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 EE7E1C433EF for ; Tue, 26 Apr 2022 16:47:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353291AbiDZQu2 (ORCPT ); Tue, 26 Apr 2022 12:50:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353286AbiDZQtF (ORCPT ); Tue, 26 Apr 2022 12:49:05 -0400 Received: from mail-ej1-x649.google.com (mail-ej1-x649.google.com [IPv6:2a00:1450:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4BDD6EA6 for ; Tue, 26 Apr 2022 09:45:14 -0700 (PDT) Received: by mail-ej1-x649.google.com with SMTP id dp12-20020a170906c14c00b006e7e8234ae2so9350162ejc.2 for ; Tue, 26 Apr 2022 09:45:14 -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=PbBXRuKFLbtHp5AyM4yBRHn0ZnsWI8OdvT0jRFW7dGk=; b=UzHbOhn27qVpptDuuU81LcEBLt7rOLKE1Z4yNRMf0zkmHeofLcAdHL+SqDQLWH82Il 6cto3RZpExd7ZEnNnAe35UkzS2jkAjUX69Q2YDKqz0g6NCSq/WjRaGJHtw43EHu3cb2U 74H178/TCTR18+CzvmKyfFX9b2Z4X7YP6GK3JO9AiYQ2MlSw+zDsaJJUZQ1bJWeQtgsz KYwuUT517UeVfpvjEvnbP65ucrioTA1bLWKz7WGDz6RnAmYdszQ4/JzyWv4TAbKiuOGb sOlT+jbPA+6lfsFROSMY/3byYOL6djxZQq1uuRZWZI8XWXlEes7tAvr+I/ZTgHKJS0le Mwmg== 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=PbBXRuKFLbtHp5AyM4yBRHn0ZnsWI8OdvT0jRFW7dGk=; b=c+pi3sGdEIBz/PdFn5TQLDM6DsdhCG13tVegFw1XXRVz0qtiNja/eRea7klYAPwlc+ cgaYDBJqIAYVyKEsS532x5qGFlEn6hbwyMvtYOCDTE+gJZ9rxkp8H+Hh5raYbw/FnYY0 mI6WsH2/p66X85eU+yKjkRbhn6AwzSxp8QPSuniYLSKCHWJc4X6FwQflge4RN/rXTxQX m7IRaxiTX//3eV1SNDpGiAIM+KWNv93oMTpKNNFZraEx3QOAHuFVhwwi0anoNolk5kAZ d79aokVVcpafgUwOMlREg4l8dnwLWfADOdqKBphFISzvXAh7pQMml6v9k0tdkiJdwXwT j4Ew== X-Gm-Message-State: AOAM530RCFppeg0S0BM+Q8ELKtGsKoEyzk4bRgyWncFBQLTvqDNRVLoK xey8RGAk1ySZuwgSPGSwvfo0VKNMe3U= X-Google-Smtp-Source: ABdhPJxJswKGNx1XbX2+/B2Rkoy0KYZvI3ec74susirQuoLEq7dCT4VYCkV8muuT7Bszjk5rbONHKLbz8bs= X-Received: from glider.muc.corp.google.com ([2a00:79e0:15:13:d580:abeb:bf6d:5726]) (user=glider job=sendgmr) by 2002:a05:6402:400b:b0:425:f59a:c221 with SMTP id d11-20020a056402400b00b00425f59ac221mr7821838eda.307.1650991512487; Tue, 26 Apr 2022 09:45:12 -0700 (PDT) Date: Tue, 26 Apr 2022 18:42:49 +0200 In-Reply-To: <20220426164315.625149-1-glider@google.com> Message-Id: <20220426164315.625149-21-glider@google.com> Mime-Version: 1.0 References: <20220426164315.625149-1-glider@google.com> X-Mailer: git-send-email 2.36.0.rc2.479.g8af0fa9b8e-goog Subject: [PATCH v3 20/46] 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 , kasan-dev@googlegroups.com, 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 43a529569053d..1cdb4420977f1 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) { -- 2.36.0.rc2.479.g8af0fa9b8e-goog