From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752575AbeCMSSN (ORCPT ); Tue, 13 Mar 2018 14:18:13 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:54219 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751806AbeCMSSL (ORCPT ); Tue, 13 Mar 2018 14:18:11 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Waiman Long Cc: "Luis R. Rodriguez" , Kees Cook , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Al Viro , Matthew Wilcox References: <1520885744-1546-1-git-send-email-longman@redhat.com> <1520885744-1546-5-git-send-email-longman@redhat.com> Date: Tue, 13 Mar 2018 13:17:24 -0500 In-Reply-To: <1520885744-1546-5-git-send-email-longman@redhat.com> (Waiman Long's message of "Mon, 12 Mar 2018 16:15:42 -0400") Message-ID: <87woyfyh57.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1evoV0-000744-AL;;;mid=<87woyfyh57.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=174.19.85.160;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18Z3h07KzWNo676YgUpyelNMkFe4GKA+xc= X-SA-Exim-Connect-IP: 174.19.85.160 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 TVD_RCVD_IP Message was received from an IP address * 0.7 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa04 1397; Body=1 Fuz1=1 Fuz2=1] X-Spam-DCC: XMission; sa04 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Waiman Long X-Spam-Relay-Country: X-Spam-Timing: total 184 ms - load_scoreonly_sql: 0.05 (0.0%), signal_user_changed: 2.7 (1.5%), b_tie_ro: 1.96 (1.1%), parse: 0.74 (0.4%), extract_message_metadata: 2.8 (1.5%), get_uri_detail_list: 1.24 (0.7%), tests_pri_-1000: 3.3 (1.8%), tests_pri_-950: 1.02 (0.6%), tests_pri_-900: 0.82 (0.4%), tests_pri_-400: 19 (10.5%), check_bayes: 18 (10.0%), b_tokenize: 6 (3.0%), b_tok_get_all: 6 (3.1%), b_comp_prob: 1.87 (1.0%), b_tok_touch_all: 2.7 (1.5%), b_finish: 0.66 (0.4%), tests_pri_0: 144 (78.0%), check_dkim_signature: 0.50 (0.3%), check_dkim_adsp: 2.8 (1.5%), tests_pri_500: 3.2 (1.7%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH v4 4/6] ipc: Clamp msgmni and shmmni to the real IPCMNI limit X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Waiman Long writes: > 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. > > Enforcing the limit by failing the sysctl parameter write, however, > can break existing user applications. Which applications examples please. I am seeing this patchset late but it looks like a whole lot of changes to avoid a theoretical possibility. Changes that have an impact on more than just the ipc code you are patching. That makes me feel very uncomfortable with these changes. Eric > Instead, the range clamping flag > is set to enforce the limit without failing existing user code. Users > can easily figure out if the sysctl parameter value is out of range > by either reading back the parameter value or checking the kernel > ring buffer for warning. > > Signed-off-by: Waiman Long > --- > ipc/ipc_sysctl.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c > index 8ad93c2..1955dd4 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 +121,10 @@ 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, > + .flags = CTL_FLAGS_CLAMP_RANGE, > }, > { > .procname = "shm_rmid_forced", > @@ -147,7 +151,8 @@ 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, > + .flags = CTL_FLAGS_CLAMP_RANGE, > }, > { > .procname = "auto_msgmni",