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=-18.8 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,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,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 46838C2D0E4 for ; Tue, 24 Nov 2020 18:33:33 +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 A9AD320637 for ; Tue, 24 Nov 2020 18:33:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="yFzlyxIw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A9AD320637 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.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:Subject:MIME-Version:Message-ID:In-Reply-To:Date: References:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=oYo06f5FWdZ+b/peCI20mhgXXxJEkjqhyKiYhuP54Aw=; b=yFzlyxIwGQQY+yL4YaUYAHNDl 9+dicSIUQub/h8D+WaFds7meLdSktGNf1Ok3qgqakkxGR5GLuAqvpr3wjRyUD0BRB+juW5RX3crbn hBH5yn9hERjVq2fTB1/xjucBzVYv68mUCFjMtN2xux60rEy/gAg2YWq3T/FzYC4KptR40dOEEo+eA RRg61poRq5j7lyH2yA+JO5s0F+vz9a803TBwa/fi0eWr8DO91s2EKQPaiWRuBETrUK8PQp4JlRmXj Q3qjS5U7I9F4CAwHo96cShAAhxt+E6fCJHXpoQMfsis+qAKIPp/hJxzTsnKi5ysz2wNnR+rFVx7Wz fR15kRjCA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1khd85-0001Pk-9T; Tue, 24 Nov 2020 18:33:29 +0000 Received: from out01.mta.xmission.com ([166.70.13.231]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1khd82-0001PD-Py for linux-mediatek@lists.infradead.org; Tue, 24 Nov 2020 18:33:27 +0000 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1khd7y-00CpWM-N7; Tue, 24 Nov 2020 11:33:22 -0700 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1khd7w-005yjH-BE; Tue, 24 Nov 2020 11:33:22 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Miles Chen References: <20201123063835.18981-1-miles.chen@mediatek.com> Date: Tue, 24 Nov 2020 12:32:56 -0600 In-Reply-To: <20201123063835.18981-1-miles.chen@mediatek.com> (Miles Chen's message of "Mon, 23 Nov 2020 14:38:35 +0800") Message-ID: <87lfeqsizr.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1khd7w-005yjH-BE; ; ; mid=<87lfeqsizr.fsf@x220.int.ebiederm.org>; ; ; hst=in02.mta.xmission.com; ; ; ip=68.227.160.95; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX1/cWINijvy8cfZD9GCnZGUD9VbnS+lLulo= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [RESEND PATCH v1] proc: use untagged_addr() for pagemap_read addresses X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201124_133326_898697_8CBAF64E X-CRM114-Status: GOOD ( 26.33 ) 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: wsd_upstream@mediatek.com, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Alexey Dobriyan 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 Miles Chen writes: > 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 Sigh this patch is buggy. > === 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); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Arguably the line above is safe, but unfortunately it has the possibility of suffering from overflow. > 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; Overflow handling you are removing here. > > /* I suspect the proper way to handle this is to move the test for overflow earlier so the code looks something like: end_vaddr = mm->task_size; src = *ppos; svpfn = src / PM_ENTRY_BYTES; /* watch out for wraparound */ start_vaddr = end_vaddr; if (svpfn < (ULONG_MAX >> PAGE_SHIFT)) start_vaddr = untagged_addr(svpfn << PAGE_SHIFT); /* Ensure the address is inside the task */ if (start_vaddr > mm->task_size) start_vaddr = end_vaddr; Eric _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek