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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id D1B57CD5BAC for ; Thu, 21 May 2026 14:36:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:Cc:To:From: Subject:Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=qcxdHOKzYSh28oVM+92+Sl2qXUwj5KIsOOEhTqQ5qbU=; b=Q0riUAaMIevYWg0ws27VSieoox R0EcG0dluGoTqAQKuuiDe6jPra/MGoNbv0MLg7JZlAJkihE0Xq67wEDfz4vfb3gq2nZb8FaJZAATR RQHtL8v0jJuNlnb4pRXZT2sAxY7oyGyDPeBmT8ipT9U51G8V4Y4nnBNZN7BvllvbZpBpZVHQiMMTG HAzmsBtANoc3JHB2MFbuqIY/BwD5ZNMCLQzvDwrZmguNSnF5qiSmXlS/omwR+o+sQsjA7/6qwhwBK kKG/gZD8sywvhPEOue4KF03W/VkTe3ZTg/TYlOndx1rQ1BKzyfpzfVaGFq8a6Qv0Trc037OntpiC2 l63xT3WQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQ4Vr-000000085jq-3TuX; Thu, 21 May 2026 14:36:39 +0000 Received: from mail-ed1-x54a.google.com ([2a00:1450:4864:20::54a]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQ4Vn-000000085gP-1d7L for linux-arm-kernel@lists.infradead.org; Thu, 21 May 2026 14:36:36 +0000 Received: by mail-ed1-x54a.google.com with SMTP id 4fb4d7f45d1cf-67fd8c53ccdso1527279a12.3 for ; Thu, 21 May 2026 07:36:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1779374193; x=1779978993; darn=lists.infradead.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=qcxdHOKzYSh28oVM+92+Sl2qXUwj5KIsOOEhTqQ5qbU=; b=u4hWV0pVkTRErBopzBX9CgOkBYI3XPMrMcbJusfX4/vB3J0avWR2B/q2jej7aTkgv6 QSuefatqOUMnYiJxF8xdf+jXJBgJL33y/f71NYBMCY40u/uk/eeP+5LnIpo4X1Suv0rM UKeEGZlDmZ3fVT/nMAsbhvhcAKEbadWNnf4xorXYYAtIK9oHf9+rFsd8LmRF6f5hGvgG 3lT8ch5GYKCy8Yj5Aw6Z6R9GYwGvH7Z7OnQAWIHMy9+q/VMw7F8D/N4XIi8CNxJVq6GC WPkIvLiblBVv+AicFdoas/kJF5eSoZ737FG3VcNM1oglbay0W742ShyKWNy7modQp4PM uY3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779374193; x=1779978993; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=qcxdHOKzYSh28oVM+92+Sl2qXUwj5KIsOOEhTqQ5qbU=; b=em49n48+AnO0uQ5DcGYsJXaEPCMkLNWKog2lCKghn8SQtnbV+IgiSJxgxc0XkcwzzG irFJuCC8C4fbLH9IDA5q5hy+FYpT+BiLic3qNzsv1RRV8dQRD0mnqbFWbhs6uSMoSUT2 45lPFnazf76TIc3zmAI/fMCoPKblILesWeDLwcLR07r5kzAPC6hgqv9bPOGWaj90ydRZ IOnRzAhGYaeY4mJmktlVpl4KpB3xSAjEH6tk5SCOkLmxuV3HG6rw3l9kvEAXOvw0frB1 T0S2x+Ue5atnfwA/jOYPVlL7vzsQ/bmkE1iGCEfFstytt3aEVFYfylISOUbePMNlvoaD MdFQ== X-Gm-Message-State: AOJu0YwjGg7QUaqMdjZCEodLz8nbNe3EpFKqxBcjkiW39kANUUdApSdm VjoMcyVQyb0RWm92LR2zymrkjOtwqsu2dddwV/GwE74TvsRpPJz7MD+Q89yCgfWWdbAnY7VQFNt O8zMQ2ki6IiZRDWGRkx240Q== X-Received: from edvr23.prod.google.com ([2002:a05:6402:197:b0:683:5306:a54f]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6402:a28b:20b0:688:24dc:9152 with SMTP id 4fb4d7f45d1cf-688367d4eddmr1089728a12.16.1779374192287; Thu, 21 May 2026 07:36:32 -0700 (PDT) Date: Thu, 21 May 2026 15:36:26 +0100 In-Reply-To: <20260521143626.1005660-1-vdonnefort@google.com> Mime-Version: 1.0 References: <20260521143626.1005660-1-vdonnefort@google.com> X-Mailer: git-send-email 2.54.0.746.g67dd491aae-goog Message-ID: <20260521143626.1005660-4-vdonnefort@google.com> Subject: [RESEND v3 3/3] KVM: arm64: Add fail-safe for refcounted pages in __pkvm_hyp_donate_host From: Vincent Donnefort To: maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kernel-team@android.com, qperret@google.com, tabba@google.com, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260521_073635_445228_AD452236 X-CRM114-Status: GOOD ( 10.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org A previous bug in __pkvm_init_vm error path showed that the hypervisor could leak refcounted pages, (i.e. losing access to a page while its refcount is still elevated). This poses a threat to the pKVM state machine. Address this by introducing a fail-safe in __pkvm_hyp_donate_host. Transitions are not a hot path so added security is worth the extra check. Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Signed-off-by: Vincent Donnefort diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 986e0ac1f2d8..fee55e49c132 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -854,6 +854,16 @@ static int __hyp_check_page_state_range(phys_addr_t phys, u64 size, enum pkvm_pa return 0; } +static int __hyp_check_page_count_range(phys_addr_t phys, u64 size) +{ + for_each_hyp_page(page, phys, size) { + if (page->refcount) + return -EBUSY; + } + + return 0; +} + static bool guest_pte_is_poisoned(kvm_pte_t pte) { if (kvm_pte_valid(pte)) @@ -1052,7 +1062,6 @@ int __pkvm_guest_unshare_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn) int __pkvm_host_unshare_hyp(u64 pfn) { u64 phys = hyp_pfn_to_phys(pfn); - u64 virt = (u64)__hyp_va(phys); u64 size = PAGE_SIZE; int ret; @@ -1065,10 +1074,9 @@ int __pkvm_host_unshare_hyp(u64 pfn) ret = __hyp_check_page_state_range(phys, size, PKVM_PAGE_SHARED_BORROWED); if (ret) goto unlock; - if (hyp_page_count((void *)virt)) { - ret = -EBUSY; + ret = __hyp_check_page_count_range(phys, size); + if (ret) goto unlock; - } __hyp_set_page_state_range(phys, size, PKVM_NOPAGE); WARN_ON(__host_set_page_state_range(phys, size, PKVM_PAGE_OWNED)); @@ -1131,6 +1139,10 @@ int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages) if (ret) goto unlock; + ret = __hyp_check_page_count_range(phys, size); + if (ret) + goto unlock; + __hyp_set_page_state_range(phys, size, PKVM_NOPAGE); WARN_ON(kvm_pgtable_hyp_unmap(&pkvm_pgtable, virt, size) != size); WARN_ON(host_stage2_set_owner_locked(phys, size, PKVM_ID_HOST)); -- 2.54.0.746.g67dd491aae-goog