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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B4B0CFEDA0F for ; Tue, 17 Mar 2026 19:08:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BDFF36B0096; Tue, 17 Mar 2026 15:08:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B90B06B0098; Tue, 17 Mar 2026 15:08:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AA66C6B0099; Tue, 17 Mar 2026 15:08:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 988636B0096 for ; Tue, 17 Mar 2026 15:08:25 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 1CE4C571A7 for ; Tue, 17 Mar 2026 19:08:25 +0000 (UTC) X-FDA: 84556490970.05.9C15140 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf13.hostedemail.com (Postfix) with ESMTP id DE3A820011 for ; Tue, 17 Mar 2026 19:08:22 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ZowhB4Yb; spf=pass (imf13.hostedemail.com: domain of oleg@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1773774503; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=9cMncruhV3zGKox3/ctrnX7MA7dyJ750pVWwUyV32A0=; b=YDeDXQBwDWUkRwib3beK3famoEqz801QByFBandHS4xw4/pjbGo8ohypXY+tNa3C8TaKe4 ylBeVvbWlYp2as7VkzbPqOdOc6i7XTI/nA6EBbKljVNwX9rPFRttL2br7g4+aGZrOF+D9/ xd+2QWnEHpJ+A2GYYu8XYXD5TvSU37s= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ZowhB4Yb; spf=pass (imf13.hostedemail.com: domain of oleg@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773774503; a=rsa-sha256; cv=none; b=zcQDzOJm7bvVqCArARQCy13A183cePmGUPgFFNHK1gZVG8HIrwxvr2i5pa32q4JTFeSKfQ yjF4sw2R/4HNSWPiMnZ2CdexsijRi34LQNK3FNgAHTzYNhbciwYiURk7Juhrkb617mRzua p2J+V73x/zpaObEynGnE+RV5O+R7ix8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1773774502; 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=9cMncruhV3zGKox3/ctrnX7MA7dyJ750pVWwUyV32A0=; b=ZowhB4YbTTdF8rV+ziUMo6dxTMvMA6zLMfBRwp5zpYse0ZejYk3JFV79PLHYBaMYrbJYMh C5uIeBAaqPBQAqLmh2VyznZx61Dola0POd3JThA3bDHL+LaT5zdKdqtYDxGzeXhANgn9ws xo1ps0UIDiDHexdhshVDnrzmjpZXpeQ= 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-183-eCvhrhSaO-murqpA7XqfXg-1; Tue, 17 Mar 2026 15:08:18 -0400 X-MC-Unique: eCvhrhSaO-murqpA7XqfXg-1 X-Mimecast-MFC-AGG-ID: eCvhrhSaO-murqpA7XqfXg_1773774497 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 6E4BC1800245; Tue, 17 Mar 2026 19:08:17 +0000 (UTC) Received: from fedora (unknown [10.45.225.204]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 9EEEC30001A1; Tue, 17 Mar 2026 19:08:15 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 17 Mar 2026 20:08:17 +0100 (CET) Date: Tue, 17 Mar 2026 20:08:14 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Deepanshu Kartikey , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH -mm v2] do_notify_parent: sanitize the valid_signal() checks Message-ID: References: <20260316151956.563558-1-kartikey406@gmail.com> <20260317113452.cede9a514dfed36a1cb0e5a9@linux-foundation.org> MIME-Version: 1.0 In-Reply-To: <20260317113452.cede9a514dfed36a1cb0e5a9@linux-foundation.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: a2xWOlorrVdZgsYviiGMtRJ3yYPZjWNOwAmkN2KTyhM_1773774497 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Rspamd-Queue-Id: DE3A820011 X-Rspamd-Server: rspam08 X-Stat-Signature: kfgyxibxu36p37f7mrrckz7ox496mwxj X-HE-Tag: 1773774502-77199 X-HE-Meta: U2FsdGVkX1/+J19zrcGYbw9VX6RdglftvVnhnIYHdktQCD4qeEVgencEufKPD1M6G+Z+eQgJgYItudAwE07zY4Mdk1MXAwo8OcuKacKW4+4sNJmUIqVOb5GKo+qWZ0yw5X1BFDuFNpkqPlAjZO6MlIsfJIRs14jPtT3Sq7Rs6o9mlL35r5aB6l5fwcU11MLEIZ6aDn6xit1OoI1YnB5AzyZIIdpOiTmSSeb6j1Kk1L5v0FZl2+pk/LnKSGiUy1hPcjfnVw+wEbp6eXmKhgeplDyyuO4BOr+ACtDKuDcKmZh19Qb7YtS4eEeAeY9ZKhDiZFAbuwC5c6aTyGA197bKSCJQQhPSuUBt1NHKaJHIht4VQzH1Pjn0dH48Anrgko5TRSIm+FCQaYgs0H9DSA4ysl64bf1UkpY5jYaigclucZrMaOM3Ae8AS7W3+VIov8dlkM1O+0NFwmqCMXAZ94sBi7pahFN8fDYG7d3x+od/YzItCYY24BNpgFItgRYg2xyRRg9k3iHsZy5WQYSFKhMJpRMSLxQ4UAQP4TnhuxOv8mquZBpOjg8z+sOALOHBMjPky8Hg5+qVylHE968xYIoTirc1sB452pESsyO9JmlrzHianHkEBBkJXzshVExoYM67h07txzwSyCy5zoqsf6s+LscSYhSkjU0Q3Gma4RWKp9e+4CD5gj4XF7foe++Qiyv8NjjXB9I+ml950pYoDwOimajS5FDWJ1Uw428TBzOzbZX+zBw9Kwa8G9mCa6+LrikCx8wwu5eMd7UPVCsZoYiHlrqyIBml5q6IJFvYvjbOyBeYVjS2HJta2pn/9iQAeuWk6jA5U70YgVM16E7JXB2+R3uGXPaArFlBOzbKc3S26kk0AnIOVNj/LQVlQbE8kkiLCj9+lzadlBoUcUTFeeU5esSNf5tS9IsJCUkWK6EUU85EjlvpWfaFwn81fzG7338H9G527NbXB2WtZnnB31t J17mXa90 14Uz0IdkEUHbH1z9nbm6fyTwC68eLcHeLgTTJ8zvgYctRSWyV69YhhRf04LJe8MrknJ2F3yfovxzlDlckGb6rofqvevQrPxecXBZt3I5UO/Ed+bzaUzybnq1VRyR+Orijjr0MMldPCqC1nh0hpzzJzT+C4MQpnaca8ZIuVdRkWFOqGQHv+gJoNR1H4x6kyRffZdjIpSHBL5vgrmoqrkucN4mvlM/AN4HBHdC10VUPMgFMt7txdJcn7S2lpgIijyeOysuKeEo5g/4YbSLkuOslLg8tv1eAAAvOJypl4fdTsgeT+DQMsuCHvTvsfda9MjMvH0/touj4ZFsV8k2Zb7K8USl5TKOzddkEM+9X2M6YAZCyFZvaMtPlYg1UDD3Vqasy011D0Iwm+884CE6LGiWU/FW0P7+OWjgwN7DzqO5LFpWG8bNys52DseAGG1+pjcZ5KdXq4nnSZfm0hv5+lAQBvobMh3Cls57AvBtH Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/17, Andrew Morton wrote: > > On Tue, 17 Mar 2026 14:58:18 +0100 Oleg Nesterov wrote: > > > Now that kernel_clone() checks valid_signal(args->exit_signal), the "sig" > > argument of do_notify_parent() must always be valid or we have a bug. > > > > However, do_notify_parent() only checks that sig != -1 at the start, then > > it does another valid_signal() check before __send_signal_locked(). > > > > This is confusing. Change do_notify_parent() to WARN and return early if > > valid_signal(sig) is false. > > Sashiko has a question: > https://sashiko.dev/#/patchset/abld-ilvMEZ7VgMw%40redhat.com I think that userpace can't bypass kernel_clone() (which checks valid_signal) before copy_process(). This includes ia32_clone() and sparc_clone() mentioned in the link above. There are in-kernel users (fork_idle, create_io_thread, vhost_task_create). But if they pass a non-valid exit_signal (they don't), we do have a kernel bug and WARN_ON() added by this patch should catch the problem. In short. From the link above: While kernel_clone() expects the caller to validate args->exit_signal this was true before kernel-fork-validate-exit_signal-in-kernel_clone.patch from Deepanshu, and my cleanup depends on it. Oleg.