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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 74ECBC433EF for ; Fri, 10 Sep 2021 21:17:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0724E611BF for ; Fri, 10 Sep 2021 21:17:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0724E611BF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 883F5900002; Fri, 10 Sep 2021 17:17:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 833726B0072; Fri, 10 Sep 2021 17:17:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 72167900002; Fri, 10 Sep 2021 17:17:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0236.hostedemail.com [216.40.44.236]) by kanga.kvack.org (Postfix) with ESMTP id 62F496B0071 for ; Fri, 10 Sep 2021 17:17:50 -0400 (EDT) Received: from smtpin39.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 1DD3C18479694 for ; Fri, 10 Sep 2021 21:17:50 +0000 (UTC) X-FDA: 78572925900.39.FEA0FAE Received: from mail-io1-f46.google.com (mail-io1-f46.google.com [209.85.166.46]) by imf03.hostedemail.com (Postfix) with ESMTP id C117E3000099 for ; Fri, 10 Sep 2021 21:17:49 +0000 (UTC) Received: by mail-io1-f46.google.com with SMTP id y18so4105139ioc.1 for ; Fri, 10 Sep 2021 14:17:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=s7sAP/nJVXdZ6eZh6o+CtBX8yeYt6iONsuXDJwpxoK4=; b=ljNKLE+CX0o3u6CjVZP2hvUfk0bcrtB2FFtQhX2HAGR9I6wwNR6Hq1qnJajA9iE1HP naaWSFo+3fM2gV8kvgLY+9oK78wTnDjpBrVIFWo3K+8XM6J8bEZjqVpF4KL87AC4e5E2 n6b5bat3pemDrba1w1zYl5Ab1iVZrIS9MA01EsEj4BQHgcGgED1eKxOySnj+Quu9lPZC aZsmvYc9OBDqSuFV11zwaSSFZNboVI/FcvHsxpxMX1cFf78xN4viGvHp4E2WTRDiymYw 0QiPO5ZHERludqhd/4gR2nYAKCZyRhoLpKLZk+i6H/yhcdPvXZErh6QXDNdzjHmbc58I 2lIg== 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=s7sAP/nJVXdZ6eZh6o+CtBX8yeYt6iONsuXDJwpxoK4=; b=YrPqK3XmTbbKNOPJoWvH1lhVR6gXV11rpas4Xw/DITGXqy/lMHUXXH6dmHATnmc+pq EEW13OxzQzQ3PhAif9KPYjaXaRqsi17TBbQIoTxK3krnOMGIhLiBv+ylAhpLhGgQYTwj +zIztMJHP9ZbjIIZE2qTqLeSxb+m3qkayFvb3UbkSQbji/HFUComke5n2JhQayF54xNW RHR4CeFA6V6GDA4Vddq3ktJHGc4AgJIMA9Lz8eYw7HYhkUxj6vBymtNckprsW3CGDTIx 42GO7bu78vBI7fzEtisFT+QEafa0yTvNeVEu4s2kwJZJHjkmJzlViNO+Cmyt7abCR2lk cXRA== X-Gm-Message-State: AOAM530PMm18wtjCYCDaJSR+AAD6QhINOHdbRyjZepaPHUlJPp5pqgvc q3GDG2HHFwjQ/j5uQVcxRRMsmjxrZD9kQvg3iNJa5WbL5D4= X-Google-Smtp-Source: ABdhPJxlQeg3AzEnDvJLT6KdYpGk6tGRbXGgkrrmQ8OXpTcUp1WaEsVuccDC4dyky+3FYON4gzj/s1J4JK5FYSdJEPY= X-Received: by 2002:a5e:8e04:: with SMTP id a4mr8668218ion.56.1631308669095; Fri, 10 Sep 2021 14:17:49 -0700 (PDT) MIME-Version: 1.0 References: <20210910211356.3603758-1-pcc@google.com> In-Reply-To: <20210910211356.3603758-1-pcc@google.com> From: Andrey Konovalov Date: Fri, 10 Sep 2021 23:17:38 +0200 Message-ID: Subject: Re: [PATCH v2] kasan: test: add memcpy test that avoids out-of-bounds write To: Peter Collingbourne Cc: Robin Murphy , Will Deacon , Catalin Marinas , Marco Elver , Mark Rutland , Evgenii Stepanov , Alexander Potapenko , Linux ARM , Linux Memory Management List Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: b4pmuyakmyd1omwyx7orbzy6gwcyhaam Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=ljNKLE+C; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf03.hostedemail.com: domain of andreyknvl@gmail.com designates 209.85.166.46 as permitted sender) smtp.mailfrom=andreyknvl@gmail.