From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753465AbeEGX5P (ORCPT ); Mon, 7 May 2018 19:57:15 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50280 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752920AbeEGX5N (ORCPT ); Mon, 7 May 2018 19:57:13 -0400 Subject: Re: [PATCH v7 1/4] ipc: IPCMNI limit check for msgmni and shmmni To: "Luis R. Rodriguez" Cc: Kees Cook , Andrew Morton , Jonathan Corbet , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Al Viro , Matthew Wilcox , "Eric W. Biederman" References: <1525726752-29281-1-git-send-email-longman@redhat.com> <1525726752-29281-2-git-send-email-longman@redhat.com> <20180507223910.GW27853@wotan.suse.de> From: Waiman Long Organization: Red Hat Message-ID: Date: Mon, 7 May 2018 19:57:12 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180507223910.GW27853@wotan.suse.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/07/2018 06:39 PM, Luis R. Rodriguez wrote: > On Mon, May 07, 2018 at 04:59:09PM -0400, Waiman Long wrote: >> A user can write arbitrary integer values to msgmni and shmmni sysctl >> parameters without getting error, but the actual limit is really >> IPCMNI (32k). This can mislead users as they think they can get a >> value that is not real. >> >> The right limits are now set for msgmni and shmmni so that the users >> will become aware if they set a value outside of the acceptable range. >> >> Signed-off-by: Waiman Long >> --- >> ipc/ipc_sysctl.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c >> index 8ad93c2..f87cb29 100644 >> --- a/ipc/ipc_sysctl.c >> +++ b/ipc/ipc_sysctl.c >> @@ -99,6 +99,7 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write, >> static int zero; >> static int one = 1; >> static int int_max = INT_MAX; >> +static int ipc_mni = IPCMNI; >> >> static struct ctl_table ipc_kern_table[] = { >> { >> @@ -120,7 +121,9 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write, >> .data = &init_ipc_ns.shm_ctlmni, >> .maxlen = sizeof(init_ipc_ns.shm_ctlmni), >> .mode = 0644, >> - .proc_handler = proc_ipc_dointvec, >> + .proc_handler = proc_ipc_dointvec_minmax, >> + .extra1 = &zero, >> + .extra2 = &ipc_mni, >> }, >> { >> .procname = "shm_rmid_forced", >> @@ -147,7 +150,7 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write, >> .mode = 0644, >> .proc_handler = proc_ipc_dointvec_minmax, >> .extra1 = &zero, >> - .extra2 = &int_max, >> + .extra2 = &ipc_mni, >> }, >> { >> .procname = "auto_msgmni", >> -- >> 1.8.3.1 > It seems negative values are not allowed, if true then having > a caller to use proc_douintvec_minmax() would help with ensuring > no invalid negative input values are used as well. > > Luis Negative value doesn't mean sense here. So it is true that we can use proc_douintvec_minmax() instead. However, the data types themselves are defined as "int". So I think it is better to keep using proc_dointvec_minmax() to be consistent with the data type. Cheers, Longman