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 ED061CA0EFF for ; Wed, 27 Aug 2025 18:15:56 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1urKfT-0005lv-Rz; Wed, 27 Aug 2025 14:14:43 -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 1urKfQ-0005kN-MK for qemu-devel@nongnu.org; Wed, 27 Aug 2025 14:14:40 -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 1urKfM-0003K9-ID for qemu-devel@nongnu.org; Wed, 27 Aug 2025 14:14:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1756318470; h=from:from:reply-to: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=tn9DBNo8i3Db/v3WYlDOutG3keQInGDYgiTWwdXJzjE=; b=UFUZ/PvYhN8U0R5JxcAC7u34vosIHb2w+we6JAcojWgW1eDmKXuY1nPdt9n0zyMCyf4jIn k+FMkHn0rIXKht1sHKJU/UY/NOeYInRNGU49+XcT2Xt6vkhxnOB8MToFfutssCz9HS+SBv B0yyat6zQ2PzVfINodEzjD7tPJThLxY= Received: from mx-prod-mc-01.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-44-GzelnyaBO4KrKdBe_vU6Kw-1; Wed, 27 Aug 2025 14:14:28 -0400 X-MC-Unique: GzelnyaBO4KrKdBe_vU6Kw-1 X-Mimecast-MFC-AGG-ID: GzelnyaBO4KrKdBe_vU6Kw_1756318467 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C03B4195609E; Wed, 27 Aug 2025 18:14:26 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.195]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C4513195419F; Wed, 27 Aug 2025 18:14:24 +0000 (UTC) Date: Wed, 27 Aug 2025 19:14:21 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Nikolai Barybin Cc: qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Ani Sinha , "Denis V. Lunev" Subject: Re: [PATCH] dump: enhance win_dump_available to report properly Message-ID: References: <20250827-enhance-win-dump-avalaible-v2-v1-1-a6f359e9ff8e@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250827-enhance-win-dump-avalaible-v2-v1-1-a6f359e9ff8e@virtuozzo.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Aug 27, 2025 at 04:15:27PM +0300, Nikolai Barybin wrote: > QMP query-dump-guest-memory-capability reports win dump as available for > any x86 VM, which is false. > > This patch implements proper query of vmcoreinfo and calculation of > guest note size. Based on that we can surely report whether win dump > available or not. > > To perform this I suggest to split dump_init() into dump_preinit() and > dump_init_complete() to avoid exausting copypaste in > win_dump_available(). > > For further reference one may review this libvirt discussion: > https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/thread/HJ3JRLWLGN3IKIC22OQ3PMZ4J3EFG5XB/#HJ3JRLWLGN3IKIC22OQ3PMZ4J3EFG5XB > [PATCH 0/4] Allow xml-configured coredump format on VM crash > > Signed-off-by: Nikolai Barybin > --- > During first series discussion Den mentions that that code will not work > on 32bit guest with more than 4Gb RAM on i386. > > This issue required even more code duplication between dump_init() and > win_dump_available() which we'd like to avoid as mentioned by Daniel. > > Hence I present 2nd version of this fix: > - split dump_init() into dump_preinit() and dump_init_complete() > - pass pre-inited dump structure with calculated guest note size to > win_dump_available() > - call header check and guest note size check inside > win_dump_available() > --- > dump/dump.c | 129 ++++++++++++++++++++++++++++++++------------------------ > dump/win_dump.c | 23 ++++++++-- > dump/win_dump.h | 2 +- > 3 files changed, 95 insertions(+), 59 deletions(-) > > diff --git a/dump/dump.c b/dump/dump.c > index 15bbcc0c6192822cf920fcb7d60eb7d2cfad0952..19341fa42feef4d1c50dbb3a892ded59a3468d20 100644 > --- a/dump/dump.c > +++ b/dump/dump.c > @@ -1777,10 +1777,7 @@ static void vmcoreinfo_update_phys_base(DumpState *s) > g_strfreev(lines); > } > > -static void dump_init(DumpState *s, int fd, bool has_format, > - DumpGuestMemoryFormat format, bool paging, bool has_filter, > - int64_t begin, int64_t length, bool kdump_raw, > - Error **errp) > +static void dump_preinit(DumpState *s, Error **errp) > { > ERRP_GUARD(); > VMCoreInfoState *vmci = vmcoreinfo_find(); > @@ -1788,16 +1785,6 @@ static void dump_init(DumpState *s, int fd, bool