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 24C77D0E6DE for ; Tue, 25 Nov 2025 13:24:00 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vNt18-0004uk-Hb; Tue, 25 Nov 2025 08:23:39 -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 1vNt17-0004s6-4t for qemu-devel@nongnu.org; Tue, 25 Nov 2025 08:23:37 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vNt15-0001M6-0T for qemu-devel@nongnu.org; Tue, 25 Nov 2025 08:23:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1764077012; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=feLSS8xmQ8wpyH5IhvvP9eIyw+gMm6vVWVx5wD4zGBs=; b=LcahL7ws1wQP/o6N1gmx2yWhBbXrs+j7cacJPHiYVLuvnp2DQP7zYR+wAnHzQofJ0n9tnL 1oer5use8k0oyLULdIpFXGTepCEUXuK4GUqq25fgvCRPEIReGY72lr8B4oh9nX9CmmdMJO gIh1dpjhmqq5z8osIJCaoFoWmCVYPjA= Received: from mx-prod-mc-08.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-269-I6dymSfqMxSUeFySjCcRUA-1; Tue, 25 Nov 2025 08:23:27 -0500 X-MC-Unique: I6dymSfqMxSUeFySjCcRUA-1 X-Mimecast-MFC-AGG-ID: I6dymSfqMxSUeFySjCcRUA_1764077006 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 53BEE180034F; Tue, 25 Nov 2025 13:23:25 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.80]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E8697180049F; Tue, 25 Nov 2025 13:23:22 +0000 (UTC) Date: Tue, 25 Nov 2025 13:23:19 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Maydell Cc: Moritz Haase , qemu-devel@nongnu.org, petrosagg@resin.io, nghiant2710@gmail.com, forumi0721@gmail.com, laurent@vivier.eu Subject: Re: [PATCH] linux-user: add option to intercept execve() syscalls Message-ID: References: <20251125103859.1449760-1-Moritz.Haase@bmw.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.152, 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_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 Tue, Nov 25, 2025 at 01:14:23PM +0000, Peter Maydell wrote: > On Tue, 25 Nov 2025 at 12:20, Daniel P. Berrangé wrote: > > > > On Tue, Nov 25, 2025 at 11:38:59AM +0100, Moritz Haase wrote: > > > + if (i_arg) { > > > + new_argv = g_alloca(sizeof(void *)); > > > + new_argv[0] = i_arg; > > > > FYI, use of g_alloca() is no longer permitted in QEMU code. > > > > I thought we blocked that with -Walloca, but it seems we do not. > > We ought to fix that gap. > > We don't because we haven't yet eradicated all existing uses > of alloca type functions. We did that for the system emulation > code, but didn't find a way to add the -Walloca warning only > for the non-linux-user code: > > https://lore.kernel.org/qemu-devel/20250901132626.28639-1-philmd@linaro.org/ > > There are still a handful of alloca() calls in linux-user/ > and bsd-user/ which ideally we would convert but which haven't > been very high priority to clean up (because a linux user > guest can scribble all over QEMU memory anyway if it likes, > so being able to overrun the stack by passing a large value > into an alloca size doesn't let it do anything it couldn't > do by other means). I think we can fix that with a pragma. eg Add -Walloca to meson.build for everything, then add _Pragma("GCC diagnostic ignored -Walloca") to only linux-user/syscall.c and bsd-user/os-syscall.c files. 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 :|