[patch] gpio: potential null dereference

[patch] gpio: potential null dereference

[Dan Carpenter]

Smatch found a potential null dereference in gpio_setup_irq().  The 
"pdesc" variable is allocated with idr_find() that can return NULL.  If
gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
would OOPs here.

Signed-off-by: Dan Carpenter <error27@gmail.com>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 76be229..eb0c3fe 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -416,7 +416,8 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 	return 0;
 
 free_sd:
-	sysfs_put(pdesc->value_sd);
+	if (pdesc)
+		sysfs_put(pdesc->value_sd);
 free_id:
 	idr_remove(&pdesc_idr, id);
 	desc->flags &= GPIO_FLAGS_MASK;

[patch] gpio: potential null dereference

[Dan Carpenter]

Smatch found a potential null dereference in gpio_setup_irq().  The 
"pdesc" variable is allocated with idr_find() that can return NULL.  If
gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
would OOPs here.

Signed-off-by: Dan Carpenter <error27@gmail.com>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 76be229..eb0c3fe 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -416,7 +416,8 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 	return 0;
 
 free_sd:
-	sysfs_put(pdesc->value_sd);
+	if (pdesc)
+		sysfs_put(pdesc->value_sd);
 free_id:
 	idr_remove(&pdesc_idr, id);
 	desc->flags &= GPIO_FLAGS_MASK;

Re: [patch] gpio: potential null dereference

[Daniel Glöckner]

On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
> Smatch found a potential null dereference in gpio_setup_irq().  The 
> "pdesc" variable is allocated with idr_find() that can return NULL.  If
> gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
> would OOPs here.

idr_find() doesn't allocate, idr_get_new_above() does.
Assuming idr_find() never fails for an id if idr_get_new_above()
successfully allocated that id, I don't think we can reach that
line with pdesc being NULL:

- There are two gotos leading to free_sd
- #2 is after a block that allocates pdesc
- #1 is in an if (!gpio_flags) block
- We exit early if ((desc->flags & GPIO_TRIGGER_MASK) = gpio_flags)
- Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
- Trigger flags are added to desc->flags only after we have
  successfully allocated pdesc (i.e. right before return 0)
- We start off with no trigger flags set

  Daniel


-- 
Dipl.-Math. Daniel Glöckner, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax -11, Bahnhofsallee 1b, 37081 Göttingen, Germany
Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
Geschäftsführung: Dr. Uwe Kracke, Ust-IdNr.: DE 205 198 055

emlix - your embedded linux partner
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Re: [patch] gpio: potential null dereference

[Daniel Glöckner]

On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
> Smatch found a potential null dereference in gpio_setup_irq().  The 
> "pdesc" variable is allocated with idr_find() that can return NULL.  If
> gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
> would OOPs here.

idr_find() doesn't allocate, idr_get_new_above() does.
Assuming idr_find() never fails for an id if idr_get_new_above()
successfully allocated that id, I don't think we can reach that
line with pdesc being NULL:

- There are two gotos leading to free_sd
- #2 is after a block that allocates pdesc
- #1 is in an if (!gpio_flags) block
- We exit early if ((desc->flags & GPIO_TRIGGER_MASK) == gpio_flags)
- Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
- Trigger flags are added to desc->flags only after we have
  successfully allocated pdesc (i.e. right before return 0)
- We start off with no trigger flags set

  Daniel


-- 
Dipl.-Math. Daniel Glöckner, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax -11, Bahnhofsallee 1b, 37081 Göttingen, Germany
Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
Geschäftsführung: Dr. Uwe Kracke, Ust-IdNr.: DE 205 198 055

emlix - your embedded linux partner

Re: [patch] gpio: potential null dereference

[Andrew Morton]

On Tue, 27 Apr 2010 01:05:15 +0200
Daniel Gl__ckner <dg@emlix.com> wrote:

> On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
> > Smatch found a potential null dereference in gpio_setup_irq().  The 
> > "pdesc" variable is allocated with idr_find() that can return NULL.  If
> > gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
> > would OOPs here.
> 
> idr_find() doesn't allocate, idr_get_new_above() does.
> Assuming idr_find() never fails for an id if idr_get_new_above()
> successfully allocated that id, I don't think we can reach that
> line with pdesc being NULL:
> 
> - There are two gotos leading to free_sd
> - #2 is after a block that allocates pdesc
> - #1 is in an if (!gpio_flags) block
> - We exit early if ((desc->flags & GPIO_TRIGGER_MASK) = gpio_flags)
> - Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
> - Trigger flags are added to desc->flags only after we have
>   successfully allocated pdesc (i.e. right before return 0)
> - We start off with no trigger flags set
> 

heh, thanks.  I figured that something like that might be going on but
couldn't be bothered picking through it all.

