linux-kernel - Re: [BUG] BUG: kernel NULL pointer dereference at ttm_device

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Date: Tue, 23 Jan 2024 09:35:19 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Christian König <christian.koenig@....com>
Cc: Dave Airlie <airlied@...il.com>, "Bhardwaj, Rajneesh"
 <rajneesh.bhardwaj@....com>, Linus Torvalds
 <torvalds@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Felix
 Kuehling <Felix.Kuehling@....com>, dri-devel@...ts.freedesktop.org, Fedor
 Pchelkin <pchelkin@...ras.ru>
Subject: Re: [BUG] BUG: kernel NULL pointer dereference at
 ttm_device_init+0xb4

On Tue, 23 Jan 2024 10:43:04 +0100
Christian König <christian.koenig@....com> wrote:

> While applying the fix a week ago I was under the impression that QXL 
> doesn't use a device structure because it doesn't have one and so can't 
> give anything meaningful for this parameter.
> 
> If QXL does have a device structure and can provide it I would rather 
> like to go down this route and make the device and with it the numa node 
> mandatory for drivers to specify.

Then at a minimum my original fix should be applied. Perhaps with a warning
too. That is, I added at the beginning of that function:

	if (!dev)
		return -EINVAL;

Could have that be:

	if (WARN_ON_ONCE(!dev))
		return -EINVAL;

In any case, it should not cause the system to crash.

-- Steve