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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 347DACCA47B for ; Tue, 5 Jul 2022 12:11:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235182AbiGEMLk (ORCPT ); Tue, 5 Jul 2022 08:11:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46094 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234018AbiGEMGW (ORCPT ); Tue, 5 Jul 2022 08:06:22 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2001118B3B; Tue, 5 Jul 2022 05:05:52 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B01CD61909; Tue, 5 Jul 2022 12:05:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92ACAC341C7; Tue, 5 Jul 2022 12:05:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657022751; bh=PXnYC5Q5J8r1ipXlW9fyoi7kFwV9c2wah0J2rCfcv6A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ALCkUBl99RwuHbIM6UZbKiv12+TRpKdZeyJFeOaNUH4eay6e3Nl/CLK0fMnj6BbuN sKtsvnEe7x0Y7jMu8fU/jG9CqJ05AbhCBNWwbLf3IaGecwO3mch3z34UNLnGf95gvt yrywMVj6+vqKfZY8eRjL7TYUFMUQQaKAzqjieiOo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oleksandr Tyshchenko , Stefano Stabellini , Juergen Gross Subject: [PATCH 5.4 55/58] xen/arm: Fix race in RB-tree based P2M accounting Date: Tue, 5 Jul 2022 13:58:31 +0200 Message-Id: <20220705115611.865637452@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220705115610.236040773@linuxfoundation.org> References: <20220705115610.236040773@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleksandr Tyshchenko commit b75cd218274e01d026dc5240e86fdeb44bbed0c8 upstream. During the PV driver life cycle the mappings are added to the RB-tree by set_foreign_p2m_mapping(), which is called from gnttab_map_refs() and are removed by clear_foreign_p2m_mapping() which is called from gnttab_unmap_refs(). As both functions end up calling __set_phys_to_machine_multi() which updates the RB-tree, this function can be called concurrently. There is already a "p2m_lock" to protect against concurrent accesses, but the problem is that the first read of "phys_to_mach.rb_node" in __set_phys_to_machine_multi() is not covered by it, so this might lead to the incorrect mappings update (removing in our case) in RB-tree. In my environment the related issue happens rarely and only when PV net backend is running, the xen_add_phys_to_mach_entry() claims that it cannot add new pfn <-> mfn mapping to the tree since it is already exists which results in a failure when mapping foreign pages. But there might be other bad consequences related to the non-protected root reads such use-after-free, etc. While at it, also fix the similar usage in __pfn_to_mfn(), so initialize "struct rb_node *n" with the "p2m_lock" held in both functions to avoid possible bad consequences. This is CVE-2022-33744 / XSA-406. Signed-off-by: Oleksandr Tyshchenko Reviewed-by: Stefano Stabellini Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman --- arch/arm/xen/p2m.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/arch/arm/xen/p2m.c +++ b/arch/arm/xen/p2m.c @@ -62,11 +62,12 @@ out: unsigned long __pfn_to_mfn(unsigned long pfn) { - struct rb_node *n = phys_to_mach.rb_node; + struct rb_node *n; struct xen_p2m_entry *entry; unsigned long irqflags; read_lock_irqsave(&p2m_lock, irqflags); + n = phys_to_mach.rb_node; while (n) { entry = rb_entry(n, struct xen_p2m_entry, rbnode_phys); if (entry->pfn <= pfn && @@ -153,10 +154,11 @@ bool __set_phys_to_machine_multi(unsigne int rc; unsigned long irqflags; struct xen_p2m_entry *p2m_entry; - struct rb_node *n = phys_to_mach.rb_node; + struct rb_node *n; if (mfn == INVALID_P2M_ENTRY) { write_lock_irqsave(&p2m_lock, irqflags); + n = phys_to_mach.rb_node; while (n) { p2m_entry = rb_entry(n, struct xen_p2m_entry, rbnode_phys); if (p2m_entry->pfn <= pfn &&