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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,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 32D05C388F3 for ; Fri, 27 Sep 2019 14:22:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6AD11217D9 for ; Fri, 27 Sep 2019 14:22:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6AD11217D9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=mediatek.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B920C8E0005; Fri, 27 Sep 2019 10:22:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B42248E0001; Fri, 27 Sep 2019 10:22:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A31148E0005; Fri, 27 Sep 2019 10:22:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0113.hostedemail.com [216.40.44.113]) by kanga.kvack.org (Postfix) with ESMTP id 7AFF98E0001 for ; Fri, 27 Sep 2019 10:22:30 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id E4EA5180AD802 for ; Fri, 27 Sep 2019 14:22:29 +0000 (UTC) X-FDA: 75980916018.28.mark13_159e7dfc9ad4c X-HE-Tag: mark13_159e7dfc9ad4c X-Filterd-Recvd-Size: 7072 Received: from mailgw02.mediatek.com (unknown [210.61.82.184]) by imf23.hostedemail.com (Postfix) with ESMTP for ; Fri, 27 Sep 2019 14:22:28 +0000 (UTC) X-UUID: 5969bb150a984d08adde2d2ffdd3d229-20190927 X-UUID: 5969bb150a984d08adde2d2ffdd3d229-20190927 Received: from mtkexhb02.mediatek.inc [(172.21.101.103)] by mailgw02.mediatek.com (envelope-from ) (Cellopoint E-mail Firewall v4.1.10 Build 0809 with TLS) with ESMTP id 399212952; Fri, 27 Sep 2019 22:22:23 +0800 Received: from mtkcas07.mediatek.inc (172.21.101.84) by mtkmbs07n2.mediatek.inc (172.21.101.141) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Fri, 27 Sep 2019 22:22:19 +0800 Received: from [172.21.84.99] (172.21.84.99) by mtkcas07.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Fri, 27 Sep 2019 22:22:19 +0800 Message-ID: <1569594142.9045.24.camel@mtksdccf07> Subject: Re: [PATCH] kasan: fix the missing underflow in memmove and memcpy with CONFIG_KASAN_GENERIC=y From: Walter Wu To: Dmitry Vyukov CC: Andrey Ryabinin , Alexander Potapenko , Matthias Brugger , LKML , kasan-dev , Linux-MM , Linux ARM , , wsd_upstream Date: Fri, 27 Sep 2019 22:22:22 +0800 In-Reply-To: References: <20190927034338.15813-1-walter-zh.wu@mediatek.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-MTK: N Content-Transfer-Encoding: quoted-printable 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, 2019-09-27 at 15:07 +0200, Dmitry Vyukov wrote: > On Fri, Sep 27, 2019 at 5:43 AM Walter Wu w= rote: > > > > memmove() and memcpy() have missing underflow issues. > > When -7 <=3D size < 0, then KASAN will miss to catch the underflow is= sue. > > It looks like shadow start address and shadow end address is the same= , > > so it does not actually check anything. > > > > The following test is indeed not caught by KASAN: > > > > char *p =3D kmalloc(64, GFP_KERNEL); > > memset((char *)p, 0, 64); > > memmove((char *)p, (char *)p + 4, -2); > > kfree((char*)p); > > > > It should be checked here: > > > > void *memmove(void *dest, const void *src, size_t len) > > { > > check_memory_region((unsigned long)src, len, false, _RET_IP_)= ; > > check_memory_region((unsigned long)dest, len, true, _RET_IP_)= ; > > > > return __memmove(dest, src, len); > > } > > > > We fix the shadow end address which is calculated, then generic KASAN > > get the right shadow end address and detect this underflow issue. > > > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=3D199341 > > > > Signed-off-by: Walter Wu > > Reported-by: Dmitry Vyukov > > --- > > lib/test_kasan.c | 36 ++++++++++++++++++++++++++++++++++++ > > mm/kasan/generic.c | 8 ++++++-- > > 2 files changed, 42 insertions(+), 2 deletions(-) > > > > diff --git a/lib/test_kasan.c b/lib/test_kasan.c > > index b63b367a94e8..8bd014852556 100644 > > --- a/lib/test_kasan.c > > +++ b/lib/test_kasan.c > > @@ -280,6 +280,40 @@ static noinline void __init kmalloc_oob_in_memse= t(void) > > kfree(ptr); > > } > > > > +static noinline void __init kmalloc_oob_in_memmove_underflow(void) > > +{ > > + char *ptr; > > + size_t size =3D 64; > > + > > + pr_info("underflow out-of-bounds in memmove\n"); > > + ptr =3D kmalloc(size, GFP_KERNEL); > > + if (!ptr) { > > + pr_err("Allocation failed\n"); > > + return; > > + } > > + > > + memset((char *)ptr, 0, 64); > > + memmove((char *)ptr, (char *)ptr + 4, -2); > > + kfree(ptr); > > +} > > + > > +static noinline void __init kmalloc_oob_in_memmove_overflow(void) > > +{ > > + char *ptr; > > + size_t size =3D 64; > > + > > + pr_info("overflow out-of-bounds in memmove\n"); > > + ptr =3D kmalloc(size, GFP_KERNEL); > > + if (!ptr) { > > + pr_err("Allocation failed\n"); > > + return; > > + } > > + > > + memset((char *)ptr, 0, 64); > > + memmove((char *)ptr + size, (char *)ptr, 2); > > + kfree(ptr); > > +} > > + > > static noinline void __init kmalloc_uaf(void) > > { > > char *ptr; > > @@ -734,6 +768,8 @@ static int __init kmalloc_tests_init(void) > > kmalloc_oob_memset_4(); > > kmalloc_oob_memset_8(); > > kmalloc_oob_memset_16(); > > + kmalloc_oob_in_memmove_underflow(); > > + kmalloc_oob_in_memmove_overflow(); > > kmalloc_uaf(); > > kmalloc_uaf_memset(); > > kmalloc_uaf2(); > > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > > index 616f9dd82d12..34ca23d59e67 100644 > > --- a/mm/kasan/generic.c > > +++ b/mm/kasan/generic.c > > @@ -131,9 +131,13 @@ static __always_inline bool memory_is_poisoned_n= (unsigned long addr, > > size_t size) > > { > > unsigned long ret; > > + void *shadow_start =3D kasan_mem_to_shadow((void *)addr); > > + void *shadow_end =3D kasan_mem_to_shadow((void *)addr + size = - 1) + 1; > > > > - ret =3D memory_is_nonzero(kasan_mem_to_shadow((void *)addr), > > - kasan_mem_to_shadow((void *)addr + size - 1) = + 1); > > + if ((long)size < 0) > > + shadow_end =3D kasan_mem_to_shadow((void *)addr + siz= e); >=20 > Hi Walter, >=20 > Thanks for working on this. >=20 > If size<0, does it make sense to continue at all? We will still check > 1PB of shadow memory? What happens when we pass such huge range to > memory_is_nonzero? > Perhaps it's better to produce an error and bail out immediately if siz= e<0? I agree with what you said. when size<0, it is indeed an unreasonable behavior, it should be blocked from continuing to do. > Also, what's the failure mode of the tests? Didn't they badly corrupt > memory? We tried to keep tests such that they produce the KASAN > reports, but don't badly corrupt memory b/c/ we need to run all of > them. Maybe we should first produce KASAN reports and then go to execute memmove() or do nothing? It looks like it=E2=80=99s doing the following.o= r? void *memmove(void *dest, const void *src, size_t len) { + if (long(len) <=3D 0) + kasan_report_invalid_size(src, dest, len, _RET_IP_); + check_memory_region((unsigned long)src, len, false, _RET_IP_); check_memory_region((unsigned long)dest, len, true, _RET_IP_);