + nr_entries = save_shadow_stack(entries, ARRAY_SIZE(entries)); > + else > + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); > return __stack_depot_save(entries, nr_entries, flags, can_alloc); > } > > -- > 2.25.1 >