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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=ham 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 1EE27C43381 for ; Tue, 26 Feb 2019 15:14:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0A8521850 for ; Tue, 26 Feb 2019 15:14:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551194090; bh=FPrVNzBCZerPFnCY9ddfNYadDXEdihPnTn+QAoewdMo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:In-Reply-To: References:List-ID:From; b=Pwl7ieko7D1Kn5uyxPW9taxhs8R5o3a/g66tJNNqM/76pWoypMcIN+CDR2b8nQCpB meRhhurq1ahVWTafx0Z+dk2ewwt8w2+qf6GwU8S7kdAV4Utlx15vxKr3k9ZtgWE2lM K+vQB5Cqzi/TFUel/FrHmp/wWYCtSaHV6p+apYjA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727560AbfBZPOs (ORCPT ); Tue, 26 Feb 2019 10:14:48 -0500 Received: from mail.kernel.org ([198.145.29.99]:48854 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726222AbfBZPOs (ORCPT ); Tue, 26 Feb 2019 10:14:48 -0500 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 76D862184D; Tue, 26 Feb 2019 15:14:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551194086; bh=FPrVNzBCZerPFnCY9ddfNYadDXEdihPnTn+QAoewdMo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:In-Reply-To: References:From; b=reHtFMmP4btK7RHHFbPUBEWJg0+FE4zyfGFksd+c5o12PTSK9lkFYXkggbH+t7MI1 15hq/Tx6Ot1KKuz4O8tE1BXCyXXuLRNFJIyuRYUJrh10zOG/jNB0/PUea60qqn6TBb Jcc/cAWSImyBfFmm3JJ59ns2sSjacJP7TtxRN89I= From: Masami Hiramatsu To: Steven Rostedt , Linus Torvalds Cc: mhiramat@kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Ingo Molnar , Andrew Morton , Changbin Du , Jann Horn , Kees Cook , Andy Lutomirski , Alexei Starovoitov , Nadav Amit , Peter Zijlstra Subject: [RFC PATCH v2] uaccess: Add non-pagefault user-space read functions Date: Wed, 27 Feb 2019 00:14:22 +0900 Message-Id: <155119406184.22712.10132715741020219809.stgit@devbox> X-Mailer: git-send-email 2.13.6 In-Reply-To: <20190226212440.c59f0a3fd5a9133cf980e137@kernel.org> References: <20190226212440.c59f0a3fd5a9133cf980e137@kernel.org> In-Reply-To: <20190226212440.c59f0a3fd5a9133cf980e137@kernel.org> References: <20190226212440.c59f0a3fd5a9133cf980e137@kernel.org> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add probe_user_read() and strncpy_from_unsafe_user() which will not involves mm_sem so we can use it for accessing user-space in irq-handler. Signed-off-by: Masami Hiramatsu --- Changes in v2: - Simplify strncpy_from_unsafe_user() using strncpy_from_user() according to Linus's suggestion. - Simplify probe_user_read() not using intermediate function. --- include/linux/uaccess.h | 13 +++++++ mm/maccess.c | 91 ++++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 98 insertions(+), 6 deletions(-) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 37b226e8df13..906573b8f02c 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -240,6 +240,17 @@ extern long probe_kernel_read(void *dst, const void *src, size_t size); extern long __probe_kernel_read(void *dst, const void *src, size_t size); /* + * probe_user_read(): safely attempt to read from a location in user space + * @dst: pointer to the buffer that shall take the data + * @src: address to read from + * @size: size of the data chunk + * + * Safely read from address @src to the buffer at @dst. If a kernel fault + * happens, handle that and return -EFAULT. + */ +extern long probe_user_read(void *dst, const void __user *src, size_t size); + +/* * probe_kernel_write(): safely attempt to write to a location * @dst: address to write to * @src: pointer to the data that shall be written @@ -252,6 +263,8 @@ extern long notrace probe_kernel_write(void *dst, const void *src, size_t size); extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size); extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count); +extern long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr, + long count); /** * probe_kernel_address(): safely attempt to read from a location diff --git a/mm/maccess.c b/mm/maccess.c index ec00be51a24f..0209c9eeaa70 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -5,8 +5,20 @@ #include #include +static __always_inline long +probe_read_common(void *dst, const void __user *src, size_t size) +{ + long ret; + + pagefault_disable(); + ret = __copy_from_user_inatomic(dst, src, size); + pagefault_enable(); + + return ret ? -EFAULT : 0; +} + /** - * probe_kernel_read(): safely attempt to read from a location + * probe_kernel_read(): safely attempt to read from a kernel-space location * @dst: pointer to the buffer that shall take the data * @src: address to read from * @size: size of the data chunk @@ -29,17 +41,44 @@ long __probe_kernel_read(void *dst, const void *src, size_t size) mm_segment_t old_fs = get_fs(); set_fs(KERNEL_DS); - pagefault_disable(); - ret = __copy_from_user_inatomic(dst, - (__force const void __user *)src, size); - pagefault_enable(); + ret = probe_read_common(dst, (__force const void __user *)src, size); set_fs(old_fs); - return ret ? -EFAULT : 0; + return ret; } EXPORT_SYMBOL_GPL(probe_kernel_read); /** + * probe_user_read(): safely attempt to read from a user-space location + * @dst: pointer to the buffer that shall take the data + * @src: address to read from. This must be a user address. + * @size: size of the data chunk + * + * Safely read from user address @src to the buffer at @dst. If a kernel fault + * happens, handle that and return -EFAULT. + */ + +long __weak probe_user_read(void *dst, const void __user *src, size_t size) + __attribute__((alias("__probe_user_read"))); + +long __probe_user_read(void *dst, const void __user *src, size_t size) +{ + long ret; + mm_segment_t old_fs = get_fs(); + + set_fs(USER_DS); + + if (!access_ok(src, size)) + ret = -EFAULT; + else + ret = probe_read_common(dst, src, size); + + set_fs(old_fs); + return ret; +} +EXPORT_SYMBOL_GPL(probe_user_read); + +/** * probe_kernel_write(): safely attempt to write to a location * @dst: address to write to * @src: pointer to the data that shall be written @@ -66,6 +105,7 @@ long __probe_kernel_write(void *dst, const void *src, size_t size) } EXPORT_SYMBOL_GPL(probe_kernel_write); + /** * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address. * @dst: Destination address, in kernel space. This buffer must be at @@ -105,3 +145,42 @@ long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count) return ret ? -EFAULT : src - unsafe_addr; } + +/** + * strncpy_from_unsafe_user: - Copy a NUL terminated string from unsafe user + * address. + * @dst: Destination address, in kernel space. This buffer must be at + * least @count bytes long. + * @unsafe_addr: Unsafe user address. + * @count: Maximum number of bytes to copy, including the trailing NUL. + * + * Copies a NUL-terminated string from unsafe user address to kernel buffer. + * + * On success, returns the length of the string INCLUDING the trailing NUL. + * + * If access fails, returns -EFAULT (some data may have been copied + * and the trailing NUL added). + * + * If @count is smaller than the length of the string, copies @count-1 bytes, + * sets the last byte of @dst buffer to NUL and returns @count. + */ +long strncpy_from_unsafe_user(char *dst, const void __user *src, long count) +{ + mm_segment_t old_fs = get_fs(); + long ret; + + if (unlikely(count <= 0)) + return 0; + + set_fs(USER_DS); + pagefault_disable(); + ret = strncpy_from_user(dst, src, count); + pagefault_enable(); + set_fs(old_fs); + if (ret >= count) { + ret = count; + dst[ret - 1] = '\0'; + } else if (ret > 0) + ret++; + return ret; +}