From patchwork Sat Aug 5 19:41:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 1817387 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4RJCfK0Z5qz1yYl for ; Sun, 6 Aug 2023 05:42:33 +1000 (AEST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qSN9c-0007aC-8u; Sat, 05 Aug 2023 15:41:36 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qSN9a-0007Z0-9h; Sat, 05 Aug 2023 15:41:34 -0400 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qSN9Y-0007rZ-M7; Sat, 05 Aug 2023 15:41:34 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 2862A1865E; Sat, 5 Aug 2023 22:41:50 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id EF2FA1BA44; Sat, 5 Aug 2023 22:41:27 +0300 (MSK) Received: (nullmailer pid 70352 invoked by uid 1000); Sat, 05 Aug 2023 19:41:27 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Hawkins Jiawei , =?utf-8?q?E?= =?utf-8?q?ugenio_P=C3=A9rez?= , "Michael S . Tsirkin" , Michael Tokarev Subject: [Stable-8.0.4 65/71] vdpa: Fix possible use-after-free for VirtQueueElement Date: Sat, 5 Aug 2023 22:41:06 +0300 Message-Id: <20230805194127.70304-2-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Hawkins Jiawei QEMU uses vhost_handle_guest_kick() to forward guest's available buffers to the vdpa device in SVQ avail ring. In vhost_handle_guest_kick(), a `g_autofree` `elem` is used to iterate through the available VirtQueueElements. This `elem` is then passed to `svq->ops->avail_handler`, specifically to the vhost_vdpa_net_handle_ctrl_avail(). If this handler fails to process the CVQ command, vhost_handle_guest_kick() regains ownership of the `elem`, and either frees it or requeues it. Yet the problem is that, vhost_vdpa_net_handle_ctrl_avail() mistakenly frees the `elem`, even if it fails to forward the CVQ command to vdpa device. This can result in a use-after-free for the `elem` in vhost_handle_guest_kick(). This patch solves this problem by refactoring vhost_vdpa_net_handle_ctrl_avail() to only freeing the `elem` if it owns it. Fixes: bd907ae4b0 ("vdpa: manual forward CVQ buffers") Signed-off-by: Hawkins Jiawei Message-Id: Reviewed-by: Eugenio Pérez Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin (cherry picked from commit 031b1abacbdb3f4e016b6b926f7e7876c05339bb) Signed-off-by: Michael Tokarev diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c index 2086a92965..7c2c4fb7ea 100644 --- a/net/vhost-vdpa.c +++ b/net/vhost-vdpa.c @@ -790,7 +790,16 @@ out: error_report("Bad device CVQ written length"); } vhost_svq_push_elem(svq, elem, MIN(in_len, sizeof(status))); - g_free(elem); + /* + * `elem` belongs to vhost_vdpa_net_handle_ctrl_avail() only when + * the function successfully forwards the CVQ command, indicated + * by a non-negative value of `dev_written`. Otherwise, it still + * belongs to SVQ. + * This function should only free the `elem` when it owns. + */ + if (dev_written >= 0) { + g_free(elem); + } return dev_written < 0 ? dev_written : 0; }