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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA46EC3A5AC for ; Wed, 4 Sep 2019 21:00:24 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 898862087E for ; Wed, 4 Sep 2019 21:00:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="cAYy0GRP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 898862087E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=xTowf/UbpBdSuoIyhJUMGVdjU2eOAR9u+Yl9LzsuYFY=; b=cAYy0GRPgFAbw0 /UBcBY147ZtSTrXBA+a3hSspbVrIeCq4P1rwul0/TNV3vrH5J0ek/6uPUVMiqy5Cawf606yIBar5b ibBr1ZPHud/GF+D//cuY+nGB/H/7b6n5Zks975zm4i6qRozdswxtn6Tyk0FI9ObnNPtBhQphHyqB/ esjDjU02fWLEu7zgXWlLGI7MPyL0RtboH5rYFkphB85YxGw/D6qsaUK15uj4xMaHC5tCy8PxPDlqn rS3NoacR5yGUXXmXHqL9VkbUxqJ7MJqjb+kdyUdu7mUWpuf6EgMUhFtsK5tUlA6DMNGYKtGTESGeC CHZ4gwbKgJH9aZRuXZwQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i5cO3-0002IT-77; Wed, 04 Sep 2019 21:00:19 +0000 Received: from [2601:1c0:6200:6e8::e2a8] by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1i5cNx-0002I3-HN; Wed, 04 Sep 2019 21:00:13 +0000 Subject: Re: [PATCH v12 01/12] lib: introduce copy_struct_{to,from}_user helpers To: Aleksa Sarai , Al Viro , Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Ingo Molnar , Peter Zijlstra , Christian Brauner References: <20190904201933.10736-1-cyphar@cyphar.com> <20190904201933.10736-2-cyphar@cyphar.com> From: Randy Dunlap Message-ID: <949531fe-76d0-a8c2-77d7-5bf2444e8eb6@infradead.org> Date: Wed, 4 Sep 2019 14:00:11 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190904201933.10736-2-cyphar@cyphar.com> Content-Language: en-US X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Alexander Shishkin , Rasmus Villemoes , Alexei Starovoitov , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Jiri Olsa , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Tycho Andersen , Aleksa Sarai , linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linuxppc-dev@lists.ozlabs.org, linux-m68k@lists.linux-m68k.org, Andy Lutomirski , Namhyung Kim , David Drysdale , linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, linux-api@vger.kernel.org, Chanho Min , Oleg Nesterov , Eric Biederman , linux-alpha@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Linus Torvalds , containers@lists.linux-foundation.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, just kernel-doc fixes: On 9/4/19 1:19 PM, Aleksa Sarai wrote: > > diff --git a/lib/struct_user.c b/lib/struct_user.c > new file mode 100644 > index 000000000000..7301ab1bbe98 > --- /dev/null > +++ b/lib/struct_user.c > @@ -0,0 +1,182 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Copyright (C) 2019 SUSE LLC > + * Copyright (C) 2019 Aleksa Sarai > + */ > + > +#include > +#include > +#include > +#include > +#include > + > +#define BUFFER_SIZE 64 > + > + > +/** > + * copy_struct_to_user: copy a struct to user space use correct format: * copy_struct_to_user - copy a struct to user space > + * @dst: Destination address, in user space. > + * @usize: Size of @dst struct. > + * @src: Source address, in kernel space. > + * @ksize: Size of @src struct. > + * > + * Copies a struct from kernel space to user space, in a way that guarantees > + * backwards-compatibility for struct syscall arguments (as long as future > + * struct extensions are made such that all new fields are *appended* to the > + * old struct, and zeroed-out new fields have the same meaning as the old > + * struct). > + * > + * @ksize is just sizeof(*dst), and @usize should've been passed by user space. > + * The recommended usage is something like the following: > + * > + * SYSCALL_DEFINE2(foobar, struct foo __user *, uarg, size_t, usize) > + * { > + * int err; > + * struct foo karg = {}; > + * > + * // do something with karg > + * > + * err = copy_struct_to_user(uarg, usize, &karg, sizeof(karg)); > + * if (err) > + * return err; > + * > + * // ... > + * } > + * > + * There are three cases to consider: > + * * If @usize == @ksize, then it's copied verbatim. > + * * If @usize < @ksize, then kernel space is "returning" a newer struct to an > + * older user space. In order to avoid