Nouveau - Sep 2013 - [PATCH] drm/nouveau: avoid null deref on bad arguments to nouveau_vma_getmap

Op 28-08-13 08:29, Pasi K?rkk?inen schreef:
> On Fri, Aug 23, 2013 at 11:20:42PM +0300, Pasi K?rkk?inen wrote:
>> On Thu, Aug 22, 2013 at 09:12:40AM +0200, Maarten Lankhorst wrote:
>>> Op 22-08-13 02:10, Ilia Mirkin schreef:
>>>> The code expects non-VRAM mem nodes to have a pages list. If
that's not
>>>> set, it will do a null deref down the line. Warn on that
condition and
>>>> return an error.
>>>>
>>>> See https://bugs.freedesktop.org/show_bug.cgi?id=64774
>>>>
>>>> Reported-by: Pasi K?rkk?inen <pasik at iki.fi>
>>>> Tested-by: Pasi K?rkk?inen <pasik at iki.fi>
>>>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>>>> Cc: <stable at vger.kernel.org> # 3.8+
>>>> ---
>>>>
>>>> I don't exactly understand what's going on, but this is
just a
>>>> straightforward way to avoid a null deref that you see happens
in the
>>>> bug. I haven't figured out the root cause of this, but
it's getting
>>>> well into the "I have no idea how TTM works" space.
However this seems
>>>> like a bit of defensive programming -- nouveau_vm_map_sg will
pass
>>>> node->pages as a list down, which will be dereferenced by
>>>> nvc0_vm_map_sg. Perhaps the other arguments should make that
>>>> dereferencing not happen, but it definitely was happening here,
as you
>>>> can see in the bug.
>>>>
>>>> Ben/Maarten, I'll let you judge whether this check is
appropriate,
>>>> since like I hope I was able to convey above, I'm just not
really sure :)
>>> Not it really isn't appropriate..
>>>
>>> You'd have to call call nouveau_vm_map_sg_table instead, the
only place that doesn't handle that correctly
>>> is where it's not expected to be called.
>>>
>>> Here, have a completely untested patch to fix things...
>>>
>> Maarten: I've been testing this stuff with Linux 3.10.x, so I had
to modify the patch a bit to make it apply there..
>> I've attached the modified copy that applies to 3.10.9, hopefully I
did the backport correctly.
>>
>> With Linux 3.10.9 and the patch applied the kernel doesn't crash
anymore, and I get this error in dmesg:
>>
>> [   76.105643] nouveau W[     DRM] Trying to create a fb in vram with
valid_domains=00000004
>>
>> Does that help? 
>>
> Any comments? 
>
> Maarten's patch works for me, I get that warning instead of a kernel
crash,
> but it's also a bigger change that doesn't apply to older kernels
as-is.
>
> Ilia's original patch in this thread can be applied to older kernels
as-is,
> and it also prevents the kernel crash from happening.
>
> Should we get both applied, so Ilia's patch can be CC'd to stable ?
>
You haven't understood the root cause then. You're trying to move an
IMPORTED dma-buf into VRAM.
Doing so would seem to work, but at that point it's no longer a dma-buf so
changes done by the exporter
would not show up in nouveau because they no longer refer to the same piece of
memory.

Failing is the only right option here.

