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=-3.8 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 autolearn=no 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 1C1E2C83004 for ; Tue, 28 Apr 2020 19:40:18 +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 C92C82076A for ; Tue, 28 Apr 2020 19:40:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ktUH8aHs" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C92C82076A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=NedyWF8h2cLLqQL7Dp0pZE+ekfMSGXRZk7FmqEyj230=; b=ktUH8aHsbzY3H3 NrvY2+QcIMCpV8J2Ru2gd1dw9WpaJthmM3S5arCff6I9CMtAr9LpqcVi0uQiiJQJbmfetaAXRPf+b 4dRWACosRzuSAu3DEEDidX35GTf/XQy9yVHnWLYHrvJUNMzBuyzHaprohL12sXLYCRWwavnz+TcvX UAK4El2IkGDA5wVMpC9RH3Fq1iYHRLZEYfKAm7J+OW7WnFMBhPbxZT7pAOv21urBS3LBDIlkwvc+X l1s3CX7h3NZTOiW92emwhS4B+DT7IA7B4kfAVZoYuBl5W7LHvZV2MY5JNQu2p4HnV90laomDVD1s0 niThSUCMQsv3Njgn7LZw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTW5W-0005Nt-F5; Tue, 28 Apr 2020 19:40:14 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTW5S-00056X-SU for linux-arm-kernel@lists.infradead.org; Tue, 28 Apr 2020 19:40:12 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3E5C5C14; Tue, 28 Apr 2020 12:40:10 -0700 (PDT) Received: from C02TF0J2HF1T.local (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DE6B73F68F; Tue, 28 Apr 2020 12:40:05 -0700 (PDT) Date: Tue, 28 Apr 2020 20:40:01 +0100 From: Catalin Marinas To: Kevin Brodsky Subject: Re: [PATCH v3 20/23] fs: Allow copy_mount_options() to access user-space in a single pass Message-ID: <20200428194001.GB35158@C02TF0J2HF1T.local> References: <20200421142603.3894-1-catalin.marinas@arm.com> <20200421142603.3894-21-catalin.marinas@arm.com> <9544d86b-d445-3497-fbbf-56c590400f83@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <9544d86b-d445-3497-fbbf-56c590400f83@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200428_124011_304558_AD575E82 X-CRM114-Status: GOOD ( 18.95 ) 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-arch@vger.kernel.org, Richard Earnshaw , Szabolcs Nagy , Andrey Konovalov , Peter Collingbourne , linux-mm@kvack.org, Alexander Viro , Vincenzo Frascino , Will Deacon , linux-arm-kernel@lists.infradead.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 On Tue, Apr 28, 2020 at 07:16:29PM +0100, Kevin Brodsky wrote: > On 21/04/2020 15:26, Catalin Marinas wrote: > > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > > index 32fc8061aa76..566da441eba2 100644 > > --- a/arch/arm64/include/asm/uaccess.h > > +++ b/arch/arm64/include/asm/uaccess.h > > @@ -416,6 +416,17 @@ extern unsigned long __must_check __arch_copy_in_user(void __user *to, const voi > > #define INLINE_COPY_TO_USER > > #define INLINE_COPY_FROM_USER > > +static inline bool arch_has_exact_copy_from_user(unsigned long n) > > +{ > > + /* > > + * copy_from_user() aligns the source pointer if the size is greater > > + * than 15. Since all the loads are naturally aligned, they can only > > + * fail on the first byte. > > + */ > > + return n > 15; > > +} > > +#define arch_has_exact_copy_from_user > > + > > extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n); > > static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n) > > { > > diff --git a/fs/namespace.c b/fs/namespace.c > > index a28e4db075ed..8febc50dfc5d 100644 > > --- a/fs/namespace.c > > +++ b/fs/namespace.c > > @@ -3025,13 +3025,16 @@ void *copy_mount_options(const void __user * data) > > if (!copy) > > return ERR_PTR(-ENOMEM); > > - size = PAGE_SIZE - offset_in_page(data); > > + size = PAGE_SIZE; > > + if (!arch_has_exact_copy_from_user(size)) > > + size -= offset_in_page(data); > > - if (copy_from_user(copy, data, size)) { > > + if (copy_from_user(copy, data, size) == size) { > > kfree(copy); > > return ERR_PTR(-EFAULT); > > } > > if (size != PAGE_SIZE) { > > + WARN_ON(1); > > I'm not sure I understand the rationale here. If we don't have exact > copy_from_user for size, then we will attempt to copy up to the end of the > page. Assuming this doesn't fault, we then want to carry on copying from the > start of the next page, until we reach a total size of up to 4K. Why would > we warn in that case? We shouldn't warn, thanks for spotting this. I added it for some testing and somehow ended up in the commit. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel