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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27D3BC19F28 for ; Wed, 3 Aug 2022 11:18:34 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 808856B0071; Wed, 3 Aug 2022 07:18:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7B8CC6B0072; Wed, 3 Aug 2022 07:18:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 680828E0001; Wed, 3 Aug 2022 07:18:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 57DE46B0071 for ; Wed, 3 Aug 2022 07:18:33 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 21E981C6E67 for ; Wed, 3 Aug 2022 11:18:33 +0000 (UTC) X-FDA: 79758033306.02.1B7BC02 Received: from mail-yb1-f182.google.com (mail-yb1-f182.google.com [209.85.219.182]) by imf19.hostedemail.com (Postfix) with ESMTP id C8A561A00F3 for ; Wed, 3 Aug 2022 11:18:32 +0000 (UTC) Received: by mail-yb1-f182.google.com with SMTP id n8so27892501yba.2 for ; Wed, 03 Aug 2022 04:18:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc; bh=PSBSqSCCzFolep6UPGhOMMv5cemuy3j+hc8VPw5MalM=; b=bMHRKq5scJSaAAH/R+bIAKiVW2q76rsyS5fqChaK2vvP0e6X8lMOJ9fvJpVbuVUJf9 IChi94VhhfBbdTI2M0D6R0ol52pbvpIWTX5RokondoQu4TASVcmEbumPPXkQwXm+8vUR loGd4D/ublp4BotEl4FDKW/8SbxfxgSBIcvBxNCqYCDJTWv1q9v//8OX1NtoVTjBQugp FRidMBKH+pYAfWV2DljliF14OLvHW8MohTIvNFWjXrqkVqpwGM8wo1GWYVY+fqTe2ZAK XtV8W+6uyL7Ih8Wr0y2ekD6szJA6VlkiENUbAtY64eghDk0gKJXZmOPEvPk/VMtM+HPV cqFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc; bh=PSBSqSCCzFolep6UPGhOMMv5cemuy3j+hc8VPw5MalM=; b=3yy464yZhKJV/h8S+kkE8lIUrh70ZEQwu7+wu7WPK0Dii10GYhQFlXSInvpDnJ4ypH 6qJHu3ymkMPtNc1TBfQ2zoC3kQJgX6aMmqkCHdnUtQn85nh013kWQi3YS0p3DnQNoL5o dHG+wpQwZoqFWwh/NvjyudsPgd6KyiUiAHti5XmxsYe9//LiO5c7XolBCB+ip1UMs0+x EJO3VQUvxMowicqlScCFF9VupxEyE6fR1GlTsn26Yv09vupKHq1lBLnLd45x0682/vgh 8PCbOtjzNVcIZErRG3u2BwIxttgDRHsR4Lj+hyPZz9kEKaRQjyzKwqP6x55NE1WZNTCr R5gA== X-Gm-Message-State: ACgBeo07HZPgzlC5me9LZrZ86ftCSw/RXET/35Cbd6s7HHiSCpViMnKr zEIKZS3owfLXH54bsD9M1Lz4q5++Wf63QYT2VblkWw== X-Google-Smtp-Source: AA6agR7nzADdbpq41G4xAhK/5KipIY2zuod2SPum8O77h1V58WRcrWLdk3ucV/uv9E8f8txAcMtuwxqzwLK38mf09ss= X-Received: by 2002:a25:1687:0:b0:671:8241:610d with SMTP id 129-20020a251687000000b006718241610dmr19350594ybw.250.1659525511896; Wed, 03 Aug 2022 04:18:31 -0700 (PDT) MIME-Version: 1.0 References: <20220701142310.2188015-1-glider@google.com> <20220701142310.2188015-19-glider@google.com> In-Reply-To: From: Alexander Potapenko Date: Wed, 3 Aug 2022 13:17:55 +0200 Message-ID: Subject: Re: [PATCH v4 18/45] instrumented.h: add KMSAN support To: Marco Elver Cc: Alexander Viro , Alexei Starovoitov , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev , Linux Memory Management List , Linux-Arch , LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1659525512; a=rsa-sha256; cv=none; b=Wv2t9B5JS80Kv2OkrdHDMAhW6HXO6JucObwtVQqn/2gQfPWLl6PjEC3UO/wnoQ6t5IGtmx qEIXrRhaBKAF+8DsVijlKKuHmEEbeNuyF6m3zQNCRELd3QhDF+TLvYlD50HS/eq2FevAQf rM9YWvLsaAmGpKXvGdxo9NAaaHLoZvY= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=bMHRKq5s; spf=pass (imf19.hostedemail.com: domain of glider@google.com designates 209.85.219.182 as permitted sender) smtp.mailfrom=glider@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1659525512; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=PSBSqSCCzFolep6UPGhOMMv5cemuy3j+hc8VPw5MalM=; b=Idxm7gg62W47woF1nuSLiI+jWtmYQpdtq1HEpxamdFQ97gv035mK+QRM6Bwc6PH5fAJDBP KaOeG4uSlS7PKvM6L28jslZYGXvQDlBxaeZp7QmMnRMJcJzL2VZtor3f7d1KL340OoGAR3 90HKWznbQlqkF0DwRxa4ejzp62skJdQ= X-Rspam-User: X-Stat-Signature: hsz7ff9xegfo67gnq1qbpwcm1jxthrt7 X-Rspamd-Queue-Id: C8A561A00F3 Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=bMHRKq5s; spf=pass (imf19.hostedemail.com: domain of glider@google.com designates 209.85.219.182 as permitted sender) smtp.mailfrom=glider@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam02 X-HE-Tag: 1659525512-146933 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 Tue, Jul 12, 2022 at 3:52 PM Marco Elver wrote: > > On Fri, 1 Jul 2022 at 16:24, Alexander Potapenko wrot= e: > > > > To avoid false positives, KMSAN needs to unpoison the data copied from > > the userspace. To detect infoleaks - check the memory buffer passed to > > copy_to_user(). > > > > Signed-off-by: Alexander Potapenko > > Reviewed-by: Marco Elver > > With the code simplification below. > > [...] > > --- a/mm/kmsan/hooks.c > > +++ b/mm/kmsan/hooks.c > > @@ -212,6 +212,44 @@ void kmsan_iounmap_page_range(unsigned long start,= unsigned long end) > > } > > EXPORT_SYMBOL(kmsan_iounmap_page_range); > > > > +void kmsan_copy_to_user(void __user *to, const void *from, size_t to_c= opy, > > + size_t left) > > +{ > > + unsigned long ua_flags; > > + > > + if (!kmsan_enabled || kmsan_in_runtime()) > > + return; > > + /* > > + * At this point we've copied the memory already. It's hard to = check it > > + * before copying, as the size of actually copied buffer is unk= nown. > > + */ > > + > > + /* copy_to_user() may copy zero bytes. No need to check. */ > > + if (!to_copy) > > + return; > > + /* Or maybe copy_to_user() failed to copy anything. */ > > + if (to_copy <=3D left) > > + return; > > + > > + ua_flags =3D user_access_save(); > > + if ((u64)to < TASK_SIZE) { > > + /* This is a user memory access, check it. */ > > + kmsan_internal_check_memory((void *)from, to_copy - lef= t, to, > > + REASON_COPY_TO_USER); > > This could just do "} else {" and the stuff below, and would result in > simpler code with no explicit "return" and no duplicated > user_access_restore(). Sounds good, will do. --=20 Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Stra=C3=9Fe, 33 80636 M=C3=BCnchen Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg