Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752618AbdHCMDT (ORCPT ); Thu, 3 Aug 2017 08:03:19 -0400 Received: from mail-lf0-f42.google.com ([209.85.215.42]:35015 "EHLO mail-lf0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752098AbdHCMDR (ORCPT ); Thu, 3 Aug 2017 08:03:17 -0400 Subject: Re: [PATCH] hysdn: fix to a race condition in put_log_buffer To: Anton Volkov , isdn@linux-pingi.de Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org, khoroshilov@ispras.ru References: <2f35ddaf-88d9-e848-f83b-3001b36b2883@linux-pingi.de> <1501760001-22193-1-git-send-email-avolkov@ispras.ru> From: Sergei Shtylyov Organization: Cogent Embedded Message-ID: Date: Thu, 3 Aug 2017 15:03:13 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <1501760001-22193-1-git-send-email-avolkov@ispras.ru> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-MW Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1780 Lines: 57 Hello! On 08/03/2017 02:33 PM, Anton Volkov wrote: > The synchronization type that was used earlier to guard the loop that > deletes unused log buffers may lead to a situation that prevents any > thread from going through the loop. > > The patch deletes previously used synchronization mechanism and moves > the loop under the spin_lock so the similar cases won't be feasible in > the future. > > Found by by Linux Driver Verification project (linuxtesting.org). > > Signed-off-by: Anton Volkov > --- > drivers/isdn/hysdn/hysdn_proclog.c | 27 ++++++++++++--------------- > 1 file changed, 12 insertions(+), 15 deletions(-) > > diff --git a/drivers/isdn/hysdn/hysdn_proclog.c b/drivers/isdn/hysdn/hysdn_proclog.c > index 7b5fd8f..b152c6c 100644 > --- a/drivers/isdn/hysdn/hysdn_proclog.c > +++ b/drivers/isdn/hysdn/hysdn_proclog.c [...] > else > pd->log_tail->next = ib; /* follows existing messages */ > pd->log_tail = ib; /* new tail */ > - i = pd->del_lock++; /* get lock state */ > - spin_unlock_irqrestore(&card->hysdn_lock, flags); > > /* delete old entrys */ > - if (!i) > - while (pd->log_head->next) { > - if ((pd->log_head->usage_cnt <= 0) && > - (pd->log_head->next->usage_cnt <= 0)) { > - ib = pd->log_head; > - pd->log_head = pd->log_head->next; > - kfree(ib); > - } else > - break; > - } /* pd->log_head->next */ > - pd->del_lock--; /* release lock level */ > + while (pd->log_head->next) { > + if ((pd->log_head->usage_cnt <= 0) && > + (pd->log_head->next->usage_cnt <= 0)) { > + ib = pd->log_head; > + pd->log_head = pd->log_head->next; > + kfree(ib); > + } else > + break; > + } /* pd->log_head->next */ Need {} in the *else* branch as *if* had them. [...] MBR, Sergei