[PATCH] drm/gma500: Fix out-of-bounds access to struct drm_device.vblank[]

[Daniel Vetter]

On Thu, Nov 05, 2020 at 08:02:56PM +0100, Thomas Zimmermann wrote:
> The gma500 driver expects 3 pipelines in several it's IRQ functions.
> Accessing struct drm_device.vblank[], this fails with devices that only
> have 2 pipelines. An example KASAN report is shown below.
> 
>   [   62.267688] ==================================================================
>   [   62.268856] BUG: KASAN: slab-out-of-bounds in psb_irq_postinstall+0x250/0x3c0 [gma500_gfx]
>   [   62.269450] Read of size 1 at addr ffff8880012bc6d0 by task systemd-udevd/285
>   [   62.269949]
>   [   62.270192] CPU: 0 PID: 285 Comm: systemd-udevd Tainted: G            E     5.10.0-rc1-1-default+ #572
>   [   62.270807] Hardware name:  /DN2800MT, BIOS MTCDT10N.86A.0164.2012.1213.1024 12/13/2012
>   [   62.271366] Call Trace:
>   [   62.271705]  dump_stack+0xae/0xe5
>   [   62.272180]  print_address_description.constprop.0+0x17/0xf0
>   [   62.272987]  ? psb_irq_postinstall+0x250/0x3c0 [gma500_gfx]
>   [   62.273474]  __kasan_report.cold+0x20/0x38
>   [   62.273989]  ? psb_irq_postinstall+0x250/0x3c0 [gma500_gfx]
>   [   62.274460]  kasan_report+0x3a/0x50
>   [   62.274891]  psb_irq_postinstall+0x250/0x3c0 [gma500_gfx]
>   [   62.275380]  drm_irq_install+0x131/0x1f0
>   <...>
>   [   62.300751] Allocated by task 285:
>   [   62.301223]  kasan_save_stack+0x1b/0x40
>   [   62.301731]  __kasan_kmalloc.constprop.0+0xbf/0xd0
>   [   62.302293]  drmm_kmalloc+0x55/0x100
>   [   62.302773]  drm_vblank_init+0x77/0x210
> 
> Resolve the issue by only handling vblank entries up to the number of
> CRTCs.
> 
> I'm adding a Fixes tag for reference, although the bug has been present
> since the driver's initial commit.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> Fixes: 5c49fd3aa0ab ("gma500: Add the core DRM files and headers")
> Cc: Alan Cox <alan at linux.intel.com>
> Cc: Dave Airlie <airlied at redhat.com>
> Cc: Patrik Jakobsson <patrik.r.jakobsson at gmail.com>
> Cc: dri-devel at lists.freedesktop.org
> Cc: stable at vger.kernel.org#v3.3+

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/gma500/psb_irq.c | 34 +++++++++++---------------------
>  1 file changed, 12 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/gma500/psb_irq.c b/drivers/gpu/drm/gma500/psb_irq.c
> index 15eb3770d817..361e3a0c5ab6 100644
> --- a/drivers/gpu/drm/gma500/psb_irq.c
> +++ b/drivers/gpu/drm/gma500/psb_irq.c
> @@ -347,6 +347,7 @@ int psb_irq_postinstall(struct drm_device *dev)
>  {
>  	struct drm_psb_private *dev_priv = dev->dev_private;
>  	unsigned long irqflags;
> +	unsigned int i;
>  
>  	spin_lock_irqsave(&dev_priv->irqmask_lock, irqflags);
>  
> @@ -359,20 +360,12 @@ int psb_irq_postinstall(struct drm_device *dev)
>  	PSB_WVDC32(dev_priv->vdc_irq_mask, PSB_INT_ENABLE_R);
>  	PSB_WVDC32(0xFFFFFFFF, PSB_HWSTAM);
>  
> -	if (dev->vblank[0].enabled)
> -		psb_enable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
> -	else
> -		psb_disable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
> -
> -	if (dev->vblank[1].enabled)
> -		psb_enable_pipestat(dev_priv, 1, PIPE_VBLANK_INTERRUPT_ENABLE);
> -	else
> -		psb_disable_pipestat(dev_priv, 1, PIPE_VBLANK_INTERRUPT_ENABLE);
> -
> -	if (dev->vblank[2].enabled)
> -		psb_enable_pipestat(dev_priv, 2, PIPE_VBLANK_INTERRUPT_ENABLE);
> -	else
> -		psb_disable_pipestat(dev_priv, 2, PIPE_VBLANK_INTERRUPT_ENABLE);
> +	for (i = 0; i < dev->num_crtcs; ++i) {
> +		if (dev->vblank[i].enabled)
> +			psb_enable_pipestat(dev_priv, i, PIPE_VBLANK_INTERRUPT_ENABLE);
> +		else
> +			psb_disable_pipestat(dev_priv, i, PIPE_VBLANK_INTERRUPT_ENABLE);
> +	}
>  
>  	if (dev_priv->ops->hotplug_enable)
>  		dev_priv->ops->hotplug_enable(dev, true);
> @@ -385,6 +378,7 @@ void psb_irq_uninstall(struct drm_device *dev)
>  {
>  	struct drm_psb_private *dev_priv = dev->dev_private;
>  	unsigned long irqflags;
> +	unsigned int i;
>  
>  	spin_lock_irqsave(&dev_priv->irqmask_lock, irqflags);
>  
> @@ -393,14 +387,10 @@ void psb_irq_uninstall(struct drm_device *dev)
>  
>  	PSB_WVDC32(0xFFFFFFFF, PSB_HWSTAM);
>  
> -	if (dev->vblank[0].enabled)
> -		psb_disable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
> -
> -	if (dev->vblank[1].enabled)
> -		psb_disable_pipestat(dev_priv, 1, PIPE_VBLANK_INTERRUPT_ENABLE);
> -
> -	if (dev->vblank[2].enabled)
> -		psb_disable_pipestat(dev_priv, 2, PIPE_VBLANK_INTERRUPT_ENABLE);
> +	for (i = 0; i < dev->num_crtcs; ++i) {
> +		if (dev->vblank[i].enabled)
> +			psb_disable_pipestat(dev_priv, i, PIPE_VBLANK_INTERRUPT_ENABLE);
> +	}
>  
>  	dev_priv->vdc_irq_mask &= _PSB_IRQ_SGX_FLAG |
>  				  _PSB_IRQ_MSVDX_FLAG |
> -- 
> 2.29.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch