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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE979C433EF for ; Tue, 29 Mar 2022 12:43:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234527AbiC2Moj (ORCPT ); Tue, 29 Mar 2022 08:44:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236499AbiC2MnX (ORCPT ); Tue, 29 Mar 2022 08:43:23 -0400 Received: from mail-ej1-x64a.google.com (mail-ej1-x64a.google.com [IPv6:2a00:1450:4864:20::64a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3A07229C9E for ; Tue, 29 Mar 2022 05:41:27 -0700 (PDT) Received: by mail-ej1-x64a.google.com with SMTP id ga31-20020a1709070c1f00b006cec400422fso8111732ejc.22 for ; Tue, 29 Mar 2022 05:41:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=uZfE98ax1//CK0YNbt0DpMbtwkdW56rBwmCC8QtRUVQ=; b=rze2RjOlA/9+bEmOt3GgL06iHO9tVctaBkBSNuYthH10DOkJoKc11FE48K74+k0ivC Y0nWiNQ4G1OYqS8rf/bOrZUnKPL4+s3Qg8Otbm5Qlrkc06XPathZWsOTt7qxe2+1gGu5 FQenUx3Cf6aNrVRr+SdeQSwMQ5LzNFQJT8QbStroSWij6LrjHD/nihi+tJAX5W+RJUrr HxLXz3xj47nfDdtYPis5g1jTn7KD+ivWymw+OHkntILtKy17lMhGhOuhUrTAddrGgeSQ 8yAh5HjKFp4PVxBIxkWGlL+Kip5Ab0jkaFPz+ndh/En9oJK7jpmUZwOcf0YBR3XglVyQ wshg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=uZfE98ax1//CK0YNbt0DpMbtwkdW56rBwmCC8QtRUVQ=; b=NlInswRov4pFmxbqMKd1AvSRKd7yDjIDfyY/4OvzirryUfz4MznEsVkncWJzIhWITn H/nTGXHCJ7XfH/B2PeUYsmPEcEFS74sPDOoSZBZ6gfDvL67+8ZSb3rXDmaLQGSN3cwj2 ipvL+yF8kj00v6tlbxVIVsRPZk8G98V2EZfz4nwsqhfLDAZXz3pLfkZsbSFpDi8m5coo 6YAM7JxWs6XZRJzmXBkLH5q7pxqmoOZ/+YFMBt+21nqyi/wowqBj4SXVJNmotOS5fb05 QpXWIhjhnJ9N2ck4jTosjbB4w2pFVlJBS9ZMD60yPCt7jXdGxB0Zu5zBvAXEIN8AoEA6 bBPA== X-Gm-Message-State: AOAM532B64svA8DyLREQE/Wp/UZbgGYoUO8D2OVw5wIoxqpP4vF1XmsS H+31GlaI4JZkRlwBDq7UBtMmyqXdUmI= X-Google-Smtp-Source: ABdhPJzxZmXUGeX7ZhTgf8n/xUXjeDK/oOkNktPicPG81/7+K/3c1esguj6n+m5UzDsEoEAM1ZAmk0LXhJs= X-Received: from glider.muc.corp.google.com ([2a00:79e0:15:13:36eb:759:798f:98c3]) (user=glider job=sendgmr) by 2002:a05:6402:657:b0:418:d875:bf12 with SMTP id u23-20020a056402065700b00418d875bf12mr4238058edx.89.1648557686159; Tue, 29 Mar 2022 05:41:26 -0700 (PDT) Date: Tue, 29 Mar 2022 14:39:50 +0200 In-Reply-To: <20220329124017.737571-1-glider@google.com> Message-Id: <20220329124017.737571-22-glider@google.com> Mime-Version: 1.0 References: <20220329124017.737571-1-glider@google.com> X-Mailer: git-send-email 2.35.1.1021.g381101b075-goog Subject: [PATCH v2 21/48] instrumented.h: add KMSAN support From: Alexander Potapenko To: glider@google.com Cc: Alexander Viro , 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 , Marco Elver , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- v2: -- move implementation of kmsan_copy_to_user() here Link: https://linux-review.googlesource.com/id/I43e93b9c02709e6be8d222342f1b044ac8bdbaaf --- include/linux/instrumented.h | 5 ++++- include/linux/kmsan-checks.h | 19 ++++++++++++++++++ mm/kmsan/hooks.c | 38 ++++++++++++++++++++++++++++++++++++ 3 files changed, 61 insertions(+), 1 deletion(-) diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h index ee8f7d17d34f5..c73c1b19e9227 100644 --- a/include/linux/instrumented.h +++ b/include/linux/instrumented.h @@ -2,7 +2,7 @@ /* * This header provides generic wrappers for memory access instrumentation that - * the compiler cannot emit for: KASAN, KCSAN. + * the compiler cannot emit for: KASAN, KCSAN, KMSAN. */ #ifndef _LINUX_INSTRUMENTED_H #define _LINUX_INSTRUMENTED_H @@ -10,6 +10,7 @@ #include #include #include +#include #include /** @@ -117,6 +118,7 @@ instrument_copy_to_user(void __user *to, const void *from, unsigned long n) { kasan_check_read(from, n); kcsan_check_read(from, n); + kmsan_copy_to_user(to, from, n, 0); } /** @@ -151,6 +153,7 @@ static __always_inline void instrument_copy_from_user_after(const void *to, const void __user *from, unsigned long n, unsigned long left) { + kmsan_unpoison_memory(to, n - left); } #endif /* _LINUX_INSTRUMENTED_H */ diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h index ecd8336190fc0..aabaf1ba7c251 100644 --- a/include/linux/kmsan-checks.h +++ b/include/linux/kmsan-checks.h @@ -84,6 +84,21 @@ void kmsan_unpoison_memory(const void *address, size_t size); */ void kmsan_check_memory(const void *address, size_t size); +/** + * kmsan_copy_to_user() - Notify KMSAN about a data transfer to userspace. + * @to: destination address in the userspace. + * @from: source address in the kernel. + * @to_copy: number of bytes to copy. + * @left: number of bytes not copied. + * + * If this is a real userspace data transfer, KMSAN checks the bytes that were + * actually copied to ensure there was no information leak. If @to belongs to + * the kernel space (which is possible for compat syscalls), KMSAN just copies + * the metadata. + */ +void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy, + size_t left); + #else #define kmsan_init(value) (value) @@ -98,6 +113,10 @@ static inline void kmsan_unpoison_memory(const void *address, size_t size) static inline void kmsan_check_memory(const void *address, size_t size) { } +static inline void kmsan_copy_to_user(void __user *to, const void *from, + size_t to_copy, size_t left) +{ +} #endif diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c index a13e15ef2bfd5..365eedcb08953 100644 --- 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_copy, + 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 unknown. + */ + + /* 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 <= left) + return; + + ua_flags = user_access_save(); + if ((u64)to < TASK_SIZE) { + /* This is a user memory access, check it. */ + kmsan_internal_check_memory((void *)from, to_copy - left, to, + REASON_COPY_TO_USER); + user_access_restore(ua_flags); + return; + } + /* Otherwise this is a kernel memory access. This happens when a compat + * syscall passes an argument allocated on the kernel stack to a real + * syscall. + * Don't check anything, just copy the shadow of the copied bytes. + */ + kmsan_internal_memmove_metadata((void *)to, (void *)from, + to_copy - left); + user_access_restore(ua_flags); +} +EXPORT_SYMBOL(kmsan_copy_to_user); + /* Functions from kmsan-checks.h follow. */ void kmsan_poison_memory(const void *address, size_t size, gfp_t flags) { -- 2.35.1.1021.g381101b075-goog