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 ED59B45025 for ; Thu, 28 Nov 2024 08:08:46 +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=1732781328; cv=none; b=uqiDqTDJ2X+ben9+Uoz7Y3vQXfOOVY5CBCHJAcqWqJFkmlp2uCrQz+NU31RshJV0YhTLbxsoKrRcjp97vPYGDs/7UyR2lJG/KqQxLdFkFigACJveLiDuuN0RyAK4CBps4WFY1nRwb6SERaa3qweppJJc1v5Ei1W9uSlj0lvtbxQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732781328; c=relaxed/simple; bh=4srSRusTbIfBMVE+olmx0QPHrbQqHJUCthbkmng4gck=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gas5YNeDLU5dzdKNdUMseHbTWzm3oD9hOphZkAcel1yjDJ9Lx3sZBfQGa8AwT/k1hLwg6ZOiFVBnPpLcJMNMGQGLz7T1Q9aWC7AjLu8n74d0cwE7VUHdBe7r5EDqheW3a6HfCXZJP5odkr5CrtkbcfFGH7ME7ZsRlDkvMepFx9Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=AjKCfrD6; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="AjKCfrD6" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1732781326; 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=4srSRusTbIfBMVE+olmx0QPHrbQqHJUCthbkmng4gck=; b=AjKCfrD6G6OhZNn5kuQXcLbotSiTRXmlYsVLLEVMF7TwrQdp/vh5Sn09VeR9ligY8vZHry j6ZvvnGRtgWehO5Cczb1ZFdmnXWSVmESLytkFYBczROfo0QAAlbjihXQdMq/snbqH7hjZJ 5781IsHvRddQ7pSxsKSfqRrl9IHnZOk= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-528-Xz53NpUnPR6VcAlAbiZ5hQ-1; Thu, 28 Nov 2024 03:08:39 -0500 X-MC-Unique: Xz53NpUnPR6VcAlAbiZ5hQ-1 X-Mimecast-MFC-AGG-ID: Xz53NpUnPR6VcAlAbiZ5hQ 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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 946211955F3C; Thu, 28 Nov 2024 08:08:37 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.112]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id D1604300018D; Thu, 28 Nov 2024 08:08:33 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 28 Nov 2024 09:08:16 +0100 (CET) Date: Thu, 28 Nov 2024 09:08:11 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Zhen Ni , viro@zeniv.linux.org.uk, catalin.marinas@arm.com, brauner@kernel.org, zev@bewilderbeest.net, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH] kernel/sys: Optimize do_prlimit lock scope to reduce contention Message-ID: <20241128080811.GC10998@redhat.com> References: <20241120132156.207250-1-zhen.ni@easystack.cn> <20241127174536.752def18058e84487ab9ad65@linux-foundation.org> <20241128071351.GA10998@redhat.com> <20241128073911.GB10998@redhat.com> Precedence: bulk X-Mailing-List: linux-security-module@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: <20241128073911.GB10998@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On 11/28, Oleg Nesterov wrote: > > On 11/28, Oleg Nesterov wrote: > > > > The problem is that task_lock(tsk->group_leader) doesn't look right with or > > without this patch. I'll try to make a fix on weekend. > > > > If the caller is sys_prlimit64() and tsk != current, then ->group_leader is > > not stable, do_prlimit() can race with mt exec and take the wrong lock. > > ... and task_unlock(tsk->group_leader) is simply unsafe. > > perhaps something like below, No, this is wrong too, > I'll try to think more. Yes... Oleg.