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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 EC05DC47423 for ; Thu, 1 Oct 2020 18:03:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 541FD208B6 for ; Thu, 1 Oct 2020 18:03:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="g857Ar4O" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 541FD208B6 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A3D97900024; Thu, 1 Oct 2020 14:03:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9ED02900003; Thu, 1 Oct 2020 14:03:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8DCFE900024; Thu, 1 Oct 2020 14:03:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0136.hostedemail.com [216.40.44.136]) by kanga.kvack.org (Postfix) with ESMTP id 6376E900003 for ; Thu, 1 Oct 2020 14:03:38 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E649D181AC550 for ; Thu, 1 Oct 2020 18:03:37 +0000 (UTC) X-FDA: 77324129274.26.mom12_33137ec2719d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id B5FF81804B65C for ; Thu, 1 Oct 2020 18:03:37 +0000 (UTC) X-HE-Tag: mom12_33137ec2719d X-Filterd-Recvd-Size: 9477 Received: from mail-wm1-f66.google.com (mail-wm1-f66.google.com [209.85.128.66]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Thu, 1 Oct 2020 18:03:36 +0000 (UTC) Received: by mail-wm1-f66.google.com with SMTP id w2so3837984wmi.1 for ; Thu, 01 Oct 2020 11:03:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=4RuJhY/87VL3JhPEf+faiXyRb2FdU2wNNWjiTAoQeOk=; b=g857Ar4OsKkfvKJF2TeGJcsn2rzY1dIr/DaETOmxqkjGRsvrERpsZ1x0BXqG9/hwgp a74u3LiD8RkIwlbIEjQLlt6wGSecAk4o7qfoR6Ds8UO2dK88PYWOB/hmazDeRJDAA+BI Nfj7WVFZOY76x4b5/p2zJHgR/zkQ+zowJze7ZEiMnuHRKDT/jbT3Cfjlxcyki0PSfiK0 vgPUSw5Zzi1rTfbHxIHGM2l9o2IWC0FgNoYqOo4v+ski0leEakl9n5UmBkE2X+jDFT/S 8L3c6PiJXfzRiBA5JXaNFdzKBNJ2XsQr6ngC/h4st9mXATqasL8kkewWSYZwszEogLpc 52Hw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=4RuJhY/87VL3JhPEf+faiXyRb2FdU2wNNWjiTAoQeOk=; b=RAhfD3Fk50LGC1cWuM+JWPj7KC1VNSz2e3fkxpqe7QnmeF1nluR8dBBMODz09uuhG6 pJEAUz6hXaSBiFnXE8Fs6ybiFXjUURTq4I8N6Bi0gQ8fDSBmLPOBEy2R9PHjYruRsfWO +OMWCLmaetM2i2LPK6EZ84v2WXMNON8eatRx/NfzpD5tLLl4J6+WQVwBW8FKTN8N4NN6 aPKxEJhnLAA3c1p5BcR5aOzCCy7gGIduN9j82y108BKVJDe2ADK5wF6BYm55QtC/+/sM ow2flCsg6XknzMS76HbPjwiaeobGQiOc3MZ0Y5UPBZlMh5QgVptRZglCr5R5qFf5m6yB Izqg== X-Gm-Message-State: AOAM531GhzibsExV2yQfEF6dj073xtblqdF3cAvvNuS0nxgEmdsGySaF GfCR8S8ZTcBebHZGDbsBkVP1rg== X-Google-Smtp-Source: ABdhPJw7xuBgltMVA48qRrl2OpqGXsDqBxsHXhWfgM2MZ/UBkevUn68H+Zo3O/HFZuEwfmRkQZH0XQ== X-Received: by 2002:a1c:b7d7:: with SMTP id h206mr1284905wmf.159.1601575415423; Thu, 01 Oct 2020 11:03:35 -0700 (PDT) Received: from elver.google.com ([100.105.32.75]) by smtp.gmail.com with ESMTPSA id t4sm10525373wrr.26.2020.10.01.11.03.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2020 11:03:34 -0700 (PDT) Date: Thu, 1 Oct 2020 20:03:29 +0200 From: elver@google.com To: Andrey Konovalov Cc: Dmitry Vyukov , Vincenzo Frascino , Catalin Marinas , kasan-dev@googlegroups.com, Andrey Ryabinin , Alexander Potapenko , Evgenii Stepanov , Elena Petrova , Branislav Rankov , Kevin Brodsky , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 37/39] kasan, slub: reset tags when accessing metadata Message-ID: <20201001180329.GV4162920@elver.google.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.14.5 (2020-06-23) 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 Fri, Sep 25, 2020 at 12:50AM +0200, Andrey Konovalov wrote: > SLUB allocator accesses metadata for slab objects, that may lie > out-of-bounds of the object itself, or be accessed when an object is freed. > Such accesses trigger tag faults and lead to false-positive reports with > hardware tag-based KASAN. > > Software KASAN modes disable instrumentation for allocator code via > KASAN_SANITIZE Makefile macro, and rely on kasan_enable/disable_current() > annotations which are used to ignore KASAN reports. > > With hardware tag-based KASAN neither of those options are available, as > it doesn't use compiler instrumetation, no tag faults are ignored, and MTE > is disabled after the first one. > > Instead, reset tags when accessing metadata. > > Signed-off-by: Andrey Konovalov > Signed-off-by: Vincenzo Frascino Acked-by: Marco Elver I assume you have tested with the various SLUB debug options, as well as things like memory initialization etc? > --- > Change-Id: I39f3c4d4f29299d4fbbda039bedf230db1c746fb > --- > mm/page_poison.c | 2 +- > mm/slub.c | 25 ++++++++++++++----------- > 2 files changed, 15 insertions(+), 12 deletions(-) > > diff --git a/mm/page_poison.c b/mm/page_poison.c > index 34b9181ee5d1..d90d342a391f 100644 > --- a/mm/page_poison.c > +++ b/mm/page_poison.c > @@ -43,7 +43,7 @@ static void poison_page(struct page *page) > > /* KASAN still think the page is in-use, so skip it. */ > kasan_disable_current(); > - memset(addr, PAGE_POISON, PAGE_SIZE); > + memset(kasan_reset_tag(addr), PAGE_POISON, PAGE_SIZE); > kasan_enable_current(); > kunmap_atomic(addr); > } > diff --git a/mm/slub.c b/mm/slub.c > index 68c02b2eecd9..f5b4bef3cd6c 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -249,7 +249,7 @@ static inline void *freelist_ptr(const struct kmem_cache *s, void *ptr, > { > #ifdef CONFIG_SLAB_FREELIST_HARDENED > /* > - * When CONFIG_KASAN_SW_TAGS is enabled, ptr_addr might be tagged. > + * When CONFIG_KASAN_SW/HW_TAGS is enabled, ptr_addr might be tagged. > * Normally, this doesn't cause any issues, as both set_freepointer() > * and get_freepointer() are called with a pointer with the same tag. > * However, there are some issues with CONFIG_SLUB_DEBUG code. For > @@ -275,6 +275,7 @@ static inline void *freelist_dereference(const struct kmem_cache *s, > > static inline void *get_freepointer(struct kmem_cache *s, void *object) > { > + object = kasan_reset_tag(object); > return freelist_dereference(s, object + s->offset); > } > > @@ -304,6 +305,7 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp) > BUG_ON(object == fp); /* naive detection of double free or corruption */ > #endif > > + freeptr_addr = (unsigned long)kasan_reset_tag((void *)freeptr_addr); > *(void **)freeptr_addr = freelist_ptr(s, fp, freeptr_addr); > } > > @@ -538,8 +540,8 @@ static void print_section(char *level, char *text, u8 *addr, > unsigned int length) > { > metadata_access_enable(); > - print_hex_dump(level, text, DUMP_PREFIX_ADDRESS, 16, 1, addr, > - length, 1); > + print_hex_dump(level, kasan_reset_tag(text), DUMP_PREFIX_ADDRESS, > + 16, 1, addr, length, 1); > metadata_access_disable(); > } > > @@ -570,7 +572,7 @@ static struct track *get_track(struct kmem_cache *s, void *object, > > p = object + get_info_end(s); > > - return p + alloc; > + return kasan_reset_tag(p + alloc); > } > > static void set_track(struct kmem_cache *s, void *object, > @@ -583,7 +585,8 @@ static void set_track(struct kmem_cache *s, void *object, > unsigned int nr_entries; > > metadata_access_enable(); > - nr_entries = stack_trace_save(p->addrs, TRACK_ADDRS_COUNT, 3); > + nr_entries = stack_trace_save(kasan_reset_tag(p->addrs), > + TRACK_ADDRS_COUNT, 3); > metadata_access_disable(); > > if (nr_entries < TRACK_ADDRS_COUNT) > @@ -747,7 +750,7 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page, > > static void init_object(struct kmem_cache *s, void *object, u8 val) > { > - u8 *p = object; > + u8 *p = kasan_reset_tag(object); > > if (s->flags & SLAB_RED_ZONE) > memset(p - s->red_left_pad, val, s->red_left_pad); > @@ -777,7 +780,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page, > u8 *addr = page_address(page); > > metadata_access_enable(); > - fault = memchr_inv(start, value, bytes); > + fault = memchr_inv(kasan_reset_tag(start), value, bytes); > metadata_access_disable(); > if (!fault) > return 1; > @@ -873,7 +876,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page) > > pad = end - remainder; > metadata_access_enable(); > - fault = memchr_inv(pad, POISON_INUSE, remainder); > + fault = memchr_inv(kasan_reset_tag(pad), POISON_INUSE, remainder); > metadata_access_disable(); > if (!fault) > return 1; > @@ -1118,7 +1121,7 @@ void setup_page_debug(struct kmem_cache *s, struct page *page, void *addr) > return; > > metadata_access_enable(); > - memset(addr, POISON_INUSE, page_size(page)); > + memset(kasan_reset_tag(addr), POISON_INUSE, page_size(page)); > metadata_access_disable(); > } > > @@ -2884,10 +2887,10 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, > stat(s, ALLOC_FASTPATH); > } > > - maybe_wipe_obj_freeptr(s, object); > + maybe_wipe_obj_freeptr(s, kasan_reset_tag(object)); > > if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object) > - memset(object, 0, s->object_size); > + memset(kasan_reset_tag(object), 0, s->object_size); > > slab_post_alloc_hook(s, objcg, gfpflags, 1, &object); > > -- > 2.28.0.681.g6f77f65b4e-goog >