~Maarten

On Wed, Aug 28, 2013 at 09:44:15AM +0200, Maarten Lankhorst
wrote:
> Op 28-08-13 08:29, Pasi K?rkk?inen schreef:
> > On Fri, Aug 23, 2013 at 11:20:42PM +0300, Pasi K?rkk?inen wrote:
> >> On Thu, Aug 22, 2013 at 09:12:40AM +0200, Maarten Lankhorst wrote:
> >>> Op 22-08-13 02:10, Ilia Mirkin schreef:
> >>>> The code expects non-VRAM mem nodes to have a pages list.
If that's not
> >>>> set, it will do a null deref down the line. Warn on that
condition and
> >>>> return an error.
> >>>>
> >>>> See https://bugs.freedesktop.org/show_bug.cgi?id=64774
> >>>>
> >>>> Reported-by: Pasi K?rkk?inen <pasik at iki.fi>
> >>>> Tested-by: Pasi K?rkk?inen <pasik at iki.fi>
> >>>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> >>>> Cc: <stable at vger.kernel.org> # 3.8+
> >>>> ---
> >>>>
> >>>> I don't exactly understand what's going on, but
this is just a
> >>>> straightforward way to avoid a null deref that you see
happens in the
> >>>> bug. I haven't figured out the root cause of this, but
it's getting
> >>>> well into the "I have no idea how TTM works"
space. However this seems
> >>>> like a bit of defensive programming -- nouveau_vm_map_sg
will pass
> >>>> node->pages as a list down, which will be dereferenced
by
> >>>> nvc0_vm_map_sg. Perhaps the other arguments should make
that
> >>>> dereferencing not happen, but it definitely was happening
here, as you
> >>>> can see in the bug.
> >>>>
> >>>> Ben/Maarten, I'll let you judge whether this check is
appropriate,
> >>>> since like I hope I was able to convey above, I'm just
not really sure :)
> >>> Not it really isn't appropriate..
> >>>
> >>> You'd have to call call nouveau_vm_map_sg_table instead,
the only place that doesn't handle that correctly
> >>> is where it's not expected to be called.
> >>>
> >>> Here, have a completely untested patch to fix things...
> >>>
> >> Maarten: I've been testing this stuff with Linux 3.10.x, so I
had to modify the patch a bit to make it apply there..
> >> I've attached the modified copy that applies to 3.10.9,
hopefully I did the backport correctly.
> >>
> >> With Linux 3.10.9 and the patch applied the kernel doesn't
crash anymore, and I get this error in dmesg:
> >>
> >> [   76.105643] nouveau W[     DRM] Trying to create a fb in vram
with valid_domains=00000004
> >>
> >> Does that help? 
> >>
> > Any comments? 
> >
> > Maarten's patch works for me, I get that warning instead of a
kernel crash,
> > but it's also a bigger change that doesn't apply to older
kernels as-is.
> >
> > Ilia's original patch in this thread can be applied to older
kernels as-is,
> > and it also prevents the kernel crash from happening.
> >
> > Should we get both applied, so Ilia's patch can be CC'd to
stable ?
> >
> You haven't understood the root cause then. You're trying to move
an IMPORTED dma-buf into VRAM.
> Doing so would seem to work, but at that point it's no longer a dma-buf
so changes done by the exporter
> would not show up in nouveau because they no longer refer to the same piece
of memory.
> 
Yes, that's true, I don't understand the root cause. 
That's mostly because I'm not familiar with the nouveau code/internals. 

> Failing is the only right option here.
>
Sorry but I'm not sure I understand that correctly.. what exactly do you
suggest? What should fail?


Because I'm not familiar with the code (yet) understanding and finding the
root cause
will take time for me.. that's why I was suggesting to meanwhile apply
Ilia's very simple patch
from this thread which actually prevents the hard kernel crash from happening,
because it seems
like an unharmful fix to have to protect against this kind of bugs (the root
cause) ?
Or is that unacceptable? 

(To recap: The kernel crash happens very often when trying to use the nouveau
adapter in Optimus mode, with all kernels at least 3.8+, and it's very
annoying that your laptop crashes when trying to enable a nouveau output. So
Ilia's patch doesn't make the driver working properly, but at least it
prevents the hard kernel crash from happening. The crash bug is in many kernel
versions, including the long-term v3.10 tree. I've had the crash happening
with 3.8.x, 3.9.x and 3.10.x)

All comments welcome.

Thanks,

-- Pasi

Op 03-09-13 16:20, Pasi K?rkk?inen schreef:
> On Wed, Aug 28, 2013 at 09:44:15AM +0200, Maarten Lankhorst wrote:
>> Op 28-08-13 08:29, Pasi K?rkk?inen schreef:
>>> On Fri, Aug 23, 2013 at 11:20:42PM +0300, Pasi K?rkk?inen wrote:
>>>> On Thu, Aug 22, 2013 at 09:12:40AM +0200, Maarten Lankhorst
wrote:
>>>>> Op 22-08-13 02:10, Ilia Mirkin schreef:
>>>>>> The code expects non-VRAM mem nodes to have a pages
list. If that's not
>>>>>> set, it will do a null deref down the line. Warn on
that condition and
>>>>>> return an error.
>>>>>>
>>>>>> See https://bugs.freedesktop.org/show_bug.cgi?id=64774
>>>>>>
>>>>>> Reported-by: Pasi K?rkk?inen <pasik at iki.fi>
>>>>>> Tested-by: Pasi K?rkk?inen <pasik at iki.fi>
>>>>>> Signed-off-by: Ilia Mirkin <imirkin at
alum.mit.edu>
>>>>>> Cc: <stable at vger.kernel.org> # 3.8+
>>>>>> ---
>>>>>>
>>>>>> I don't exactly understand what's going on, but
this is just a
>>>>>> straightforward way to avoid a null deref that you see
happens in the
>>>>>> bug. I haven't figured out the root cause of this,
but it's getting
>>>>>> well into the "I have no idea how TTM works"
space. However this seems
>>>>>> like a bit of defensive programming --
nouveau_vm_map_sg will pass
>>>>>> node->pages as a list down, which will be
dereferenced by
>>>>>> nvc0_vm_map_sg. Perhaps the other arguments should make
that
>>>>>> dereferencing not happen, but it definitely was
happening here, as you
>>>>>> can see in the bug.
>>>>>>
>>>>>> Ben/Maarten, I'll let you judge whether this check
is appropriate,
>>>>>> since like I hope I was able to convey above, I'm
just not really sure :)
>>>>> Not it really isn't appropriate..
>>>>>
>>>>> You'd have to call call nouveau_vm_map_sg_table
instead, the only place that doesn't handle that correctly
>>>>> is where it's not expected to be called.
>>>>>
>>>>> Here, have a completely untested patch to fix things...
>>>>>
>>>> Maarten: I've been testing this stuff with Linux 3.10.x, so
I had to modify the patch a bit to make it apply there..
>>>> I've attached the modified copy that applies to 3.10.9,
hopefully I did the backport correctly.
>>>>
>>>> With Linux 3.10.9 and the patch applied the kernel doesn't
crash anymore, and I get this error in dmesg:
>>>>
>>>> [   76.105643] nouveau W[     DRM] Trying to create a fb in
vram with valid_domains=00000004
>>>>
>>>> Does that help? 
>>>>
>>> Any comments? 
>>>
>>> Maarten's patch works for me, I get that warning instead of a
kernel crash,
>>> but it's also a bigger change that doesn't apply to older
kernels as-is.
>>>
>>> Ilia's original patch in this thread can be applied to older
kernels as-is,
>>> and it also prevents the kernel crash from happening.
>>>
>>> Should we get both applied, so Ilia's patch can be CC'd to
stable ?
>>>
>> You haven't understood the root cause then. You're trying to
move an IMPORTED dma-buf into VRAM.
>> Doing so would seem to work, but at that point it's no longer a
dma-buf so changes done by the exporter
>> would not show up in nouveau because they no longer refer to the same
piece of memory.
>>
> Yes, that's true, I don't understand the root cause. 
> That's mostly because I'm not familiar with the nouveau
code/internals.
>
>
>> Failing is the only right option here.
>>
> Sorry but I'm not sure I understand that correctly.. what exactly do
you suggest? What should fail?
>
>
> Because I'm not familiar with the code (yet) understanding and finding
the root cause
> will take time for me.. that's why I was suggesting to meanwhile apply
Ilia's very simple patch
> from this thread which actually prevents the hard kernel crash from
happening, because it seems
> like an unharmful fix to have to protect against this kind of bugs (the
root cause) ?
> Or is that unacceptable? 
>
> (To recap: The kernel crash happens very often when trying to use the
nouveau adapter in Optimus mode, with all kernels at least 3.8+, and it's
very annoying that your laptop crashes when trying to enable a nouveau output.
So Ilia's patch doesn't make the driver working properly, but at least
it prevents the hard kernel crash from happening. The crash bug is in many
kernel versions, including the long-term v3.10 tree. I've had the crash
happening with 3.8.x, 3.9.x and 3.10.x)
The fix probably requires commit fdfb8332651db7a280851dfccfc4f0cff4bcd052 to
apply cleanly "drm/nouveau: fix some error-path leaks in fbcon handling
code"
> All comments welcome.
>
> Thanks,
>
> -- Pasi
>