From patchwork Thu Apr 16 15:45:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 11493257 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 19A1481 for ; Thu, 16 Apr 2020 15:46:14 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 003B921927 for ; Thu, 16 Apr 2020 15:46:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 003B921927 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jP6hm-00062O-Jg; Thu, 16 Apr 2020 15:45:30 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jP6hl-00062G-8s for xen-devel@lists.xenproject.org; Thu, 16 Apr 2020 15:45:29 +0000 X-Inumbo-ID: 4bc17702-7ff9-11ea-b58d-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 4bc17702-7ff9-11ea-b58d-bc764e2007e4; Thu, 16 Apr 2020 15:45:28 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 4A5A6AB5C; Thu, 16 Apr 2020 15:45:27 +0000 (UTC) Subject: [PATCH 2/6] x86/mem-paging: correct p2m_mem_paging_prep()'s error handling From: Jan Beulich To: "xen-devel@lists.xenproject.org" References: <3b7cc69d-709c-570a-716a-c45f6fda181f@suse.com> Message-ID: <853d915a-4748-00c2-e065-9cd8ef63f279@suse.com> Date: Thu, 16 Apr 2020 17:45:25 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <3b7cc69d-709c-570a-716a-c45f6fda181f@suse.com> Content-Language: en-US X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Andrew Cooper , George Dunlap , Wei Liu , =?utf-8?q?R?= =?utf-8?q?oger_Pau_Monn=C3=A9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Communicating errors from p2m_set_entry() to the caller is not enough: Neither the M2P nor the stats updates should occur in such a case. Instead the allocated page needs to be freed again; for cleanliness reasons also properly take into account _PGC_allocated there. Signed-off-by: Jan Beulich --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -1781,7 +1781,7 @@ void p2m_mem_paging_populate(struct doma */ int p2m_mem_paging_prep(struct domain *d, unsigned long gfn_l, uint64_t buffer) { - struct page_info *page; + struct page_info *page = NULL; p2m_type_t p2mt; p2m_access_t a; gfn_t gfn = _gfn(gfn_l); @@ -1816,9 +1816,19 @@ int p2m_mem_paging_prep(struct domain *d goto out; /* Get a free page */ ret = -ENOMEM; - page = alloc_domheap_page(p2m->domain, 0); + page = alloc_domheap_page(d, 0); if ( unlikely(page == NULL) ) goto out; + if ( unlikely(!get_page(page, d)) ) + { + /* + * The domain can't possibly know about this page yet, so failure + * here is a clear indication of something fishy going on. + */ + domain_crash(d); + page = NULL; + goto out; + } mfn = page_to_mfn(page); page_extant = 0; @@ -1832,7 +1842,6 @@ int p2m_mem_paging_prep(struct domain *d "Failed to load paging-in gfn %lx Dom%d bytes left %d\n", gfn_l, d->domain_id, ret); ret = -EFAULT; - put_page(page); /* Don't leak pages */ goto out; } } @@ -1843,13 +1852,24 @@ int p2m_mem_paging_prep(struct domain *d ret = p2m_set_entry(p2m, gfn, mfn, PAGE_ORDER_4K, paging_mode_log_dirty(d) ? p2m_ram_logdirty : p2m_ram_rw, a); - set_gpfn_from_mfn(mfn_x(mfn), gfn_l); + if ( !ret ) + { + set_gpfn_from_mfn(mfn_x(mfn), gfn_l); - if ( !page_extant ) - atomic_dec(&d->paged_pages); + if ( !page_extant ) + atomic_dec(&d->paged_pages); + } out: gfn_unlock(p2m, gfn, 0); + + if ( page ) + { + if ( ret ) + put_page_alloc_ref(page); + put_page(page); + } + return ret; }