[Intel-gfx] [PATCH 1/5] drm: Kernel Crash in drm_unlock

[Antoine, Peter]

I picked up this work due to the following Jira ticket created by the
security team (on Android) and was asked to give it a second look and
found a few more issues with the hw lock code.

https://jira01.devtools.intel.com/browse/GMINL-5388
I/O control on /dev/dri/card0 crashes the kernel (0x4008642b)

It also stops Linux as it kills the driver, I guess it might be possible
to reload the gfx driver. On a unpatched system the test that is
included in the issue or the igt test that has been posted for the issue
will show the problem.

I ran the test on an unpatched system here and the gui stopped and the
keyboard stopped responding, so I rebooted. With the patched system I
did not need to reboot.

Should I change the SIGTERM to SIGSEGV, not quite the same thing but
tooling is better at handling a segfault than a SIGTERM and the
application that calls this IOCTL is using an uninitialised hw lock so
it is kind of the same as differencing an uninitialised pointer (kind
of). Or, I could just remove it, but the bug has been in the code for at
least two years (and known about), and I would guess that any code that
is calling this is fuzzing the IOCTLs (as this is how the security team
found it) and we should reward them with a application exit.

Peter. 


On Thu, 2015-04-23 at 15:39 +0100, Chris Wilson wrote:
> On Thu, Apr 23, 2015 at 02:34:24PM +0000, Antoine, Peter wrote:
> > Before the patch the system required rebooting (driver crash and/or kernel panic).
> > Now the application gets terminated.
> 
> It should have an GPF which should not have required a reboot, but
> terminated the application. Unless you set it to automatically reboot.
> -Chris
>