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,URIBL_BLOCKED,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 C1D87C04AA7 for ; Wed, 15 May 2019 05:38:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 88F102168B for ; Wed, 15 May 2019 05:38:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557898707; bh=rPf8rrfvUjmxPcg4eGhiC9rBuZlxs6VD6GxQu3Q+ULY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2MtDVUxLVNIL/VGqhZbB71veQ8EISYKdqKGS9B0LtRG3fGYNnW1OgniXZ8+lWauN9 vyC2JLdxmX1MobQIvtTRWRiOUqP+O239wBpGz4KeGfIi2hOSNXcOuA6dEc9RI/qB70 bhIz3ZT0krpxh+mOfio2PeRxsKlJH50jx5Uq/MhM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726510AbfEOFi0 (ORCPT ); Wed, 15 May 2019 01:38:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:52634 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725781AbfEOFi0 (ORCPT ); Wed, 15 May 2019 01:38:26 -0400 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 966592166E; Wed, 15 May 2019 05:38:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557898704; bh=rPf8rrfvUjmxPcg4eGhiC9rBuZlxs6VD6GxQu3Q+ULY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AVRMPJZ6MvTBSSgA7SaeyJrfDsD2FtXlNif5Ig7v3XRHLSNPcoPvJL/xduOHuWLtW Mx9uxHUDonOazHgdCIdutpwgS7185GTxnOZEvQoz+V0XV0QPlfY1moTmNs9+DRdC6T sKkxoCp3FPC1QCKAoCQ6AUbfskLII2I/ebiCQDxw= From: Masami Hiramatsu To: Steven Rostedt , Linus Torvalds , Shuah Khan , Arnaldo Carvalho de Melo , Peter Zijlstra 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 , Joel Fernandes , yhs@fb.com Subject: [PATCH -tip v9 2/6] uaccess: Add non-pagefault user-space read functions Date: Wed, 15 May 2019 14:38:18 +0900 Message-Id: <155789869802.26965.4940338412595759063.stgit@devnote2> X-Mailer: git-send-email 2.17.1 In-Reply-To: <155789866428.26965.8344923934342528416.stgit@devnote2> References: <155789866428.26965.8344923934342528416.stgit@devnote2> 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(), strncpy_from_unsafe_user() and strnlen_unsafe_user() which allows caller to access user-space in IRQ context. Current probe_kernel_read() and strncpy_from_unsafe() are not available for user-space memory, because it sets KERNEL_DS while accessing data. On some arch, user address space and kernel address space can be co-exist, but others can not. In that case, setting KERNEL_DS means given address is treated as a kernel address space. Also strnlen_user() is only available from user context since it can sleep if pagefault is enabled. To access user-space memory without pagefault, we need these new functions which sets USER_DS while accessing the data. Signed-off-by: Masami Hiramatsu Acked-by: Steven Rostedt (VMware) --- Changes in v8: - Fix style issues and typos according to Ingo's comment (Thanks!) Changes in v6: - Remove user_access_ok() Changes in v5: - Simplify probe_user_read() (Thanks, Peter!) - Add strnlen_unsafe_user() Changes in v3: - Use user_access_ok() for probe_user_read(). 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 | 14 +++++ mm/maccess.c | 122 +++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 130 insertions(+), 6 deletions(-) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 5a43ef7db492..9c435c3f2105 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -242,6 +242,17 @@ static inline unsigned long __copy_from_user_inatomic_nocache(void *to, 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 @@ -255,6 +266,9 @@ 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); +extern long strnlen_unsafe_user(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..19c8c3dc14df 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 @@ -29,16 +41,40 @@ 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 = -EFAULT; + mm_segment_t old_fs = get_fs(); + + set_fs(USER_DS); + if (access_ok(src, size)) + 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 @@ -66,6 +102,7 @@ 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 +142,76 @@ 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 *unsafe_addr, + 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, unsafe_addr, count); + pagefault_enable(); + set_fs(old_fs); + + if (ret >= count) { + ret = count; + dst[ret - 1] = '\0'; + } else if (ret > 0) { + ret++; + } + + return ret; +} + +/** + * strnlen_unsafe_user: - Get the size of a user string INCLUDING final NUL. + * @unsafe_addr: The string to measure. + * @count: Maximum count (including NUL) + * + * Get the size of a NUL-terminated string in user space without pagefault. + * + * Returns the size of the string INCLUDING the terminating NUL. + * + * If the string is too long, returns a number larger than @count. User + * has to check the return value against "> count". + * On exception (or invalid count), returns 0. + * + * Unlike strnlen_user, this can be used from IRQ handler etc. because + * it disables pagefaults. + */ +long strnlen_unsafe_user(const void __user *unsafe_addr, long count) +{ + mm_segment_t old_fs = get_fs(); + int ret; + + set_fs(USER_DS); + pagefault_disable(); + ret = strnlen_user(unsafe_addr, count); + pagefault_enable(); + set_fs(old_fs); + + return ret; +}