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=-18.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D4C66C63777 for ; Thu, 26 Nov 2020 07:16:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B0282075A for ; Thu, 26 Nov 2020 07:16:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388379AbgKZHQ0 convert rfc822-to-8bit (ORCPT ); Thu, 26 Nov 2020 02:16:26 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:4103 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729631AbgKZHQ0 (ORCPT ); Thu, 26 Nov 2020 02:16:26 -0500 Received: from DGGEMM404-HUB.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4ChTZC4LNgzXgMb; Thu, 26 Nov 2020 15:16:03 +0800 (CST) Received: from dggemi759-chm.china.huawei.com (10.1.198.145) by DGGEMM404-HUB.china.huawei.com (10.3.20.212) with Microsoft SMTP Server (TLS) id 14.3.487.0; Thu, 26 Nov 2020 15:16:21 +0800 Received: from dggemi761-chm.china.huawei.com (10.1.198.147) by dggemi759-chm.china.huawei.com (10.1.198.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Thu, 26 Nov 2020 15:16:21 +0800 Received: from dggemi761-chm.china.huawei.com ([10.9.49.202]) by dggemi761-chm.china.huawei.com ([10.9.49.202]) with mapi id 15.01.1913.007; Thu, 26 Nov 2020 15:16:21 +0800 From: "Song Bao Hua (Barry Song)" To: Miles Chen , Alexey Dobriyan , Andrew Morton CC: "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , "wsd_upstream@mediatek.com" Subject: RE: [RESEND PATCH v1] proc: use untagged_addr() for pagemap_read addresses Thread-Topic: [RESEND PATCH v1] proc: use untagged_addr() for pagemap_read addresses Thread-Index: AQHWwWNz5MRhXZKR2UCNja39TEhHcanaA0sg Date: Thu, 26 Nov 2020 07:16:21 +0000 Message-ID: <24d32889abb1412abcd4e868a36783f9@hisilicon.com> References: <20201123063835.18981-1-miles.chen@mediatek.com> In-Reply-To: <20201123063835.18981-1-miles.chen@mediatek.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.126.202.201] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Miles Chen [mailto:miles.chen@mediatek.com] > Sent: Monday, November 23, 2020 7:39 PM > To: Alexey Dobriyan ; Andrew Morton > > Cc: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org; > linux-mediatek@lists.infradead.org; wsd_upstream@mediatek.com; Miles > Chen > Subject: [RESEND PATCH v1] proc: use untagged_addr() for pagemap_read > addresses > > 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(). > > I tested with 5.10-rc4 and the issue remains. > > My test code is baed on [1]: > > A userspace pointer which has been tagged by 0xb4: 0xb400007662f541c8 > > === userspace program === > > uint64 OsLayer::VirtualToPhysical(void *vaddr) { > uint64 frame, paddr, pfnmask, pagemask; > int pagesize = sysconf(_SC_PAGESIZE); > off64_t off = ((uintptr_t)vaddr) / pagesize * 8; // off = > 0xb400007662f541c8 / pagesize * 8 = 0x5a00003b317aa0 > int fd = open(kPagemapPath, O_RDONLY); > ... > > if (lseek64(fd, off, SEEK_SET) != off || read(fd, &frame, 8) != 8) { > int err = errno; > string errtxt = ErrorString(err); > if (fd >= 0) > close(fd); > return 0; > } > ... > } > > === kernel fs/proc/task_mmu.c === > > static ssize_t pagemap_read(struct file *file, char __user *buf, > size_t count, loff_t *ppos) > { > ... > src = *ppos; > svpfn = src / PM_ENTRY_BYTES; // svpfn == 0xb400007662f54 > start_vaddr = svpfn << PAGE_SHIFT; // start_vaddr == > 0xb400007662f54000 > end_vaddr = mm->task_size; > > /* watch out for wraparound */ > // svpfn == 0xb400007662f54 > // (mm->task_size >> PAGE) == 0x8000000 > if (svpfn > mm->task_size >> PAGE_SHIFT) // the condition is true because > of the tag 0xb4 > start_vaddr = end_vaddr; > > ret = 0; > while (count && (start_vaddr < end_vaddr)) { // we cannot visit correct > entry because start_vaddr is set to end_vaddr > int len; > unsigned long end; > ... > } > ... > } > > [1] > https://github.com/stressapptest/stressapptest/blob/master/src/os.cc#L158 > > Signed-off-by: Miles Chen > --- > fs/proc/task_mmu.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 217aa2705d5d..e9a70f7ee515 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1599,11 +1599,11 @@ static ssize_t pagemap_read(struct file *file, char > __user *buf, > > src = *ppos; > svpfn = src / PM_ENTRY_BYTES; > - start_vaddr = svpfn << PAGE_SHIFT; > + start_vaddr = untagged_addr(svpfn << PAGE_SHIFT); > end_vaddr = mm->task_size; > > /* watch out for wraparound */ > - if (svpfn > mm->task_size >> PAGE_SHIFT) > + if (start_vaddr > mm->task_size) > start_vaddr = end_vaddr; Wouldn't the untag be done by the user reading pagemap file? With this patch, even users pass an illegal address, for example, users put a tag on a virtual address which hasn't really a tag, they will still get the right pagemap. > > /* > -- > 2.18.0 Thanks Barry