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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 78669C433DF for ; Fri, 5 Jun 2020 16:11:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 459142077D for ; Fri, 5 Jun 2020 16:11:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591373484; bh=NZnV11U8sQBzLsjL+Ih82Hj1FQcrfTDZO6BsJVQT/T4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Bw3jqzrmuVmE8MtYUoNKrt0+yR2j5EjjaHcEwKv57LUCqHjbRcbptd2Gx0MmHQvn3 rMIGTFXD/j7/oZBmWhqOLWzat01hpk2Yuj9u29xHSDNLJTJSiY7bOxtozKHiWXqKSm CiM3vQQKMl7RpPNExq4RaNBLbbB1mrTumSDVKh+0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726083AbgFEQLX (ORCPT ); Fri, 5 Jun 2020 12:11:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:53334 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725944AbgFEQLW (ORCPT ); Fri, 5 Jun 2020 12:11:22 -0400 Received: from sol.localdomain (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5C59C206DB; Fri, 5 Jun 2020 16:11:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591373482; bh=NZnV11U8sQBzLsjL+Ih82Hj1FQcrfTDZO6BsJVQT/T4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JX4sH+Kl1LUL+oFflby7emnQQW7r38BOfqmaJL7kOaC2ZYQl9dDsN8hWxk8nK44QZ 7wTlwJ94E/+HCpHCKV6XJmX9tF1RM/d2fbeZF3S/WSY3Blo69Gn9hJXf3YNBCOSG+P hafDk7AEz42wn331P0PxE0rD0m3c4FyqQBkVEa0o= Date: Fri, 5 Jun 2020 09:11:21 -0700 From: Eric Biggers To: Matthew Wilcox Cc: syzbot , bjorn.andersson@linaro.org, davem@davemloft.net, kuba@kernel.org, linux-kernel@vger.kernel.org, manivannan.sadhasivam@linaro.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: BUG: using smp_processor_id() in preemptible code in radix_tree_node_alloc Message-ID: <20200605161121.GC1373@sol.localdomain> References: <000000000000a363b205a74ca6a2@google.com> <20200605035555.GA2667@sol.localdomain> <20200605112922.GB19604@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200605112922.GB19604@bombadil.infradead.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 05, 2020 at 04:29:22AM -0700, Matthew Wilcox wrote: > On Thu, Jun 04, 2020 at 08:55:55PM -0700, Eric Biggers wrote: > > Possibly a bug in lib/radix-tree.c? this_cpu_ptr() in radix_tree_node_alloc() > > can be reached without a prior preempt_disable(). Or is the caller of > > idr_alloc() doing something wrong? > > Yes, the idr_alloc() call is plainly wrong: > > mutex_lock(&qrtr_port_lock); > if (!*port) { > rc = idr_alloc(&qrtr_ports, ipc, > QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET + 1, > GFP_ATOMIC); > > If we can take a mutex lock, there's no excuse to be using GFP_ATOMIC. > That (and the call slightly lower in the function) should be GFP_KERNEL > as the minimal fix (below). I'll send a followup patch which converts > this IDR to the XArray instead. I did see that the GFP_ATOMIC was unnecessary, but it wasn't obvious to me that it was actually *wrong*. Shouldn't this requirement be documented for the @gfp argument to idr_alloc()? - Eric