From nobody Mon Apr 6 18:42:51 2026 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 59B9AECAAD3 for ; Mon, 5 Sep 2022 12:29:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237167AbiIEM3L (ORCPT ); Mon, 5 Sep 2022 08:29:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237485AbiIEM1r (ORCPT ); Mon, 5 Sep 2022 08:27:47 -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 49DE35F20F for ; Mon, 5 Sep 2022 05:25:49 -0700 (PDT) Received: by mail-ej1-x64a.google.com with SMTP id ho13-20020a1709070e8d00b00730a655e173so2265535ejc.8 for ; Mon, 05 Sep 2022 05:25:49 -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=AsRZmg4FcaRnkB2xKxGrm6iL2iDGcXmhS0tj+V1yFF2aDqOfpFXiHIRCT6zqVsW0aD N5h5Pb+5EyE1FTqgt8cLBFPdqtvKIDtXWqRbvYO/ATFWFWd2HAeTUbRSL9GKhNVVG3UR +Cz38urRZj9ZruT9hAA3LKKRoer80w2xrOai37ChA1Od6371h/dioMQgPIKGmaf+yNq2 ppD8ItTWVHSMEd1mMuPT2G7k7EIkowWAHt4nuZyfb6OsxakVTglc/JRDQZk9/I+LgGq5 2tgG5D4XNS/pj0QT5fzRb+TJYhHEDdcxlyJc0krsiHxzHfX0aka2JbETQ+vXADss1MTT Brbw== 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=ertnVrMeF3Ie8qgglF68J0PRgUvVb2T5248FSPjrnIjqyW2xdpx8RUgG/D8ZCky6EJ n0/WMR3xa78WE2Uxg4x8vWhKWRz5bytjJeNeyJuHqahh7s2z8JNNrgmtxS2s6cuvVEj6 S736pIn6vYjr8hTRy/UYWCdltzPx4IK53r+/HEcbwNtklW1lId6e0IYR5bmveDM5hjTj Q2t9cihEOmPO3RaxQXyA/bi/UHZIU4DzMDcsbfoFva3nXE5nLI9huL0g2uSXzsaY8Xyd rFxe80AxhIFxwTehXT6pASMT3+D+QVdncwKepI7bqabBAY16bLTOzuC27VGE2BZAFoJ/ FyAg== X-Gm-Message-State: ACgBeo0gVbxnvweUVuvrmaVIw9pt+bflPx/1br87X8n189nE1a8Xe6Ah PY45yhyTVTdiwffc6sQUCXNgdCBh0d4= X-Google-Smtp-Source: AA6agR6O+LsZ4k4byGii1HsmWG4VXEYNBtCLaymsFKv9VXP42ACoLM9ggDG8gs81G7Gmde8sHdwK3hc4QxA= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:b808:8d07:ab4a:554c]) (user=glider job=sendgmr) by 2002:a17:906:9bd9:b0:73d:da74:120c with SMTP id de25-20020a1709069bd900b0073dda74120cmr32752711ejc.412.1662380746896; Mon, 05 Sep 2022 05:25:46 -0700 (PDT) Date: Mon, 5 Sep 2022 14:24:26 +0200 In-Reply-To: <20220905122452.2258262-1-glider@google.com> Mime-Version: 1.0 References: <20220905122452.2258262-1-glider@google.com> X-Mailer: git-send-email 2.37.2.789.g6183377224-goog Message-ID: <20220905122452.2258262-19-glider@google.com> Subject: [PATCH v6 18/44] 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 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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/I43e93b9c02709e6be8d222342f1= b044ac8bdbaaf --- 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 @@ =20 /* * 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 =20 /** @@ -117,6 +118,7 @@ instrument_copy_to_user(void __user *to, const void *fr= om, unsigned long n) { kasan_check_read(from, n); kcsan_check_read(from, n); + kmsan_copy_to_user(to, from, n, 0); } =20 /** @@ -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); } =20 /** @@ -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 =3D (u64)(to); \ + kmsan_unpoison_memory(&__tmp, sizeof(__tmp)); \ + to =3D __tmp; \ }) =20 + /** * instrument_put_user() - add instrumentation to put_user()-like macros * @@ -177,8 +184,9 @@ instrument_copy_from_user_after(const void *to, const v= oid __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); \ }) =20 #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 s= ize); */ void kmsan_check_memory(const void *address, size_t size); =20 +/** + * 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 co= pies + * the metadata. + */ +void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy, + size_t left); + #else =20 static inline void kmsan_poison_memory(const void *address, size_t size, @@ -58,6 +73,10 @@ static inline void kmsan_unpoison_memory(const void *add= ress, 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) +{ +} =20 #endif =20 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, uns= igned long end) kmsan_leave_runtime(); } =20 +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 <=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 - 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) { --=20 2.37.2.789.g6183377224-goog