Re: [RFC 06/19] ktf: A simple debugfs interface to test results

[Greg Kroah-Hartman]

On Thu, Aug 15, 2019 at 12:35:26PM +0200, Knut Omang wrote:
> On Thu, 2019-08-15 at 10:49 +0200, Greg Kroah-Hartman wrote:
> > > I perfectly agree with you that reducing the hole for a race condition 
> > > is generally a bad idea, but from the above mail thread 
> > > it seems that's the only available choice for older kernels?
> > 
> > I have no idea, but please, do not use that pattern of code as it is
> > racy in all kernels, from all of time.
> 
> Ok, will remove it :-)
> 
> I tried in vain to find the commit from Al Viro that made the code safe,
> to identify which kernels that are safe from this issue,
> but he has a **lot** of commits, do you have a clue for what/where to look?
> 
> It will be good to have a mention/comment on this for future reference, 
> like the earliest kernel version where this is safe.

Always use a "newer" kernel to be "safe" and you will be fine :)

> Maybe we can even get rid of some more of the remaining of these too..
> (I notice there's 65 cases of 'if (!try_module_get(THIS_MODULE))'
> right now)

Something to put on a TODO list somewhere...

thanks,

greg k-h