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From: (Eric W. Biederman)
To: Waiman Long <>
Cc: "Luis R. Rodriguez" <>,
	Kees Cook <>,
	Andrew Morton <>,
	Jonathan Corbet <>,,,, Al Viro <>,
	Matthew Wilcox <>
Subject: Re: [PATCH v6 0/8] ipc: Clamp *mni to the real IPCMNI limit & increase that limit
Date: Tue, 01 May 2018 21:18:17 -0500	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <> (Waiman Long's message of "Fri, 27 Apr 2018 17:00:30 -0400")

> The sysctl parameters msgmni, shmmni and semmni have an inherent limit
> of IPC_MNI (32k). However, users may not be aware of that because they
> can write a value much higher than that without getting any error or
> notification. Reading the parameters back will show the newly written
> values which are not real.
> Enforcing the limit by failing sysctl parameter write, however, may
> cause regressions if existing user setup scripts set those parameters
> above 32k as those scripts will now fail in this case.

I have a serious problem with this approach.  Have you made any effort
to identify any code that sets these values above 32k?  Have you looked
to see if these applications actually care if you return an error when
a value is set too large?

Right now this seems like a lot of work to avoid breaking applications
and or users that may or may not exist.  If you can find something that
will care sure.  We need to avoid breaking userspace and causing
regressions.  However as this stands it looks you are making maintenance
of the kernel more difficult to avoid having to look to see if there are
monsters under the bed.


  parent reply	other threads:[~2018-05-02  2:18 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 21:00 Waiman Long
2018-04-27 21:00 ` [PATCH v6 1/8] sysctl: Add flags to support min/max range clamping Waiman Long
2018-04-27 21:00 ` [PATCH v6 2/8] proc/sysctl: Provide additional ctl_table.flags checks Waiman Long
2018-04-27 21:00 ` [PATCH v6 3/8] sysctl: Warn when a clamped sysctl parameter is set out of range Waiman Long
2018-04-30 22:40   ` Kees Cook
2018-05-01 13:41     ` Waiman Long
2018-04-27 21:00 ` [PATCH v6 4/8] ipc: Clamp msgmni and shmmni to the real IPCMNI limit Waiman Long
2018-04-27 21:00 ` [PATCH v6 5/8] ipc: Clamp semmni " Waiman Long
2018-04-27 21:00 ` [PATCH v6 6/8] test_sysctl: Add range clamping test Waiman Long
2018-04-27 21:00 ` [PATCH v6 7/8] ipc: Allow boot time extension of IPCMNI from 32k to 2M Waiman Long
2018-04-29 15:54   ` kbuild test robot
2018-04-27 21:00 ` [PATCH v6 8/8] ipc: Conserve sequence numbers in extended IPCMNI mode Waiman Long
2018-04-29 16:51   ` kbuild test robot
2018-05-02  2:18 ` Eric W. Biederman [this message]
2018-05-02 13:23   ` [PATCH v6 0/8] ipc: Clamp *mni to the real IPCMNI limit & increase that limit Waiman Long
2018-05-02 15:06     ` Eric W. Biederman
2018-05-07 19:14       ` Waiman Long

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