has_format, > int nr_cpus; > int ret; > > - s->has_format = has_format; > - s->format = format; > - s->written_size = 0; > - s->kdump_raw = kdump_raw; > - > - /* kdump-compressed is conflict with paging and filter */ > - if (has_format && format != DUMP_GUEST_MEMORY_FORMAT_ELF) { > - assert(!paging && !has_filter); > - } > - > if (runstate_is_running()) { > vm_stop(RUN_STATE_SAVE_VM); > s->resume = true; > @@ -1814,41 +1801,10 @@ static void dump_init(DumpState *s, int fd, bool has_format, > nr_cpus++; > } > > - s->fd = fd; > - if (has_filter && !length) { > - error_setg(errp, "parameter 'length' expects a non-zero size"); > - goto cleanup; > - } > - s->filter_area_begin = begin; > - s->filter_area_length = length; > - > - /* First index is 0, it's the special null name */ > - s->string_table_buf = g_array_new(FALSE, TRUE, 1); > - /* > - * Allocate the null name, due to the clearing option set to true > - * it will be 0. > - */ > - g_array_set_size(s->string_table_buf, 1); > - > memory_mapping_list_init(&s->list); > - > guest_phys_blocks_init(&s->guest_phys_blocks); > guest_phys_blocks_append(&s->guest_phys_blocks); > - s->total_size = dump_calculate_size(s); > -#ifdef DEBUG_DUMP_GUEST_MEMORY > - fprintf(stderr, "DUMP: total memory to dump: %lu\n", s->total_size); > -#endif > > - /* it does not make sense to dump non-existent memory */ > - if (!s->total_size) { > - error_setg(errp, "dump: no guest memory to dump"); > - goto cleanup; > - } > - > - /* get dump info: endian, class and architecture. > - * If the target architecture is not supported, cpu_get_dump_info() will > - * return -1. > - */ > ret = cpu_get_dump_info(&s->dump_info, &s->guest_phys_blocks); > if (ret < 0) { > error_setg(errp, > @@ -1906,6 +1862,56 @@ static void dump_init(DumpState *s, int fd, bool has_format, > } > } > > + s->nr_cpus = nr_cpus; > + return; > +cleanup: > + dump_cleanup(s); > +} The 'dump_cleanup' call is unsafe. In qmp_query_dump_guest_memory_capability we initialize 's' using 'dump_state_prepare' which just zero's the struct, aside from the 'status' field. Meanwhile 'dump_cleanup' will unconditionally do: close(s->fd); and 'fd' will be 0, as in stdin, so we break any usage of stdin that QEMU has. Then some other unlucky part of QEMU will open a FD and get given FD == 0, making things potentially even worse. We need 'dump_state_prepare' to set 's->fd = -1', and in dump_cleanup we should check for s->fd != -1, and after closing it, must set it back to '-1'. In fact, I think even the existing dump code is broken in this respect, and so this should likely be a separate fix we can send to stable. I think the 'migrate_del_blocker' call in dump_cleanup is potentially unsafe too, as it might try to delete a blocker that is not registered. > @@ -2215,6 +2224,14 @@ DumpGuestMemoryCapability *qmp_query_dump_guest_memory_capability(Error **errp) > g_new0(DumpGuestMemoryCapability, 1); > DumpGuestMemoryFormatList **tail = &cap->formats; > > + DumpState *s = &dump_state_global; > + dump_state_prepare(s); This is unsafe. Consider we have 2 distinct monitor clients. One client is in the middle of a dump operation, when another client calls query-dump-guest-memory-capability - the latter will scribble over state used by the former. We must use a local stack allocated DumpState in this query command, instead of dump_state_global. > + dump_preinit(s, errp); > + if (*errp) { > + qatomic_set(&s->status, DUMP_STATUS_FAILED); > + return cap; > + } > + > /* elf is always available */ > QAPI_LIST_APPEND(tail, DUMP_GUEST_MEMORY_FORMAT_ELF); > > @@ -2234,9 +2251,11 @@ DumpGuestMemoryCapability *qmp_query_dump_guest_memory_capability(Error **errp) > QAPI_LIST_APPEND(tail, DUMP_GUEST_MEMORY_FORMAT_KDUMP_RAW_SNAPPY); > #endif > > - if (win_dump_available(NULL)) { > + if (win_dump_available(s, NULL)) { > QAPI_LIST_APPEND(tail, DUMP_GUEST_MEMORY_FORMAT_WIN_DMP); > } > > + dump_cleanup(s); > + qatomic_set(&s->status, DUMP_STATUS_NONE); > return cap; > } With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|