[PATCH] intel, gma500, lvds: Fix use after free on psb_intel_lvds_init()

[PATCH] intel, gma500, lvds: Fix use after free on psb_intel_lvds_init()

[Jesper Juhl]

In psb_intel_lvds_init(), if we fail to allocate memory for
'psb_intel_connector' we free the memory we previously allocated for
'psb_intel_encoder', but we then proceed to use that free'd pointer
when we do 'psb_intel_encoder->dev_priv = lvds_priv;'.

I believe the proper way to handle this is to simply return after the
allocation for 'psb_intel_connector' has failed. That is what this
patch does.

While I was there anyway, I also removed the pointless 'if
(psb_intel_connector)' before freeing it at the 'failed_connector:'
label - kfree() deals gracefully with NULL pointers, so it is not
needed.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
---
 drivers/gpu/drm/gma500/psb_intel_lvds.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

 I considered adding a new label at the end and use a goto instead, but
 settled on this minimal solution. If consolidating all exits from the 
 function is prefered then I can rework the patch to do that
 instead. Just let me know.

 Patch is compile tested only since I don't have the hardware to
 actually test it properly.

diff --git a/drivers/gpu/drm/gma500/psb_intel_lvds.c b/drivers/gpu/drm/gma500/psb_intel_lvds.c
index a25e4ca..7d23ef9 100644
--- a/drivers/gpu/drm/gma500/psb_intel_lvds.c
+++ b/drivers/gpu/drm/gma500/psb_intel_lvds.c
@@ -725,6 +725,7 @@ void psb_intel_lvds_init(struct drm_device *dev,
 	if (!psb_intel_connector) {
 		kfree(psb_intel_encoder);
 		dev_err(dev->dev, "psb_intel_connector allocation error\n");
+		return;
 	}
 
 	lvds_priv = kzalloc(sizeof(struct psb_intel_lvds_priv), GFP_KERNEL);
@@ -862,7 +863,6 @@ failed_blc_i2c:
 	drm_encoder_cleanup(encoder);
 	drm_connector_cleanup(connector);
 failed_connector:
-	if (psb_intel_connector)
-		kfree(psb_intel_connector);
+	kfree(psb_intel_connector);
 }
 
-- 
1.7.8.3


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Re: [PATCH] intel, gma500, lvds: Fix use after free on psb_intel_lvds_init()

[Jesper Juhl]

On Sat, 14 Jan 2012, Jesper Juhl wrote:

> In psb_intel_lvds_init(), if we fail to allocate memory for
> 'psb_intel_connector' we free the memory we previously allocated for
> 'psb_intel_encoder', but we then proceed to use that free'd pointer
> when we do 'psb_intel_encoder->dev_priv = lvds_priv;'.
> 
> I believe the proper way to handle this is to simply return after the
> allocation for 'psb_intel_connector' has failed. That is what this
> patch does.
> 

Ok, so I just noticed that we may also leak 'psb_intel_encoder' if we 
'goto failed_connector;'. Might as well fix that as well in the same 
patch.

So please just ignore this one. I'll submit a new one in a little 
while that handles both leaks.

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[PATCH] intel, gma500, lvds: Fix use after free and mem leak in psb_intel_lvds_init()

[Jesper Juhl]

In psb_intel_lvds_init(), if we fail to allocate memory for
'psb_intel_connector' we free the memory we previously allocated for
'psb_intel_encoder', but we then proceed to use that free'd pointer
when we do 'psb_intel_encoder->dev_priv = lvds_priv;'.

We may also leak the memory we allocated for 'psb_intel_encoder' if we 
'goto failed_connector;' and the variable goes out of scope.

While I was there anyway, I also removed the pointless 'if
(psb_intel_connector)' before freeing it at the 'failed_connector:'
label - kfree() deals gracefully with NULL pointers, so it is not
needed.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
---
 drivers/gpu/drm/gma500/psb_intel_lvds.c |    9 ++++-----
 1 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/gma500/psb_intel_lvds.c b/drivers/gpu/drm/gma500/psb_intel_lvds.c
index a25e4ca..0a43758 100644
--- a/drivers/gpu/drm/gma500/psb_intel_lvds.c
+++ b/drivers/gpu/drm/gma500/psb_intel_lvds.c
@@ -713,7 +713,6 @@ void psb_intel_lvds_init(struct drm_device *dev,
 
 	psb_intel_encoder =
 			kzalloc(sizeof(struct psb_intel_encoder), GFP_KERNEL);
-
 	if (!psb_intel_encoder) {
 		dev_err(dev->dev, "psb_intel_encoder allocation error\n");
 		return;
@@ -721,10 +720,9 @@ void psb_intel_lvds_init(struct drm_device *dev,
 
 	psb_intel_connector =
 		kzalloc(sizeof(struct psb_intel_connector), GFP_KERNEL);
-
 	if (!psb_intel_connector) {
-		kfree(psb_intel_encoder);
 		dev_err(dev->dev, "psb_intel_connector allocation error\n");
+		goto failed_encoder;
 	}
 
 	lvds_priv = kzalloc(sizeof(struct psb_intel_lvds_priv), GFP_KERNEL);
@@ -862,7 +860,8 @@ failed_blc_i2c:
 	drm_encoder_cleanup(encoder);
 	drm_connector_cleanup(connector);
 failed_connector:
-	if (psb_intel_connector)
-		kfree(psb_intel_connector);
+	kfree(psb_intel_connector);
+failed_encoder:
+	kfree(psb_intel_encoder);
 }
 
-- 
1.7.8.3


-- 
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Re: [PATCH] intel, gma500, lvds: Fix use after free and mem leak in psb_intel_lvds_init()

[Patrik Jakobsson]

On Sat, Jan 14, 2012 at 10:15 PM, Jesper Juhl wrote:
> In psb_intel_lvds_init(), if we fail to allocate memory for
> 'psb_intel_connector' we free the memory we previously allocated for
> 'psb_intel_encoder', but we then proceed to use that free'd pointer
> when we do 'psb_intel_encoder->dev_priv = lvds_priv;'.
>
> We may also leak the memory we allocated for 'psb_intel_encoder' if we
> 'goto failed_connector;' and the variable goes out of scope.
>
> While I was there anyway, I also removed the pointless 'if
> (psb_intel_connector)' before freeing it at the 'failed_connector:'
> label - kfree() deals gracefully with NULL pointers, so it is not
> needed.

My bad, thanks for fixing

Re: [PATCH] intel, gma500, lvds: Fix use after free and mem leak in psb_intel_lvds_init()

[Jesper Juhl]

On Tue, 17 Jan 2012, Patrik Jakobsson wrote:

> On Sat, Jan 14, 2012 at 10:15 PM, Jesper Juhl wrote:
> > In psb_intel_lvds_init(), if we fail to allocate memory for
> > 'psb_intel_connector' we free the memory we previously allocated for
> > 'psb_intel_encoder', but we then proceed to use that free'd pointer
> > when we do 'psb_intel_encoder->dev_priv = lvds_priv;'.
> >
> > We may also leak the memory we allocated for 'psb_intel_encoder' if we
> > 'goto failed_connector;' and the variable goes out of scope.
> >
> > While I was there anyway, I also removed the pointless 'if
> > (psb_intel_connector)' before freeing it at the 'failed_connector:'
> > label - kfree() deals gracefully with NULL pointers, so it is not
> > needed.
> 
> My bad, thanks for fixing

No problem :-) Now I just hope that it will get merged :-)

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