linux-kernel - Re: [PATCH v8 1/5] ipc: IPCMNI limit check for msgmni and shmmni

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Date:   Fri, 17 Aug 2018 09:51:09 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Waiman Long <longman@...hat.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Takashi Iwai <tiwai@...e.de>, Davidlohr Bueso <dbueso@...e.de>,
        manfred@...orfullife.com
Subject: Re: [PATCH v8 1/5] ipc: IPCMNI limit check for msgmni and shmmni

On Mon, 18 Jun 2018, 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 <longman@...hat.com>

Reviewed-by: Davidlohr Bueso <dave@...olabs.net>

>---
> 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
>