From mboxrd@z Thu Jan 1 00:00:00 1970 From: Walter Wu Subject: Re: [PATCH] kasan: fix the missing underflow in memmove and memcpy with CONFIG_KASAN_GENERIC=y Date: Fri, 27 Sep 2019 22:22:22 +0800 Message-ID: <1569594142.9045.24.camel@mtksdccf07> References: <20190927034338.15813-1-walter-zh.wu@mediatek.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Dmitry Vyukov Cc: Andrey Ryabinin , Alexander Potapenko , Matthias Brugger , LKML , kasan-dev , Linux-MM , Linux ARM , linux-mediatek@lists.infradead.org, wsd_upstream List-Id: linux-mediatek@lists.infradead.org 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 <= size < 0, then KASAN will miss to catch the underflow issue. > > 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 = 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=199341 > > > > 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_memset(void) > > kfree(ptr); > > } > > > > +static noinline void __init kmalloc_oob_in_memmove_underflow(void) > > +{ > > + char *ptr; > > + size_t size = 64; > > + > > + pr_info("underflow out-of-bounds in memmove\n"); > > + ptr = 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 = 64; > > + > > + pr_info("overflow out-of-bounds in memmove\n"); > > + ptr = 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 = kasan_mem_to_shadow((void *)addr); > > + void *shadow_end = kasan_mem_to_shadow((void *)addr + size - 1) + 1; > > > > - ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr), > > - kasan_mem_to_shadow((void *)addr + size - 1) + 1); > > + if ((long)size < 0) > > + shadow_end = kasan_mem_to_shadow((void *)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 immediately if size<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’s doing the following.or? void *memmove(void *dest, const void *src, size_t len) { + if (long(len) <= 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_); 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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, 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 DAA9AC4360C for ; Fri, 27 Sep 2019 14:22:44 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org 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Date:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=tEcluA0W9Zlj1Ec24V2G6YJS8mZETJ1FD49xuTYj8fo=; b=c7wmWrQHV8hvIo KZReouI9X5iuC8ui6zS+dP3PD6iKoxgVINMv/OMr7BLrEJEzm1mK97gNQlSwJsISQ+eb0Azc5Vzfy nG+KIsyu1jzqX4mkIo33YeZOs1SemW+z2BpbG14ioz6115MkUHo/GX7uY8XgF9LZfqQ1iYgacGcX8 dVTko6YrgxvHP2aEhnBvJwGPcq9J1DRFrr//QxMRPEJlBvTJidxwmZimenbHYHeekv8Un2uFT5hQ/ A4cKelle/PEqNx8m8zEIsMUipf9gX7m/4koai7OOlO+mVKE2eF4WPNMIl99KWjF3a5FyLlq9frPhq KA70LvOB8FBrU9N6l2fQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iDr8l-0003V2-7Q; Fri, 27 Sep 2019 14:22:35 +0000 Received: from mailgw02.mediatek.com ([216.200.240.185]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1iDr8h-0003TY-Gb; Fri, 27 Sep 2019 14:22:33 +0000 X-UUID: d90e4749f4f749afb4c90e01ca4a3488-20190927 X-UUID: d90e4749f4f749afb4c90e01ca4a3488-20190927 Received: from mtkcas66.mediatek.inc [(172.29.193.44)] by mailgw02.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLS) with ESMTP id 388489; Fri, 27 Sep 2019 06:22:22 -0800 Received: from MTKMBS07N2.mediatek.inc (172.21.101.141) by MTKMBS62DR.mediatek.inc (172.29.94.18) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Fri, 27 Sep 2019 07:22:21 -0700 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 Date: Fri, 27 Sep 2019 22:22:22 +0800 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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_);