[PATCH v2] privates: Clear screen-specific keys during CloseScreen

[Aaron Plattner]

On 09/17/2015 03:57 PM, Keith Packard wrote:
> Aaron Plattner <aplattner at nvidia.com> writes:
> 
>> The modesetting driver corrupts memory when used after a server regeneration
>> because not enough memory is allocated for its pixmap privates.  This happens
>> because its call to dixRegisterScreenSpecificPrivateKey() does nothing because
>> key->initialized is still TRUE from the first server generation.  However, the
>> key is not in the screen's linked list of screen-specific privates because
>> that's freed and reallocated during the server generation loop in dix_main().
>>
>> Fix this by clearing key->initialized after CloseScreen.  Move the call to
>> dixFreeScreenSpecificPrivates() after the call to CloseScreen, in case a
>> driver's CloseScreen needs a screen private for something.
> 
> Oh, if you're just going to reset the key->initialized value, you should
> leave the call above CloseScreen. That's because the storage for the key
> may well be allocated by the driver, and would be freed by CloseScreen.

Oh, duh, gotcha.  Sorry for being dense.

>> I was thinking about your suggestion of ignoring key->initialized backwards
>> yesterday.  I think that would work too, but I think this is clearer and more
>> explicit.
> 
> Cool, this does seem like the most conservative plan possible. Let's
> just keep doing that before CloseScreen is called to avoid storing
> through freed memory.

Hopefully third time's the charm.

-- 
Aaron