svn commit: r232181 - in head/sys: kern sys

[Julian Elischer]

On 2/29/12 7:33 AM, Konstantin Belousov wrote:
> On Wed, Feb 29, 2012 at 09:36:02AM -0500, John Baldwin wrote:
>> On Wednesday, February 29, 2012 8:25:07 am Konstantin Belousov wrote:
>>> On Wed, Feb 29, 2012 at 02:37:25PM +0200, Mikolaj Golub wrote:
>>>> On Wed, 29 Feb 2012 12:03:00 +0000 Robert N. M. Watson wrote:
>>>>
>>>>   RNMW>  I think the monitoring aspect of the patch is fine.
>>>>
>>>>   RNMW>  The bit I was worried about was external umask changes. This can cause
>>>>   RNMW>  race conditions for applications that manage their umask -- for
>>>>   RNMW>  example, bsdtar, if I recall correctly. It's one thing to use a
>>>>   RNMW>  debugger to force an application to change its umask -- the developer
>>>>   RNMW>  needs to know they are changing application behaviour. But exposing a
>>>>   RNMW>  feature that can lead to correct applications but incorrect results is
>>>>   RNMW>  a risky thing to do, hence my objection.
>>>>
>>>>   RNMW>  I think given the other objections, it would be wise to remove write
>>>>   RNMW>  access to process umasks, but retain read access for procstat (which is
>>>>   RNMW>  quite useful, I agree).
>>>>
>>>> I still don't see why having a sysctl RW is worse than asking users to run
>>>> something like in the attach when they need to change umask for another
>>>> process, but ok, if people don't like RW I will remove it.
>>>>
>>> What is done is attach is much worse then the sysctl, just because
>>> debugger attach often causes spurious EINTR, indeed seriously disrupting
>>> applications, as opposed to some uncertain damage that could be done in
>>> theory.
>> kgdb doesn't though, and presumably for umask you would change it via kgdb, so
>> from the running process' perspective it would look the same as changing it via
>> sysctl.
> Right, but an idea of the change was to allow to do this for somebody who
> does not know how to perform it in kgdb. Not to mention that kgdb -w
> is risky, e.g. because filedesc might have changed under kgdb, so you would
> write over freed memory.

but it's lowering the bar TOO much I think,