From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0BDED606A31C for ; Mon, 19 Oct 2026 16:19:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=YN/nMrRR Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xIq5S-0006j5-Sz; Mon, 19 Oct 2026 12:19:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xIq5R-0006ih-Aj for qemu-devel@nongnu.org; Mon, 19 Oct 2026 12:19:45 -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 1xIq5P-0000cM-6j for qemu-devel@nongnu.org; Mon, 19 Oct 2026 12:19:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1792426780; 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=pxcuucpGqCFNoLT/SJgKWSZtElBD6o9rt72QwCCLwhE=; b=YN/nMrRRyfUQEqRQBDBLSCsvmNzwYvPajYBwcXEUi67gtoVahAAu8yLwq+e5guIHgCeyOg HQPTeHG1KZVokHIlbB4iy09Gb9ZnWImVGIj9UM7iH1aWiV7CP2T/vVG0/x85QQdFbJt2UY 1StK6gW4ImJeLNGE10PCJdx9uZ+wwmA= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-364-8Vxn1nvpOwyNDIuIyitF9w-1; Mon, 19 Oct 2026 16:19:36 +0000 X-MC-Unique: 8Vxn1nvpOwyNDIuIyitF9w-1 X-Mimecast-MFC-AGG-ID: 8Vxn1nvpOwyNDIuIyitF9w_1792426775 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E89CE18005B8; Mon, 19 Oct 2026 16:19:34 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7C07E30000E3; Mon, 19 Oct 2026 16:19:32 +0000 (UTC) Date: Mon, 19 Oct 2026 11:19:29 -0500 From: Eric Blake To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Paolo Bonzini , qemu-block@nongnu.org, Fam Zheng , Benjamin Marzinski , kwolf@redhat.com, Dan Berrange Subject: Re: [PATCH] qemu-pr-helper: do not free reply when multipath_process_cmd() fails Message-ID: References: <20261019153353.105505-1-stefanha@redhat.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261019153353.105505-1-stefanha@redhat.com> User-Agent: NeoMutt/20260616 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.329, 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_H3=0.001, RCVD_IN_MSPIKE_WL=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: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, RCVD_IN_DNSWL_BLOCKED,RCVD_IN_ZEN_BLOCKED_OPENDNS,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Oct 19, 2026 at 11:33:53AM -0400, Stefan Hajnoczi wrote: > Kevin Wolf pointed out that the multipath_process_cmd() documentation > only defines the value of reply on success. Don't touch it when the > function returns -1. > > The libmpathcmd implementation as of c78cf64a9e8e does not set *reply to > NULL when its internal mpath_send_cmd() call fails, so I think Kevin's > interpretation is correct. > > As it stands, there is no observable bug in the QEMU code though because > reply is initialized to NULL before calling multipath_process_cmd(). > This patch is just a cleanup. > > Cc: Benjamin Marzinski > Cc: kwolf@redhat.com > Cc: eblake@redhat.com > Signed-off-by: Stefan Hajnoczi > --- > Eric pointed out that g_autofree could eliminate the manual free(3) > calls. In this case we cannot use it since g_autofree calls glib's > g_free() rather than the standard library's free(3). I know glib encourages g_free() in case malloc was interposed, but aren't we guaranteed that we are not exploiting glib's malloc overrides, and therefore g_free() calls into free(3)? But I'm fine with your decision to not use g_autofree here. > --- > scsi/qemu-pr-helper.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/scsi/qemu-pr-helper.c b/scsi/qemu-pr-helper.c > index 54d196a503f..d52109cab25 100644 > --- a/scsi/qemu-pr-helper.c > +++ b/scsi/qemu-pr-helper.c > @@ -571,13 +571,17 @@ static bool multipathd_cmd(int fd, const char *cmd, Error **errp) > free(reply); > return false; > } > - free(reply); > if (ret == -1) { > + /* > + * reply is not freed because the documentation only defines it when > + * the function returns success. > + */ > error_setg_errno(errp, last_errno, > "mpath_process_cmd(%d, \"%s\") failed", > fd, cmd); > return false; > } > + free(reply); Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. Virtualization: qemu.org | libguestfs.org