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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 3390BC71156 for ; Thu, 3 Dec 2020 11:42:58 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 B5B8E20758 for ; Thu, 3 Dec 2020 11:42:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B5B8E20758 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.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:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iePCGdbtKEbsa4/3//N+rJdrJjw2ZwCvA79uXyemKl8=; b=gy8OWcuhxQ7xXLwRf9WEAu6ph Wlw/IlnM6N/UadhZhkhcLmC8Lf5QLQ1M2anIIKZX9AN/Xmvn5CnE3PaT8KQDSZVoo9pH4jYtmuC59 3M4zmmhW07d5yggIA5udDswO6GvSPvJ0gE6birrchIecF10IYkO4PPRDzQRbOTaR0dzm809qRbVCs QePXsi3bTzxhvxTYX5U67+0qv//mrQ3Iyzzh86THbO9UrGrQiYfxrUZxXLtH31/VSv/Ad4zOdXTzj qKnTX53FxfeZkjg+lpPTfF81QBhF/qdj1Gg0w7oJOS/iHP6+JwTdHCgaRAVSCvEO7oTWYLthTB5mk eYyKeIO+Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kkn0a-0004w7-3l; Thu, 03 Dec 2020 11:42:48 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kkn0X-0004vX-5v for linux-mediatek@lists.infradead.org; Thu, 03 Dec 2020 11:42:46 +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 1D325113E; Thu, 3 Dec 2020 03:42:44 -0800 (PST) Received: from [10.37.8.53] (unknown [10.37.8.53]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4CC8E3F66B; Thu, 3 Dec 2020 03:42:40 -0800 (PST) Subject: Re: [PATCH v2] proc: use untagged_addr() for pagemap_read addresses To: Miles Chen , Alexey Dobriyan , Andrew Morton References: <20201127050738.14440-1-miles.chen@mediatek.com> From: Vincenzo Frascino Message-ID: Date: Thu, 3 Dec 2020 11:45:56 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201127050738.14440-1-miles.chen@mediatek.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201203_064245_362908_AFC6C546 X-CRM114-Status: GOOD ( 28.67 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Song Bao Hua , Marco Elver , Catalin Marinas , wsd_upstream@mediatek.com, Andrey Konovalov , Will Deacon , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Alexander Potapenko , "Eric W . Biederman" , Andrey Ryabinin , linux-fsdevel@vger.kernel.org, linux-mediatek@lists.infradead.org, Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org Hi Miles, On 11/27/20 5:07 AM, Miles Chen wrote: > When we try to visit the pagemap of a tagged userspace pointer, we find > that the start_vaddr is not correct because of the tag. > To fix it, we should untag the usespace pointers in pagemap_read(). > Nit: s/usespace/userspace/ (please search and replace all occurrences :) ) > I tested with 5.10-rc4 and the issue remains. > > Explaination from Catalin in [1]: > Nit: s/Explaination/Explanation/ (please search and replace all occurrences :) ) > " > Arguably, that's a user-space bug since tagged file offsets were never > supported. In this case it's not even a tag at bit 56 as per the arm64 > tagged address ABI but rather down to bit 47. You could say that the > problem is caused by the C library (malloc()) or whoever created the > tagged vaddr and passed it to this function. It's not a kernel > regression as we've never supported it. > > Now, pagemap is a special case where the offset is usually not generated > as a classic file offset but rather derived by shifting a user virtual > address. I guess we can make a concession for pagemap (only) and allow > such offset with the tag at bit (56 - PAGE_SHIFT + 3). > " > > My test code is baed on [2]: Nit: s/baed/based/ (please search and replace all occurrences :) ) [...] > --- > fs/proc/task_mmu.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 217aa2705d5d..92b277388f05 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1599,11 +1599,15 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, > > src = *ppos; > svpfn = src / PM_ENTRY_BYTES; > - start_vaddr = svpfn << PAGE_SHIFT; > end_vaddr = mm->task_size; > > /* watch out for wraparound */ > - if (svpfn > mm->task_size >> PAGE_SHIFT) > + start_vaddr = end_vaddr; > + if (svpfn < (ULONG_MAX >> PAGE_SHIFT)) It seems that 'svpfn' should be less-then-equal (<=) '(ULONG_MAX >> PAGE_SHIFT)'. Is there any specific reason why this is not the case? > + start_vaddr = untagged_addr(svpfn << PAGE_SHIFT); > + > + /* Ensure the address is inside the task */ > + if (start_vaddr > mm->task_size) > start_vaddr = end_vaddr; > > /* > Otherwise: Reviewed-by: Vincenzo Frascino -- Regards, Vincenzo _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek