question regarding nvc0_instmem_suspend()

question regarding nvc0_instmem_suspend()

[Dan Carpenter]

Smatch thinks there is a buffer overflow in nvc0_instmem_suspend() and
I've looked at it, but I don't understand the code.

drivers/gpu/drm/nouveau/nvc0_instmem.c +152 nvc0_instmem_suspend(10)
	error: buffer overflow 'dev_priv->susres.ramin_copy' 16384 <= 1835008

   141  int
   142  nvc0_instmem_suspend(struct drm_device *dev)
   143  {
   144          struct drm_nouveau_private *dev_priv = dev->dev_private;
   145          int i;
   146
   147          dev_priv->susres.ramin_copy = vmalloc(65536);

	dev_priv->susres.ramin_copy is an array of 16384 u32 elements
	(65536 bytes).

   148          if (!dev_priv->susres.ramin_copy)
   149                  return -ENOMEM;
   150
   151          for (i = 0x700000; i < 0x710000; i += 4)
   152                  dev_priv->susres.ramin_copy[i/4] = nv_rd32(dev, i);

	0x700000 / 4 is 1835008 so we're way past the end of the array
	and then we get larger.

   153          return 0;
   154  }

Normally when I'm this confused it's because I'm missing something 
obvious.  :P  Can you help me out?

regards,
dan carpenter

Re: question regarding nvc0_instmem_suspend()

[Luca Tettamanti]

On Fri, Aug 13, 2010 at 11:39 PM, Dan Carpenter <error27@gmail.com> wrote:
> Smatch thinks there is a buffer overflow in nvc0_instmem_suspend() and
> I've looked at it, but I don't understand the code.
>
> drivers/gpu/drm/nouveau/nvc0_instmem.c +152 nvc0_instmem_suspend(10)
>        error: buffer overflow 'dev_priv->susres.ramin_copy' 16384 <= 1835008
>
>   141  int
>   142  nvc0_instmem_suspend(struct drm_device *dev)
>   143  {
>   144          struct drm_nouveau_private *dev_priv = dev->dev_private;
>   145          int i;
>   146
>   147          dev_priv->susres.ramin_copy = vmalloc(65536);
>
>        dev_priv->susres.ramin_copy is an array of 16384 u32 elements
>        (65536 bytes).
>
>   148          if (!dev_priv->susres.ramin_copy)
>   149                  return -ENOMEM;
>   150
>   151          for (i = 0x700000; i < 0x710000; i += 4)
>   152                  dev_priv->susres.ramin_copy[i/4] = nv_rd32(dev, i);
>
>        0x700000 / 4 is 1835008 so we're way past the end of the array
>        and then we get larger.

I guess that it should be something like:

    base = 0x700000;
    for (i = 0; i < 0x10000; i += 4)
        dev_priv->susres.ramin_copy[i/4] = nv_rd32(dev, base + i);


Luca
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Re: question regarding nvc0_instmem_suspend()

[Ben Skeggs]

On Fri, 2010-08-13 at 23:59 +0200, Luca Tettamanti wrote:
> On Fri, Aug 13, 2010 at 11:39 PM, Dan Carpenter <error27@gmail.com> wrote:
> > Smatch thinks there is a buffer overflow in nvc0_instmem_suspend() and
> > I've looked at it, but I don't understand the code.
> >
> > drivers/gpu/drm/nouveau/nvc0_instmem.c +152 nvc0_instmem_suspend(10)
> >        error: buffer overflow 'dev_priv->susres.ramin_copy' 16384 <= 1835008
> >
> >   141  int
> >   142  nvc0_instmem_suspend(struct drm_device *dev)
> >   143  {
> >   144          struct drm_nouveau_private *dev_priv = dev->dev_private;
> >   145          int i;
> >   146
> >   147          dev_priv->susres.ramin_copy = vmalloc(65536);
> >
> >        dev_priv->susres.ramin_copy is an array of 16384 u32 elements
> >        (65536 bytes).
> >
> >   148          if (!dev_priv->susres.ramin_copy)
> >   149                  return -ENOMEM;
> >   150
> >   151          for (i = 0x700000; i < 0x710000; i += 4)
> >   152                  dev_priv->susres.ramin_copy[i/4] = nv_rd32(dev, i);
> >
> >        0x700000 / 4 is 1835008 so we're way past the end of the array
> >        and then we get larger.
> 
> I guess that it should be something like:
> 
>     base = 0x700000;
>     for (i = 0; i < 0x10000; i += 4)
>         dev_priv->susres.ramin_copy[i/4] = nv_rd32(dev, base + i);
Oops, what a thinko.  I've pushed a fix to nouveau git, I'll send it on
for inclusion in 2.6.36.

Ben.
> 
> 
> Luca