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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 31387C10F13 for ; Tue, 16 Apr 2019 12:09:47 +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 792EA205ED for ; Tue, 16 Apr 2019 12:09:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 792EA205ED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=de.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 44k41M6dN8zDqKs for ; Tue, 16 Apr 2019 22:09:43 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=de.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=schwidefsky@de.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=de.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 44k3zF5xxPzDq8X for ; Tue, 16 Apr 2019 22:07:52 +1000 (AEST) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3GC7HfB051927 for ; Tue, 16 Apr 2019 08:07:49 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2rwe3k1reu-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 16 Apr 2019 08:07:46 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 16 Apr 2019 13:07:01 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3GC70av52756532 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 16 Apr 2019 12:07:00 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1936EAE055; Tue, 16 Apr 2019 12:07:00 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C3789AE053; Tue, 16 Apr 2019 12:06:59 +0000 (GMT) Received: from mschwideX1 (unknown [9.152.212.60]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 16 Apr 2019 12:06:59 +0000 (GMT) Date: Tue, 16 Apr 2019 14:06:58 +0200 From: Martin Schwidefsky To: Linus Torvalds Subject: Re: Linux 5.1-rc5 In-Reply-To: <20190416110906.6c773aff@mschwideX1> References: <20190415051919.GA31481@infradead.org> <20190416110906.6c773aff@mschwideX1> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19041612-0008-0000-0000-000002DA661D X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19041612-0009-0000-0000-000022469E2E Message-Id: <20190416140658.2cb73a3f@mschwideX1> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-04-16_05:, , 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-1904160083 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: Christoph Hellwig , linuxppc-dev@lists.ozlabs.org, Linux List Kernel Mailing , linux-s390 Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, 16 Apr 2019 11:09:06 +0200 Martin Schwidefsky wrote: > On Mon, 15 Apr 2019 09:17:10 -0700 > Linus Torvalds wrote: > > > On Sun, Apr 14, 2019 at 10:19 PM Christoph Hellwig wrote: > > > > > > Can we please have the page refcount overflow fixes out on the list > > > for review, even if it is after the fact? > > > > They were actually on a list for review long before the fact, but it > > was the security mailing list. The issue actually got discussed back > > in January along with early versions of the patches, but then we > > dropped the ball because it just wasn't on anybody's radar and it got > > resurrected late March. Willy wrote a rather bigger patch-series, and > > review of that is what then resulted in those commits. So they may > > look recent, but that's just because the original patches got > > seriously edited down and rewritten. > > First time I hear about this, thanks for the heads up. > > > That said, powerpc and s390 should at least look at maybe adding a > > check for the page ref in their gup paths too. Powerpc has the special > > gup_hugepte() case, and s390 has its own version of gup entirely. I > > was actually hoping the s390 guys would look at using the generic gup > > code. > > We did look at converting the s390 gup code to CONFIG_HAVE_GENERIC_GUP, > there are some details that need careful consideration. The top one > is access_ok(), for s390 we always return true. The generic gup code > relies on the fact that a page table walk with a specific address is > doable if access_ok() returned true, the s390 specific check is slightly > different: > > if ((end <= start) || (end > mm->context.asce_limit)) > return 0; > > The obvious approach would be to modify access_ok() to check against > the asce_limit. I will try and see if anything breaks, e.g. the automatic > page table upgrade. I tested the waters in regard to access_ok() and the generic gup code. The good news is that mm/gup.c with CONFIG_HAVE_GENERIC_GUP=y seems to work just fine if the access_ok() issue is taken care of. But.. Bloat-o-meter with a non-empty uaccess_ok() that checks against current->mm->context.asce_limit: add/remove: 8/2 grow/shrink: 611/11 up/down: 61352/-1914 (59438) with CONFIG_HAVE_GENERIC_GUP on top of that add/remove: 10/2 grow/shrink: 612/12 up/down: 63568/-3280 (60288) This is not nice, would a patch like the following be acceptable? -- Subject: [PATCH] mm: introduce mm_pgd_walk_ok Add the architecture overrideable function mm_pgd_walk_ok() to check if a block of memory is inside the limits of the page table hierarchy of a given mm struct. Signed-off-by: Martin Schwidefsky --- include/asm-generic/pgtable.h | 4 ++++ mm/gup.c | 4 ++-- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index fa782fba51ee..7d2a8a58f1c1 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -1186,4 +1186,8 @@ static inline bool arch_has_pfn_modify_check(void) #define mm_pmd_folded(mm) __is_defined(__PAGETABLE_PMD_FOLDED) #endif +#ifndef mm_pgd_walk_ok +#define mm_pgd_walk_ok(mm, addr, size) access_ok(addr, size) +#endif + #endif /* _ASM_GENERIC_PGTABLE_H */ diff --git a/mm/gup.c b/mm/gup.c index 91819b8ad9cc..b3eb3f45d237 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1990,7 +1990,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; - if (unlikely(!access_ok((void __user *)start, len))) + if (unlikely(!mm_pgd_walk_ok(current->mm, (void __user *)start, len))) return 0; /* @@ -2044,7 +2044,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, if (nr_pages <= 0) return 0; - if (unlikely(!access_ok((void __user *)start, len))) + if (unlikely(!mm_pgd_walk_ok(current->mm, (void __user *)start, len))) return -EFAULT; if (gup_fast_permitted(start, nr_pages)) { -- 2.16.4 With an empty access_ok() but a "real" mm_pgd_walk_ok() the results are much more reasonable: add/remove: 2/0 grow/shrink: 2/1 up/down: 2186/-1382 (804) -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.