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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 253CEC04EB9 for ; Mon, 3 Dec 2018 17:56:16 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 A8E8020848 for ; Mon, 3 Dec 2018 17:56:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A8E8020848 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 437t314M6ZzDqXX for ; Tue, 4 Dec 2018 04:56:13 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=rppt@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 437t0d0qKwzDqV6 for ; Tue, 4 Dec 2018 04:54:08 +1100 (AEDT) Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wB3HihNv007103 for ; Mon, 3 Dec 2018 12:54:06 -0500 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0a-001b2d01.pphosted.com with ESMTP id 2p58m22b1n-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 03 Dec 2018 12:54:06 -0500 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 3 Dec 2018 17:54:04 -0000 Received: from b06cxnps3074.portsmouth.uk.ibm.com (9.149.109.194) by e06smtp01.uk.ibm.com (192.168.101.131) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 3 Dec 2018 17:53:59 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wB3Hrwto49545460 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 3 Dec 2018 17:53:58 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4BF5DA4051; Mon, 3 Dec 2018 17:53:58 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5E0E2A4040; Mon, 3 Dec 2018 17:53:57 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.206.196]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 3 Dec 2018 17:53:57 +0000 (GMT) Date: Mon, 3 Dec 2018 19:53:55 +0200 From: Mike Rapoport To: Christophe Leroy Subject: Re: [PATCH 1/2] mm: add probe_user_read() and probe_user_address() References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 18120317-4275-0000-0000-000002EB6E06 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18120317-4276-0000-0000-000037F8729D Message-Id: <20181203175354.GE26700@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-12-03_09:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1812030164 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Paul Mackerras , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Dec 03, 2018 at 05:06:42PM +0000, Christophe Leroy wrote: > In the powerpc, there are several places implementing safe > access to user data. This is sometimes implemented using > probe_kernel_address() with additional access_ok() verification, > sometimes with get_user() enclosed in a pagefault_disable()/enable() > pair, etc... : > show_user_instructions() > bad_stack_expansion() > p9_hmi_special_emu() > fsl_pci_mcheck_exception() > read_user_stack_64() > read_user_stack_32() on PPC64 > read_user_stack_32() on PPC32 > power_pmu_bhrb_to() > > In the same spirit as probe_kernel_read() and probe_kernel_address(), > this patch adds probe_user_read() and probe_user_address(). > > probe_user_read() does the same as probe_kernel_read() but > first checks that it is really a user address. > > probe_user_address() is a shortcut to probe_user_read() > > Signed-off-by: Christophe Leroy > --- > Changes since RFC: Made a static inline function instead of weak function as recommended by Kees. > > include/linux/uaccess.h | 42 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h > index efe79c1cdd47..83ea8aefca75 100644 > --- a/include/linux/uaccess.h > +++ b/include/linux/uaccess.h > @@ -266,6 +266,48 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count); > #define probe_kernel_address(addr, retval) \ > probe_kernel_read(&retval, addr, sizeof(retval)) > > +/** > + * probe_user_read(): safely attempt to read from a user location > + * @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. > + * > + * We ensure that the copy_from_user is executed in atomic context so that > + * do_page_fault() doesn't attempt to take mmap_sem. This makes > + * probe_user_read() suitable for use within regions where the caller > + * already holds mmap_sem, or other locks which nest inside mmap_sem. Please add 'Returns:' description. > + */ > + > +#ifndef probe_user_read > +static __always_inline long probe_user_read(void *dst, const void __user *src, > + size_t size) > +{ > + long ret; > + > + if (!access_ok(VERIFY_READ, src, size)) > + return -EFAULT; > + > + pagefault_disable(); > + ret = __copy_from_user_inatomic(dst, src, size); > + pagefault_enable(); > + > + return ret ? -EFAULT : 0; > +} > +#endif > + > +/** > + * probe_user_address(): safely attempt to read from a user location > + * @addr: address to read from > + * @retval: read into this variable > + * > + * Returns 0 on success, or -EFAULT. This should be 'Return:' for kernel-doc to recognise it as return value description. > + */ > +#define probe_user_address(addr, retval) \ > + probe_user_read(&(retval), addr, sizeof(retval)) > + > #ifndef user_access_begin > #define user_access_begin() do { } while (0) > #define user_access_end() do { } while (0) > -- > 2.13.3 > -- Sincerely yours, Mike.