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C117E3000099 X-HE-Tag: 1631308669-678217 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 10, 2021 at 11:14 PM Peter Collingbourne wrote: > > With HW tag-based KASAN, error checks are performed implicitly by the > load and store instructions in the memcpy implementation. A failed check > results in tag checks being disabled and execution will keep going. As a > result, under HW tag-based KASAN, prior to commit 1b0668be62cf ("kasan: > test: disable kmalloc_memmove_invalid_size for HW_TAGS"), this memcpy > would end up corrupting memory until it hits an inaccessible page and > causes a kernel panic. > > This is a pre-existing issue that was revealed by commit 285133040e6c > ("arm64: Import latest memcpy()/memmove() implementation") which changed > the memcpy implementation from using signed comparisons (incorrectly, > resulting in the memcpy being terminated early for negative sizes) > to using unsigned comparisons. > > It is unclear how this could be handled by memcpy itself in a reasonable > way. One possibility would be to add an exception handler that would force > memcpy to return if a tag check fault is detected -- this would make the > behavior roughly similar to generic and SW tag-based KASAN. However, > this wouldn't solve the problem for asynchronous mode and also makes > memcpy behavior inconsistent with manually copying data. > > This test was added as a part of a series that taught KASAN to detect > negative sizes in memory operations, see commit 8cceeff48f23 ("kasan: > detect negative size in memory operation function"). Therefore we > should keep testing for negative sizes with generic and SW tag-based > KASAN. But there is some value in testing small memcpy overflows, so > let's add another test with memcpy that does not destabilize the kernel > by performing out-of-bounds writes, and run it in all modes. > > Link: https://linux-review.googlesource.com/id/I048d1e6a9aff766c4a53f989fb0c83de68923882 > Signed-off-by: Peter Collingbourne > --- > lib/test_kasan.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/lib/test_kasan.c b/lib/test_kasan.c > index 8835e0784578..aa8e42250219 100644 > --- a/lib/test_kasan.c > +++ b/lib/test_kasan.c > @@ -493,7 +493,7 @@ static void kmalloc_oob_in_memset(struct kunit *test) > kfree(ptr); > } > > -static void kmalloc_memmove_invalid_size(struct kunit *test) > +static void kmalloc_memmove_negative_size(struct kunit *test) > { > char *ptr; > size_t size = 64; > @@ -515,6 +515,21 @@ static void kmalloc_memmove_invalid_size(struct kunit *test) > kfree(ptr); > } > > +static void kmalloc_memmove_invalid_size(struct kunit *test) > +{ > + char *ptr; > + size_t size = 64; > + volatile size_t invalid_size = size; > + > + ptr = kmalloc(size, GFP_KERNEL); > + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > + > + memset((char *)ptr, 0, 64); > + KUNIT_EXPECT_KASAN_FAIL(test, > + memmove((char *)ptr, (char *)ptr + 4, invalid_size)); > + kfree(ptr); > +} > + > static void kmalloc_uaf(struct kunit *test) > { > char *ptr; > @@ -1129,6 +1144,7 @@ static struct kunit_case kasan_kunit_test_cases[] = { > KUNIT_CASE(kmalloc_oob_memset_4), > KUNIT_CASE(kmalloc_oob_memset_8), > KUNIT_CASE(kmalloc_oob_memset_16), > + KUNIT_CASE(kmalloc_memmove_negative_size), > KUNIT_CASE(kmalloc_memmove_invalid_size), > KUNIT_CASE(kmalloc_uaf), > KUNIT_CASE(kmalloc_uaf_memset), > -- > 2.33.0.309.g3052b89438-goog > Reviewed-by: Andrey Konovalov Thanks!