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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id EA880C36008 for ; Tue, 25 Mar 2025 10:10:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 31F66280002; Tue, 25 Mar 2025 06:10:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2CED1280001; Tue, 25 Mar 2025 06:10:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1982C280002; Tue, 25 Mar 2025 06:10:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id F1602280001 for ; Tue, 25 Mar 2025 06:10:20 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id C2525598E1 for ; Tue, 25 Mar 2025 10:10:21 +0000 (UTC) X-FDA: 83259653442.11.A45B5F1 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf02.hostedemail.com (Postfix) with ESMTP id 9742A80009 for ; Tue, 25 Mar 2025 10:10:19 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=jITmb274; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf02.hostedemail.com: domain of oleg@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=oleg@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1742897419; a=rsa-sha256; cv=none; b=hoR/4OXa0YnyfDSZm7NAABU5PLo+gKEgFTtHEbeFk4lTTm1vvs1kvJ0Q/asV9xhtSlsT/H YqXFETeiWZoGAiAMPTxh2a9/kgzHkF8HuABGncg9nephz79RdfXChPkIQMjrIR2L9vAH1f Df/GxK2WkZqZoLbGTN3gknvKRpY2Ucg= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=jITmb274; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf02.hostedemail.com: domain of oleg@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=oleg@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1742897419; h=from:from:sender: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:dkim-signature; bh=+yHwlyVryiDRjhu9Lrq1vGrFAuzbF6NTK9Kgojwnnyo=; b=6LVme4VlUPHtXqwo7LzuMQP6uekixmALdOHVj5gp4x+ETQwaVp08lx+mLy/krdXDJe2yUq aV2nDKHacre9BIGxj/ie0OLslCntrQYwrNVtiCduAg9rjqvH5j9MhqVKSSmXgSVHAaTd7S uGTpAVShtkWqOdRLEY5EwAtUBI01suE= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1742897418; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+yHwlyVryiDRjhu9Lrq1vGrFAuzbF6NTK9Kgojwnnyo=; b=jITmb274d1QIJixU0BRi9+8C1wJWM21ddQghzTQk/F4KnoIlJPDDb3WxlEwvnCAWE+xoXx f/On5gYEEZ4lrabMVrErrzzZbuqau+PqIPEm8UlRypFM5fvydqaZgDQhePvuju4GaR6nXp NebCG8RqdAB9+YSMnvPwuiwxTcP5twM= 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-496-liIXkxccNoKKRN5ZT6cOSw-1; Tue, 25 Mar 2025 06:10:17 -0400 X-MC-Unique: liIXkxccNoKKRN5ZT6cOSw-1 X-Mimecast-MFC-AGG-ID: liIXkxccNoKKRN5ZT6cOSw_1742897415 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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 2C8D61801A06; Tue, 25 Mar 2025 10:10:15 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.42]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 4080D1956095; Tue, 25 Mar 2025 10:10:10 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 25 Mar 2025 11:09:42 +0100 (CET) Date: Tue, 25 Mar 2025 11:09:37 +0100 From: Oleg Nesterov To: Mateusz Guzik Cc: syzbot , brauner@kernel.org, kees@kernel.org, viro@zeniv.linux.org.uk, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH] exec: fix the racy usage of fs_struct->in_exec Message-ID: <20250325100936.GC29185@redhat.com> References: <67dc67f0.050a0220.25ae54.001f.GAE@google.com> <20250324160003.GA8878@redhat.com> <20250324182722.GA29185@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9742A80009 X-Stat-Signature: npdodtgf593okt7473iuyea7o36wkiao X-Rspam-User: X-HE-Tag: 1742897419-512442 X-HE-Meta: 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 Ufwk7dMH Dzyz298WLrx9tUZcimHgNYcq986Y0ZicpRR3En7M3Q+rP4VU1X5REh/aewRYYNMX669bWjRgNxevVq4cTCDF6NhuJG3PoRPlqeqIQzc3JQKDITObHe4W/kBzMoFF7QeGLdRsYsnNCF/ELBy0msl/e+Ri00o3dI9H9D0onkqnbUdBwcxK4vyKgUQYI3O4tjcO+HXAlP3FZpmSRT9L0yR0uFDoABDljXrP/Ot3/xKBncY+lZfvP2y4hOmI0tjXxvAPpJYt3pNNt8X4/00YSQv37POBxQfqdZzChkY2wDTGCe5SkJR9dXOLZoe7OKHKsS8TqGASo/0yoTVEMwjfazxYcFbmX7xd24vKJZt/jHE33/L/iZDiTmyX/GUg2lgliHySJUv71NQUDTBM7C4nZ/RVF4CEdEe29hc1wg8AuLPbKfX3bS7qv8e14u/0q/qXe8wiQfSQb X-Bogosity: Ham, tests=bogofilter, spamicity=0.009073, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/24, Mateusz Guzik wrote: > > On Mon, Mar 24, 2025 at 7:28 PM Oleg Nesterov wrote: > > > > So to me it would be better to have the trivial fix for stable, > > exactly because it is trivially backportable. Then cleanup/simplify > > this logic on top of it. > > So I got myself a crap testcase with a CLONE_FS'ed task which can > execve and sanity-checked that suid is indeed not honored as expected. So you mean my patch can't fix the problem? > Anyhow, the plan would be to serialize on the bit, synchronized with > the current spin lock. copy_fs would call a helper to wait for it to > clear, would still bump ->users under the spin lock. > > This would decouple the handling from cred_mutex and avoid weirdness > like clearing the ->in_exec flag when we never set it. I don't really understand the idea, but as I said I won't argue with another solution. Oleg.