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 145EC1067038 for ; Thu, 12 Mar 2026 14:16:35 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w0gpN-0004FU-CB; Thu, 12 Mar 2026 10:15:53 -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 1w0gpK-0004F4-BF for qemu-devel@nongnu.org; Thu, 12 Mar 2026 10:15:51 -0400 Received: from smtp-out2.suse.de ([195.135.223.131]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1w0gpI-0005O8-Ex for qemu-devel@nongnu.org; Thu, 12 Mar 2026 10:15:49 -0400 Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id B97375BCCA; Thu, 12 Mar 2026 14:15:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1773324946; h=from:from:reply-to: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=awvffkyqIimVaSjjWIvkUuZ+0tnQKdyQs4bNFb37EQA=; b=y92SN5JO/wvzDKYffKoJ1PZ3XZ3KSlAdy9HZzaKkPXaJspBXPCdCQY5Gy9e7kcm7U0VqUK hpSFlskiuqQpPyyBJTsp8rza9sti9W4Kl6qAF5eZvFi+T4y181S96DCqRbmKFPRCRrDknK Zbc3PgkkZeHSllxZK0X+017fKj1D/HU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1773324946; h=from:from:reply-to: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=awvffkyqIimVaSjjWIvkUuZ+0tnQKdyQs4bNFb37EQA=; b=2LkPeBNLZDoh5t8VQZO9/NtbPzUwP8+A1328gj1O5qbQWc2Sq3EpZxv59pavplrylXjZz6 Xu44F2uyXL2yY7AQ== Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=y92SN5JO; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=2LkPeBNL DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1773324946; h=from:from:reply-to: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=awvffkyqIimVaSjjWIvkUuZ+0tnQKdyQs4bNFb37EQA=; b=y92SN5JO/wvzDKYffKoJ1PZ3XZ3KSlAdy9HZzaKkPXaJspBXPCdCQY5Gy9e7kcm7U0VqUK hpSFlskiuqQpPyyBJTsp8rza9sti9W4Kl6qAF5eZvFi+T4y181S96DCqRbmKFPRCRrDknK Zbc3PgkkZeHSllxZK0X+017fKj1D/HU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1773324946; h=from:from:reply-to: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=awvffkyqIimVaSjjWIvkUuZ+0tnQKdyQs4bNFb37EQA=; b=2LkPeBNLZDoh5t8VQZO9/NtbPzUwP8+A1328gj1O5qbQWc2Sq3EpZxv59pavplrylXjZz6 Xu44F2uyXL2yY7AQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 444853FFEA; Thu, 12 Mar 2026 14:15:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PAZHA5LKsmm2aAAAD6G6ig (envelope-from ); Thu, 12 Mar 2026 14:15:46 +0000 From: Fabiano Rosas To: Vladimir Sementsov-Ogievskiy , Alexandr Moshkov , qemu-devel@nongnu.org Cc: Peter Maydell , "yc-core@yandex-team.ru" , Peter Xu Subject: Re: [PATCH v3] vmstate: fix subsection load name check In-Reply-To: References: <20260312102626.891359-1-dtalexundeer@yandex-team.ru> Date: Thu, 12 Mar 2026 11:15:43 -0300 Message-ID: <875x71yvzk.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_DN_EQ_ADDR_SOME(0.00)[]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCPT_COUNT_FIVE(0.00)[6]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[yandex-team.ru:email,suse.de:dkim,suse.de:mid,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Queue-Id: B97375BCCA Received-SPF: pass client-ip=195.135.223.131; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.819, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.903, 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: qemu development 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 Vladimir Sementsov-Ogievskiy writes: > On 12.03.26 13:26, Alexandr Moshkov wrote: >> When loading a subset, its name is checked for the parent prefix. The >> following bug may occur here: >> >> Let's say there is a vmstate named "virtio-blk", it has a subsection >> named "virtio-blk/subsection", and it also has another vmstate named >> "virtio" in the fields. >> Then, during the migration, when trying to load this subsection for >> "virtio", the prefix condition will pass for "virtio-blk/subsection" and >> then the migration will break, because this vmstate does not have such a >> subsection. >> >> In other words, if a field inside vmstate1 is set via vmstate2 with a >> name that is a prefix of the parent vmstate, then the field can "steal" >> a subsection belonging to the parent state. >> >> Looks like it happens because migration stream for "virtio-blk" looks >> like this: >> >> [virtio-blk header] [virtio-blk fields] [virtio-blk subsections] >> >> "virtio-blk" contains "virtio" field, so migration stream is: >> >> [virtio-blk header] [virtio header] [virtio fields] [virtio >> subsections] [virtio-blk subsections] >> >> And when we load the subsections of the "virtio" device, >> vmstate_subsection_load() uses qemu_peek_byte() to try to figure out if >> this is his subsection. This is where we encounter an error. >> >> Thus, the error occurs due to the fact that vmsd does not know how many >> subsections it has when loading (this does not appear anywhere in the >> migration stream), so it tries to load all the appropriate ones by >> names. >> >> To fix this issue, we call vmstate_get_subsection() and, in case of >> fail, ignore it, pop the VMSD stack and will try to define this >> subsection for outer VMSD >> >> Signed-off-by: Alexandr Moshkov >> --- >> migration/vmstate.c | 4 +--- >> 1 file changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/migration/vmstate.c b/migration/vmstate.c >> index 4d28364f7b..8f3a69c26e 100644 >> --- a/migration/vmstate.c >> +++ b/migration/vmstate.c >> @@ -639,9 +639,7 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd, > > more contex: > > if (strncmp(vmsd->name, idstr, strlen(vmsd->name)) != 0) { > trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(prefix)"); > /* it doesn't have a valid subsection name */ > return 0; > } > > If go this way, I think this check for prefix ^^^ should be removed. > +1