user space getting incomplete > + * information (new fields might be important), all trailing bytes in @src > + * (@ksize - @usize) must be zerored, otherwise -EFBIG is returned. > + * * If @usize > @ksize, then the kernel is "returning" an older struct to a > + * newer user space. The trailing bytes in @dst (@usize - @ksize) will be > + * zero-filled. > + * > + * Returns (in all cases, some data may have been copied): > + * * -EFBIG: (@usize < @ksize) and there are non-zero trailing bytes in @src. > + * * -EFAULT: access to user space failed. > + */ > +int copy_struct_to_user(void __user *dst, size_t usize, > + const void *src, size_t ksize) > +{ > + size_t size = min(ksize, usize); > + size_t rest = abs(ksize - usize); > + > + if (unlikely(usize > PAGE_SIZE)) > + return -EFAULT; > + if (unlikely(!access_ok(dst, usize))) > + return -EFAULT; > + > + /* Deal with trailing bytes. */ > + if (usize < ksize) { > + if (memchr_inv(src + size, 0, rest)) > + return -EFBIG; > + } else if (usize > ksize) { > + if (__memzero_user(dst + size, rest)) > + return -EFAULT; > + } > + /* Copy the interoperable parts of the struct. */ > + if (__copy_to_user(dst, src, size)) > + return -EFAULT; > + return 0; > +} > +EXPORT_SYMBOL(copy_struct_to_user); > + > +/** same here: > + * copy_struct_from_user: copy a struct from user space * copy_struct_from_user - copy a struct from user space > + * @dst: Destination address, in kernel space. This buffer must be @ksize > + * bytes long. > + * @ksize: Size of @dst struct. > + * @src: Source address, in user space. > + * @usize: (Alleged) size of @src struct. > + * > + * Copies a struct from user space to kernel space, in a way that guarantees > + * backwards-compatibility for struct syscall arguments (as long as future > + * struct extensions are made such that all new fields are *appended* to the > + * old struct, and zeroed-out new fields have the same meaning as the old > + * struct). > + * > + * @ksize is just sizeof(*dst), and @usize should've been passed by user space. > + * The recommended usage is something like the following: > + * > + * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize) > + * { > + * int err; > + * struct foo karg = {}; > + * > + * err = copy_struct_from_user(&karg, sizeof(karg), uarg, size); > + * if (err) > + * return err; > + * > + * // ... > + * } > + * > + * There are three cases to consider: > + * * If @usize == @ksize, then it's copied verbatim. > + * * If @usize < @ksize, then the user space has passed an old struct to a > + * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize) > + * are to be zero-filled. > + * * If @usize > @ksize, then the user space has passed a new struct to an > + * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize) > + * are checked to ensure they are zeroed, otherwise -E2BIG is returned. > + * > + * Returns (in all cases, some data may have been copied): > + * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src. > + * * -E2BIG: @usize is "too big" (at time of writing, >PAGE_SIZE). > + * * -EFAULT: access to user space failed. > + */ > +int copy_struct_from_user(void *dst, size_t ksize, > + const void __user *src, size_t usize) > +{ > + size_t size = min(ksize, usize); > + size_t rest = abs(ksize - usize); > + > + if (unlikely(usize > PAGE_SIZE)) > + return -EFAULT; > + if (unlikely(!access_ok(src, usize))) > + return -EFAULT; > + > + /* Deal with trailing bytes. */ > + if (usize < ksize) > + memset(dst + size, 0, rest); > + else if (usize > ksize) { > + const void __user *addr = src + size; > + char buffer[BUFFER_SIZE] = {}; > + > + while (rest > 0) { > + size_t bufsize = min(rest, sizeof(buffer)); > + > + if (__copy_from_user(buffer, addr, bufsize)) > + return -EFAULT; > + if (memchr_inv(buffer, 0, bufsize)) > + return -E2BIG; > + > + addr += bufsize; > + rest -= bufsize; > + } > + } > + /* Copy the interoperable parts of the struct. */ > + if (__copy_from_user(dst, src, size)) > + return -EFAULT; > + return 0; > +} > +EXPORT_SYMBOL(copy_struct_from_user); > thanks. -- ~Randy _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel