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 42418C10F14 for ; Thu, 3 Oct 2019 09:38:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E2290218DE for ; Thu, 3 Oct 2019 09:38:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E2290218DE 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 8C3B56B0005; Thu, 3 Oct 2019 05:38:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 873E38E0005; Thu, 3 Oct 2019 05:38:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 73C108E0003; Thu, 3 Oct 2019 05:38:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0005.hostedemail.com [216.40.44.5]) by kanga.kvack.org (Postfix) with ESMTP id 5291D6B0005 for ; Thu, 3 Oct 2019 05:38:52 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id D4F246107 for ; Thu, 3 Oct 2019 09:38:51 +0000 (UTC) X-FDA: 76001974062.10.rock77_4d228fe09d10d X-HE-Tag: rock77_4d228fe09d10d X-Filterd-Recvd-Size: 14138 Received: from mailgw02.mediatek.com (unknown [210.61.82.184]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Thu, 3 Oct 2019 09:38:49 +0000 (UTC) X-UUID: 83d216c888f543e887d8043adfa60921-20191003 X-UUID: 83d216c888f543e887d8043adfa60921-20191003 Received: from mtkcas08.mediatek.inc [(172.21.101.126)] by mailgw02.mediatek.com (envelope-from ) (Cellopoint E-mail Firewall v4.1.10 Build 0809 with TLS) with ESMTP id 1843083875; Thu, 03 Oct 2019 17:38:46 +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; Thu, 3 Oct 2019 17:38:43 +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; Thu, 3 Oct 2019 17:38:44 +0800 Message-ID: <1570095525.19702.59.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: Thu, 3 Oct 2019 17:38:45 +0800 In-Reply-To: References: <20190927034338.15813-1-walter-zh.wu@mediatek.com> <1569594142.9045.24.camel@mtksdccf07> <1569818173.17361.19.camel@mtksdccf07> <1570018513.19702.36.camel@mtksdccf07> <1570069078.19702.57.camel@mtksdccf07> 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 Thu, 2019-10-03 at 08:26 +0200, Dmitry Vyukov wrote: > On Thu, Oct 3, 2019 at 4:18 AM Walter Wu wr= ote: > > > > On Wed, 2019-10-02 at 15:57 +0200, Dmitry Vyukov wrote: > > > On Wed, Oct 2, 2019 at 2:15 PM Walter Wu wrote: > > > > > > > > On Mon, 2019-09-30 at 12:36 +0800, Walter Wu wrote: > > > > > On Fri, 2019-09-27 at 21:41 +0200, Dmitry Vyukov wrote: > > > > > > On Fri, Sep 27, 2019 at 4:22 PM Walter Wu wrote: > > > > > > > > > > > > > > On Fri, 2019-09-27 at 15:07 +0200, Dmitry Vyukov wrote: > > > > > > > > On Fri, Sep 27, 2019 at 5:43 AM Walter Wu wrote: > > > > > > > > > > > > > > > > > > memmove() and memcpy() have missing underflow issues. > > > > > > > > > When -7 <=3D size < 0, then KASAN will miss to catch th= e underflow issue. > > > > > > > > > It looks like shadow start address and shadow end addre= ss 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, fa= lse, _RET_IP_); > > > > > > > > > check_memory_region((unsigned long)dest, len, t= rue, _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 underf= low issue. > > > > > > > > > > > > > > > > > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=3D19934= 1 > > > > > > > > > > > > > > > > > > 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 kmallo= c_oob_in_memset(void) > > > > > > > > > kfree(ptr); > > > > > > > > > } > > > > > > > > > > > > > > > > > > +static noinline void __init kmalloc_oob_in_memmove_und= erflow(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_ove= rflow(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_ini= t(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((voi= d *)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 *)add= r + size - 1) + 1); > > > > > > > > > + if ((long)size < 0) > > > > > > > > > + shadow_end =3D kasan_mem_to_shadow((voi= d *)addr + size); > > > > > > > > > > > > > > > > Hi Walter, > > > > > > > > > > > > > > > > Thanks for working on this. > > > > > > > > > > > > > > > > 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 imme= diately if size<0? > > > > > > > > > > > > > > I agree with what you said. when size<0, it is indeed an un= reasonable > > > > > > > behavior, it should be blocked from continuing to do. > > > > > > > > > > > > > > > > > > > > > > Also, what's the failure mode of the tests? Didn't they b= adly 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 r= un 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 t= he following.or? > > > > > > > > > > > > > > void *memmove(void *dest, const void *src, size_t len) > > > > > > > { > > > > > > > + if (long(len) <=3D 0) > > > > > > > > > > > > /\/\/\/\/\/\ > > > > > > > > > > > > This check needs to be inside of check_memory_region, otherwi= se we > > > > > > will have similar problems in all other places that use > > > > > > check_memory_region. > > > > > Thanks for your reminder. > > > > > > > > > > bool check_memory_region(unsigned long addr, size_t size, bool= write, > > > > > unsigned long ret_ip) > > > > > { > > > > > + if (long(size) < 0) { > > > > > + kasan_report_invalid_size(src, dest, len, _RET_= IP_); > > > > > + return false; > > > > > + } > > > > > + > > > > > return check_memory_region_inline(addr, size, write, re= t_ip); > > > > > } > > > > > > > > > > > But check_memory_region already returns a bool, so we could c= heck that > > > > > > bool and return early. > > > > > > > > > > When size<0, we should only show one KASAN report, and should w= e only > > > > > limit to return when size<0 is true? If yse, then __memmove() w= ill do > > > > > nothing. > > > > > > > > > > > > > > > void *memmove(void *dest, const void *src, size_t len) > > > > > { > > > > > - check_memory_region((unsigned long)src, len, false, _RE= T_IP_); > > > > > + if(!check_memory_region((unsigned long)src, len, false, > > > > > _RET_IP_) > > > > > + && long(size) < 0) > > > > > + return; > > > > > + > > > > > check_memory_region((unsigned long)dest, len, true, _RE= T_IP_); > > > > > > > > > > return __memmove(dest, src, len); > > > > > > > > > > > > > > > Hi Dmitry, > > > > > > > > What do you think the following code is better than the above one= . > > > > In memmmove/memset/memcpy, they need to determine whether size < = 0 is > > > > true. we directly determine whether size is negative in memmove a= nd > > > > return early. it avoid to generate repeated KASAN report. Is it b= etter? > > > > > > > > void *memmove(void *dest, const void *src, size_t len) > > > > { > > > > + if (long(size) < 0) { > > > > + kasan_report_invalid_size(src, dest, len, _RET_IP= _); > > > > + return; > > > > + } > > > > + > > > > check_memory_region((unsigned long)src, len, false, _RET_= IP_); > > > > check_memory_region((unsigned long)dest, len, true, _RET_= IP_); > > > > > > > > > > > > check_memory_region() still has to check whether the size is nega= tive. > > > > but memmove/memset/memcpy generate invalid size KASAN report will= not be > > > > there. > > > > > > > > > If check_memory_region() will do the check, why do we need to > > > duplicate it inside of memmove and all other range functions? > > > > > Yes, I know it has duplication, but if we don't have to determine siz= e<0 > > in memmove, then all check_memory_region return false will do nothing= , >=20 > But they will produce a KASAN report, right? They are asked to check > if 18446744073709551614 bytes are good. 18446744073709551614 bytes > can't be good. >=20 >=20 > > it includes other memory corruption behaviors, this is my original > > concern. > > > > > I would do: > > > > > > void *memmove(void *dest, const void *src, size_t len) > > > { > > > if (check_memory_region((unsigned long)src, len, false, _RE= T_IP_)) > > > return; > > if check_memory_region return TRUE is to do nothing, but it is no mem= ory > > corruption? Should it return early when check_memory_region return a > > FALSE? >=20 > Maybe. I just meant the overall idea: check_memory_region should > detect that 18446744073709551614 bytes are bad, print an error, return > an indication that bytes were bad, memmove should return early if the > range is bad. >=20 ok, i will send new patch. Thanks for your review. >=20 > > > This avoids duplicating the check, adds minimal amount of code to > > > range functions and avoids adding kasan_report_invalid_size. > > Thanks for your suggestion. > > We originally want to show complete information(destination address, > > source address, and its length), but add minimal amount of code into > > kasan_report(), it should be good. > > > > > > -- > > You received this message because you are subscribed to the Google Gr= oups "kasan-dev" group. > > To unsubscribe from this group and stop receiving emails from it, sen= d an email to kasan-dev+unsubscribe@googlegroups.com. > > To view this discussion on the web visit https://groups.google.com/d/= msgid/kasan-dev/1570069078.19702.57.camel%40mtksdccf07.