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 9C277C28B2E for ; Mon, 10 Mar 2025 10:36:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1traUH-0007zu-J1; Mon, 10 Mar 2025 06:35:57 -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 1traUF-0007xz-BT for qemu-devel@nongnu.org; Mon, 10 Mar 2025 06:35:55 -0400 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 1traUB-0002VZ-UI for qemu-devel@nongnu.org; Mon, 10 Mar 2025 06:35:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741602950; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aiBhGl194zUP3tnlpGCAxgoOvKg4tv3F89gPeIt/aOU=; b=isT2tcO3Q4pRnF+GCLPF/V4sR7C0ymAmah/NButQ/Ei2idaPHI0viEa6QbGy++dRblq3Ur ZsNy0HEmDvPBf21bknZGIisFBCZXhZ6SinEiw/R+8Tz1patXJTKVXDPsSW3LgbxNydcTjd BBaXSVGUnQNSjEeIoYEH57ssvLNiszE= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-288-bN6QDz-fPPGmsqEs-8Um9A-1; Mon, 10 Mar 2025 06:35:49 -0400 X-MC-Unique: bN6QDz-fPPGmsqEs-8Um9A-1 X-Mimecast-MFC-AGG-ID: bN6QDz-fPPGmsqEs-8Um9A_1741602948 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C4F9719560AB; Mon, 10 Mar 2025 10:35:47 +0000 (UTC) Received: from redhat.com (unknown [10.45.225.222]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D2B0E1800373; Mon, 10 Mar 2025 10:35:45 +0000 (UTC) Date: Mon, 10 Mar 2025 11:35:43 +0100 From: Kevin Wolf To: gerben@altlinux.org Cc: qemu-devel@nongnu.org, hreitz@redhat.com, sdl.qemu@linuxtesting.org Subject: Re: [PATCH] block/vmdk: prevent double-free in extent memory management Message-ID: References: <20250304090415.39393-1-gerben@altlinux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250304090415.39393-1-gerben@altlinux.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@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, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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 Am 04.03.2025 um 10:04 hat gerben@altlinux.org geschrieben: > From: Denis Rastyogin > > This error was discovered by fuzzing qemu-img. > > A double-free issue in the VMDK driver occurs when handling snapshots. > The memory allocated for extent structures is freed twice: first in > vmdk_close (block/vmdk.c) and then in vmdk_add_extent (block/vmdk.c). > > The fix ensures the s->extents pointer is set to NULL after freeing, > preventing double-free. > > Closes: https://gitlab.com/qemu-project/qemu/-/issues/2853 > Signed-off-by: Denis Rastyogin > --- > block/vmdk.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/block/vmdk.c b/block/vmdk.c > index 2adec49912..d6baa54602 100644 > --- a/block/vmdk.c > +++ b/block/vmdk.c > @@ -285,6 +285,7 @@ static void vmdk_free_extents(BlockDriverState *bs) > bdrv_graph_wrunlock(); > > g_free(s->extents); > + s->extents = NULL; > } This is not the right fix. It only papers over the real bug, which is that bdrv_snapshot_goto() calls .bdrv_open() for a BlockDriverState whose bs->opaque hasn't been zeroed. Open functions of block drivers generally rely on having a zeroed state. Kevin