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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 4FEE8C4332F for ; Mon, 21 Nov 2022 21:20:29 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oxECd-0002A3-JS; Mon, 21 Nov 2022 16:19:43 -0500 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 1oxECX-00027z-8I for qemu-devel@nongnu.org; Mon, 21 Nov 2022 16:19:38 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oxECU-0007Ba-Pl for qemu-devel@nongnu.org; Mon, 21 Nov 2022 16:19:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669065570; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=jkloZE2WADCy1fRXSTYkasFd2UOgtFZHIwKHqDTLSzU=; b=Zv//REusKZyaCHd+vUfu9TFsZouu59m02XN/Me8y1aH0HKpPn/57J/2FR97z8F6+w9PZ/I 7jBVwNuQ9ogsrrU27VRdiG45DJCf2Wm3qFw20wAK1Tnnvqf1CpF16oTDEO8IBOoWSgrlUm QVfGIyBKOxtRwZByo6ICLGjeURHY6LI= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-448-m9T-wVaHPjyQB-ah1S2E3A-1; Mon, 21 Nov 2022 16:19:28 -0500 X-MC-Unique: m9T-wVaHPjyQB-ah1S2E3A-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8573829ABA02; Mon, 21 Nov 2022 21:19:28 +0000 (UTC) Received: from localhost (unknown [10.39.192.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9B0F04EA47; Mon, 21 Nov 2022 21:19:27 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: , Hanna Reitz , Kevin Wolf , Stefan Hajnoczi , Jonathan Cameron Subject: [PATCH for-7.2] block-backend: avoid bdrv_unregister_buf() NULL pointer deref Date: Mon, 21 Nov 2022 16:19:23 -0500 Message-Id: <20221121211923.1993171-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org bdrv_*() APIs expect a valid BlockDriverState. Calling them with bs=NULL leads to undefined behavior. Jonathan Cameron reported this following NULL pointer dereference when a VM with a virtio-blk device and a memory-backend-file object is terminated: 1. qemu_cleanup() closes all drives, setting blk->root to NULL 2. qemu_cleanup() calls user_creatable_cleanup(), which results in a RAM block notifier callback because the memory-backend-file is destroyed. 3. blk_unregister_buf() is called by virtio-blk's BlockRamRegistrar notifier callback and undefined behavior occurs. Fixes: baf422684d73 ("virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint") Co-authored-by: Jonathan Cameron Signed-off-by: Stefan Hajnoczi --- block/block-backend.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/block/block-backend.c b/block/block-backend.c index b48c91f4e1..d98a96ff37 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -2576,14 +2576,25 @@ static void blk_root_drained_end(BdrvChild *child, int *drained_end_counter) bool blk_register_buf(BlockBackend *blk, void *host, size_t size, Error **errp) { + BlockDriverState *bs = blk_bs(blk); + GLOBAL_STATE_CODE(); - return bdrv_register_buf(blk_bs(blk), host, size, errp); + + if (bs) { + return bdrv_register_buf(bs, host, size, errp); + } + return true; } void blk_unregister_buf(BlockBackend *blk, void *host, size_t size) { + BlockDriverState *bs = blk_bs(blk); + GLOBAL_STATE_CODE(); - bdrv_unregister_buf(blk_bs(blk), host, size); + + if (bs) { + bdrv_unregister_buf(bs, host, size); + } } int coroutine_fn blk_co_copy_range(BlockBackend *blk_in, int64_t off_in, -- 2.38.1