From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 437DF3254B8 for ; Tue, 6 Jan 2026 11:20:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767698409; cv=none; b=Qqnpjv3jUD8laUfSJxJBv6Vw//fQigCcAUm+/SUrbZPn9Nopdfpc21c6yA9OX15o0ehZaeyEI2AaJDfCk0/otlSg1C1jgWuLIb4dNvnNPNcE/F26yZyb69CDXsLcFK6llqt8/Q9MTR+/Df/PHEfHLHyv2IZR12sxpbzN3rFpc5c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767698409; c=relaxed/simple; bh=VaLYxpSzekTYGDkruC3OXUK8vYm9dztYBNvNt8Qo13U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZLHuhrbtttylucw5X4vbB1vzS3pm3Ca2i1QoOeqjufVNz+87vKAuEh08Bk6W0X8EGBdkzbGPUcpMzgZdPLO9j7Lcs8HKtIOZhgeTXCUP34eems91xmJH6x+tkITsAsdesGAvdW6TptfZlLzCgQbC5MBhQlEJ0Sq7UKDkumEcJ5o= 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=D3mmTdr0; arc=none smtp.client-ip=170.10.133.124 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="D3mmTdr0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1767698405; 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=QMCZauFVNMlWfleYcwiVMISP1sYawf0Obx5j/gDPROI=; b=D3mmTdr00OBB2g5dsQ44ZE3m4EcfLyi936OMELHCyYr0scyltJeAK92d0OMDVvlu9gW5VT M3WT8Tq8oZXSFrDbICY/cOVRS8kiegvEbGR4LTH9nCnJ/ixkJ2bMyYuSXhpPsybdDpEN1g szJcqPMJe5R4u5DP34p289cY1UoE3Vc= 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-586-_2M5bgUHOkCOcK3kHQg-3w-1; Tue, 06 Jan 2026 06:20:01 -0500 X-MC-Unique: _2M5bgUHOkCOcK3kHQg-3w-1 X-Mimecast-MFC-AGG-ID: _2M5bgUHOkCOcK3kHQg-3w_1767698399 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 F1460180028B; Tue, 6 Jan 2026 11:19:58 +0000 (UTC) Received: from fedora (unknown [10.44.33.62]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 3E2AB19560A7; Tue, 6 Jan 2026 11:19:49 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 6 Jan 2026 12:19:58 +0100 (CET) Date: Tue, 6 Jan 2026 12:19:48 +0100 From: Oleg Nesterov To: Qing Wang Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, brauner@kernel.org, bsegall@google.com, david@kernel.org, dietmar.eggemann@arm.com, jack@suse.cz, joel.granados@kernel.org, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, mjguzik@gmail.com, peterz@infradead.org, rostedt@goodmis.org, rppt@kernel.org, syzbot+e0378d4f4fe57aa2bdd0@syzkaller.appspotmail.com, vbabka@suse.cz, vincent.guittot@linaro.org Subject: Re: [PATCH] fork/pid: Fix use-after-free in __task_pid_nr_ns Message-ID: References: <20260106105832.2779312-1-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: <20260106105832.2779312-1-wangqing7171@gmail.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On 01/06, Qing Wang wrote: > > Could we put the checking 'pid_alive(task)' into __task_pid_nr_ns()? I don't think so... see below. > Because there is another similar use case here. > > > arch/s390/kernel/perf_cpum_sf.c > 619,9: pid = __task_pid_nr_ns(tsk, type, event->ns); This case is not similar. This tsk was found by find_task_by_pid_ns(), it must be fully initialized. So I don't think it makes sense to add the additional check into __task_pid_nr_ns(). > --- a/kernel/pid.c > +++ b/kernel/pid.c > @@ -515,7 +515,7 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, > rcu_read_lock(); > if (!ns) > ns = task_active_pid_ns(current); > - if (ns) > + if (ns && pid_alive(task)) This reminds me... the 2nd "if (ns) check must die. I'll ping Cristian. See https://lore.kernel.org/all/20251015123613.GA9456@redhat.com/ Oleg.