From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA48531ED7F for ; Wed, 7 Jan 2026 09:43:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767779012; cv=none; b=HmxWZm/G2K6Kh16gdBh3jXkrCTXDoXKnzVPfKeKAowgiU80RMziLaf5ezIXLW+5QCQ5s8e/6E6Nx+WnOU+5dsQvN8ByWvEc8fNkPrHVKJ3Mh7CkWhHreqGYBpMQvvfLwljbSbxMNWgMiVSm6Wk56rQ1jUGYe8emH2JkZ6/Ye36U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767779012; c=relaxed/simple; bh=7SeG9KGb8WmEzZvBH9dmoHkuFyxB6GVa2xVg46m3R0M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QNkSk/j5pWFGi5/j6X3OnFByBMlzMoAZVv1AUpBg0TuOlQvyO60BHPqAjhwtlph5lo/g7HEO53EbNPwL3GPz21hh6biJZBi+nNWAyEHL5+0hFVDAMTHPF+K+chrpur/JByKvxFzahiscGRlq/oYEuCFp66HynyHLKAchmp6pTIc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=c+ZcZbWa; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="c+ZcZbWa" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1767779009; 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=7SeG9KGb8WmEzZvBH9dmoHkuFyxB6GVa2xVg46m3R0M=; b=c+ZcZbWauMvJaqRJwBXF5wBZ/U8Z5N5XWiUVIvT8Hjqx5A6C8KA5xA0k0SIZU+gk+JtzEi cH3mRTBSTtgi0QvZPWLEo2mFu5qdZq9mRyaSBxmA882CimtmSfEnsFsThep5CQuWIdSLME zSAOFt0FCHLLEVHhYakD7Cc3JKAqiKs= 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-543---AkOO61MOSGlN5yPCRLzw-1; Wed, 07 Jan 2026 04:43:26 -0500 X-MC-Unique: --AkOO61MOSGlN5yPCRLzw-1 X-Mimecast-MFC-AGG-ID: --AkOO61MOSGlN5yPCRLzw_1767779003 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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 1B34C1800626; Wed, 7 Jan 2026 09:43:23 +0000 (UTC) Received: from fedora (unknown [10.45.226.75]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 24FC618008FF; Wed, 7 Jan 2026 09:43:15 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 7 Jan 2026 10:43:24 +0100 (CET) Date: Wed, 7 Jan 2026 10:43:16 +0100 From: Oleg Nesterov To: Qing Wang Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, david@kernel.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, brauner@kernel.org, mjguzik@gmail.com, jack@suse.cz, joel.granados@kernel.org, linux-kernel@vger.kernel.org, syzbot+e0378d4f4fe57aa2bdd0@syzkaller.appspotmail.com Subject: Re: [PATCH] fork/pid: Fix use-after-free in __task_pid_nr_ns Message-ID: References: <20260105043627.1758935-1-wangqing7171@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On 01/06, Oleg Nesterov wrote: > > On a second thought... > > sched_fork() is called before perf_event_init_task(). So perhaps > sync_child_event() could also check task->__state != TASK_NEW before > perf_event_read_event() ? > > Not sure, I know nothing about perf. Would be nice if perf experts can > take a look. Or something else, but we can't rely on pid_alive() or ->signal != NULL checks. perf_event_init_task() is called soon after dup_task_struct(), so pid_alive() is true and child->signal == current->signal. Lets forget about use-after-free. What if perf_child_detach() paths call __task_pid_nr_ns() before copy_signal/etc ? In this case perf_event_pid/perf_event_tid will return the pids of the forking process, not the child's pids. Oleg.