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 61F6CECAAA1 for ; Thu, 15 Sep 2022 15:08:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230421AbiIOPIL (ORCPT ); Thu, 15 Sep 2022 11:08:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49956 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230455AbiIOPG2 (ORCPT ); Thu, 15 Sep 2022 11:06:28 -0400 Received: from mail-ed1-x549.google.com (mail-ed1-x549.google.com [IPv6:2a00:1450:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6474222292 for ; Thu, 15 Sep 2022 08:05:29 -0700 (PDT) Received: by mail-ed1-x549.google.com with SMTP id t13-20020a056402524d00b00452c6289448so3775144edd.17 for ; Thu, 15 Sep 2022 08:05:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date; bh=78o9fcmZe1rakLyEcoaxPY9Q3UwZCgWFE2+savdbFCc=; b=rks9uNCmfYS/YqkY6U0g2qKgsPbMgCzE5to9YTQsDSGno7MLZ57OiRem/Dm1MXM0oH 61AdLXN3KgyZyk6WUXmAHXD8aHWhS7pncFYrPm6r8+mhpSEOBaFzKjhqrmkb5ObvQynG 3lyTmZNVq6qgxAzIWXhy+CSuzx0NPccWxOoEtJhpsVgel0Vw7Mfxk4UkKlJwhEMEQ0Fi 2tZcO8IrdExLJ33Ih9HNh0SgckWNA8DiGItv4ZovRLvY24k9gTbd/QACNW+CdrW7i0mE 8QR49AgHjVh9EsKUHDRNITyvpL24ACDRbhDaHoQexo2bF7giUI71j4WmqaXoSvQd5FNX krfA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date; bh=78o9fcmZe1rakLyEcoaxPY9Q3UwZCgWFE2+savdbFCc=; b=CjRHlVRYbXs3Fw0FN4TzNpMkRFnD3JuSYwGLsqsjeKEvhVewexOCX8ooDHShvSdvF5 7EImLrl1lLrkPElM0dk303pjAKFm/5O9cg70+BukJijU6eDdqm9uvj5/7NBLnWYUd++C 1bKXlnbA8pjpge+iNPWlOSYT2f6kEUOmiVJXhh0xFcl2ifE8In0CKcT+GjOE4UcPMLUV IHnP4McX4U++dSXJaEHJYkLrKflfSMIyexsrz2NpIQLDJA9XmTlFA9P6SGkRsSnR2rav S+MVLkIMPV22qfaVZGyak1gzmX4j99Fp0pnOWTsouss0ThEOiTCRjzV2onWqqY9FmnUg 6FLQ== X-Gm-Message-State: ACrzQf0jCFLmBBj73vCaOUBMdpxqzSbeOLcBFyUWs+BMvwIS3DIUhMSp U7w/4Ema2shQUywoVgd/V7/D7VXtEYs= X-Google-Smtp-Source: AMsMyM7StdmW2s0JDvShx0DM9h1H+6w0xzDkuDWLDHWgfE3mb+SwKv151I2wlKdpfNQSqM2uNm3YpsTkNJU= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:686d:27b5:495:85b7]) (user=glider job=sendgmr) by 2002:aa7:d8ce:0:b0:44e:8895:89c2 with SMTP id k14-20020aa7d8ce000000b0044e889589c2mr272708eds.382.1663254327816; Thu, 15 Sep 2022 08:05:27 -0700 (PDT) Date: Thu, 15 Sep 2022 17:03:52 +0200 In-Reply-To: <20220915150417.722975-1-glider@google.com> Mime-Version: 1.0 References: <20220915150417.722975-1-glider@google.com> X-Mailer: git-send-email 2.37.2.789.g6183377224-goog Message-ID: <20220915150417.722975-19-glider@google.com> Subject: [PATCH v7 18/43] instrumented.h: add KMSAN support From: Alexander Potapenko To: glider@google.com Cc: Alexander Viro , Alexei Starovoitov , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Biggers , 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 , Stephen Rothwell , 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-arch@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 Reviewed-by: Marco Elver --- v2: -- move implementation of kmsan_copy_to_user() here v5: -- simplify kmsan_copy_to_user() -- provide instrument_get_user() and instrument_put_user() v6: -- rebase after changing "x86: asm: instrument usercopy in get_user() and put_user()" Link: https://linux-review.googlesource.com/id/I43e93b9c02709e6be8d222342f1b044ac8bdbaaf --- include/linux/instrumented.h | 18 ++++++++++++----- include/linux/kmsan-checks.h | 19 ++++++++++++++++++ mm/kmsan/hooks.c | 38 ++++++++++++++++++++++++++++++++++++ 3 files changed, 70 insertions(+), 5 deletions(-) diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h index 9f1dba8f717b0..501fa84867494 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); } /** @@ -162,10 +165,14 @@ instrument_copy_from_user_after(const void *to, const void __user *from, * * @to destination variable, may not be address-taken */ -#define instrument_get_user(to) \ -({ \ +#define instrument_get_user(to) \ +({ \ + u64 __tmp = (u64)(to); \ + kmsan_unpoison_memory(&__tmp, sizeof(__tmp)); \ + to = __tmp; \ }) + /** * instrument_put_user() - add instrumentation to put_user()-like macros * @@ -177,8 +184,9 @@ instrument_copy_from_user_after(const void *to, const void __user *from, * @ptr userspace pointer to copy to * @size number of bytes to copy */ -#define instrument_put_user(from, ptr, size) \ -({ \ +#define instrument_put_user(from, ptr, size) \ +({ \ + kmsan_copy_to_user(ptr, &from, sizeof(from), 0); \ }) #endif /* _LINUX_INSTRUMENTED_H */ diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h index a6522a0c28df9..c4cae333deec5 100644 --- a/include/linux/kmsan-checks.h +++ b/include/linux/kmsan-checks.h @@ -46,6 +46,21 @@ 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 static inline void kmsan_poison_memory(const void *address, size_t size, @@ -58,6 +73,10 @@ 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 6f3e64b0b61f8..5c0eb25d984d7 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -205,6 +205,44 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end) kmsan_leave_runtime(); } +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); + } else { + /* 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) { -- 2.37.2.789.g6183377224-goog