That being said, the above sequence of steps is awfully (and unusually)
intricate and is hence hard to preserve and could get broken at some
future time.

Re: [patch] gpio: potential null dereference

[Andrew Morton]

On Tue, 27 Apr 2010 01:05:15 +0200
Daniel Gl__ckner <dg@emlix.com> wrote:

> On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
> > Smatch found a potential null dereference in gpio_setup_irq().  The 
> > "pdesc" variable is allocated with idr_find() that can return NULL.  If
> > gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
> > would OOPs here.
> 
> idr_find() doesn't allocate, idr_get_new_above() does.
> Assuming idr_find() never fails for an id if idr_get_new_above()
> successfully allocated that id, I don't think we can reach that
> line with pdesc being NULL:
> 
> - There are two gotos leading to free_sd
> - #2 is after a block that allocates pdesc
> - #1 is in an if (!gpio_flags) block
> - We exit early if ((desc->flags & GPIO_TRIGGER_MASK) == gpio_flags)
> - Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
> - Trigger flags are added to desc->flags only after we have
>   successfully allocated pdesc (i.e. right before return 0)
> - We start off with no trigger flags set
> 

heh, thanks.  I figured that something like that might be going on but
couldn't be bothered picking through it all.

That being said, the above sequence of steps is awfully (and unusually)
intricate and is hence hard to preserve and could get broken at some
future time.

Re: [patch] gpio: potential null dereference

[Dan Carpenter]

On Tue, Apr 27, 2010 at 01:05:15AM +0200, Daniel Glöckner wrote:
> On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
> > Smatch found a potential null dereference in gpio_setup_irq().  The 
> > "pdesc" variable is allocated with idr_find() that can return NULL.  If
> > gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
> > would OOPs here.
> 
> idr_find() doesn't allocate, idr_get_new_above() does.
> Assuming idr_find() never fails for an id if idr_get_new_above()
> successfully allocated that id, I don't think we can reach that
> line with pdesc being NULL:
> 
> - There are two gotos leading to free_sd
> - #2 is after a block that allocates pdesc
> - #1 is in an if (!gpio_flags) block
> - We exit early if ((desc->flags & GPIO_TRIGGER_MASK) = gpio_flags)
> - Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
> - Trigger flags are added to desc->flags only after we have
>   successfully allocated pdesc (i.e. right before return 0)
> - We start off with no trigger flags set
> 

Are you sure?  If we know that the call to idr_find() returns a valid 
pointer we could remove a lot of error handling code...

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 76be229..54922a6 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -330,14 +330,6 @@ static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
 	return IRQ_HANDLED;
 }
 
-static void gpio_notify_sysfs(struct work_struct *work)
-{
-	struct poll_desc	*pdesc;
-
-	pdesc = container_of(work, struct poll_desc, work);
-	sysfs_notify_dirent(pdesc->value_sd);
-}
-
 static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 		unsigned long gpio_flags)
 {
@@ -353,14 +345,10 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 		return -EIO;
 
 	id = desc->flags >> PDESC_ID_SHIFT;
+	/* idr_find() always returns a valid pointer here */
 	pdesc = idr_find(&pdesc_idr, id);
-	if (pdesc) {
-		free_irq(irq, &pdesc->work);
-		cancel_work_sync(&pdesc->work);
-	}
 
 	desc->flags &= ~GPIO_TRIGGER_MASK;
-
 	if (!gpio_flags) {
 		ret = 0;
 		goto free_sd;
@@ -374,39 +362,6 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
 			IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
 
-	if (!pdesc) {
-		pdesc = kmalloc(sizeof(*pdesc), GFP_KERNEL);
-		if (!pdesc) {
-			ret = -ENOMEM;
-			goto err_out;
-		}
-
-		do {
-			ret = -ENOMEM;
-			if (idr_pre_get(&pdesc_idr, GFP_KERNEL))
-				ret = idr_get_new_above(&pdesc_idr,
-						pdesc, 1, &id);
-		} while (ret = -EAGAIN);
-
-		if (ret)
-			goto free_mem;
-
-		desc->flags &= GPIO_FLAGS_MASK;
-		desc->flags |= (unsigned long)id << PDESC_ID_SHIFT;
-
-		if (desc->flags >> PDESC_ID_SHIFT != id) {
-			ret = -ERANGE;
-			goto free_id;
-		}
-
-		pdesc->value_sd = sysfs_get_dirent(dev->kobj.sd, "value");
-		if (!pdesc->value_sd) {
-			ret = -ENODEV;
-			goto free_id;
-		}
-		INIT_WORK(&pdesc->work, gpio_notify_sysfs);
-	}
-
 	ret = request_irq(irq, gpio_sysfs_irq, irq_flags,
 			"gpiolib", &pdesc->work);
 	if (ret)
@@ -417,12 +372,9 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 
 free_sd:
 	sysfs_put(pdesc->value_sd);
-free_id:
 	idr_remove(&pdesc_idr, id);
 	desc->flags &= GPIO_FLAGS_MASK;
-free_mem:
 	kfree(pdesc);
-err_out:
 	return ret;
 }
 

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Re: [patch] gpio: potential null dereference

[Dan Carpenter]

On Tue, Apr 27, 2010 at 01:05:15AM +0200, Daniel Glöckner wrote:
> On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
> > Smatch found a potential null dereference in gpio_setup_irq().  The 
> > "pdesc" variable is allocated with idr_find() that can return NULL.  If
> > gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
> > would OOPs here.
> 
> idr_find() doesn't allocate, idr_get_new_above() does.
> Assuming idr_find() never fails for an id if idr_get_new_above()
> successfully allocated that id, I don't think we can reach that
> line with pdesc being NULL:
> 
> - There are two gotos leading to free_sd
> - #2 is after a block that allocates pdesc
> - #1 is in an if (!gpio_flags) block
> - We exit early if ((desc->flags & GPIO_TRIGGER_MASK) == gpio_flags)
> - Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
> - Trigger flags are added to desc->flags only after we have
>   successfully allocated pdesc (i.e. right before return 0)
> - We start off with no trigger flags set
> 

Are you sure?  If we know that the call to idr_find() returns a valid 
pointer we could remove a lot of error handling code...

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 76be229..54922a6 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -330,14 +330,6 @@ static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
 	return IRQ_HANDLED;
 }
 
-static void gpio_notify_sysfs(struct work_struct *work)
-{
-	struct poll_desc	*pdesc;
-
-	pdesc = container_of(work, struct poll_desc, work);
-	sysfs_notify_dirent(pdesc->value_sd);
-}
-
 static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 		unsigned long gpio_flags)
 {
@@ -353,14 +345,10 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 		return -EIO;
 
 	id = desc->flags >> PDESC_ID_SHIFT;
+	/* idr_find() always returns a valid pointer here */
 	pdesc = idr_find(&pdesc_idr, id);
-	if (pdesc) {
-		free_irq(irq, &pdesc->work);
-		cancel_work_sync(&pdesc->work);
-	}
 
 	desc->flags &= ~GPIO_TRIGGER_MASK;
-
 	if (!gpio_flags) {
 		ret = 0;
 		goto free_sd;
@@ -374,39 +362,6 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
 			IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
 
-	if (!pdesc) {
-		pdesc = kmalloc(sizeof(*pdesc), GFP_KERNEL);
-		if (!pdesc) {
-			ret = -ENOMEM;
-			goto err_out;
-		}
-
-		do {
-			ret = -ENOMEM;
-			if (idr_pre_get(&pdesc_idr, GFP_KERNEL))
-				ret = idr_get_new_above(&pdesc_idr,
-						pdesc, 1, &id);
-		} while (ret == -EAGAIN);
-
-		if (ret)
-			goto free_mem;
-
-		desc->flags &= GPIO_FLAGS_MASK;
-		desc->flags |= (unsigned long)id << PDESC_ID_SHIFT;
-
-		if (desc->flags >> PDESC_ID_SHIFT != id) {
-			ret = -ERANGE;
-			goto free_id;
-		}
-
-		pdesc->value_sd = sysfs_get_dirent(dev->kobj.sd, "value");
-		if (!pdesc->value_sd) {
-			ret = -ENODEV;
-			goto free_id;
-		}
-		INIT_WORK(&pdesc->work, gpio_notify_sysfs);
-	}
-
 	ret = request_irq(irq, gpio_sysfs_irq, irq_flags,
 			"gpiolib", &pdesc->work);
 	if (ret)
@@ -417,12 +372,9 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
 
 free_sd:
 	sysfs_put(pdesc->value_sd);
-free_id:
 	idr_remove(&pdesc_idr, id);
 	desc->flags &= GPIO_FLAGS_MASK;
-free_mem:
 	kfree(pdesc);
-err_out:
 	return ret;
 }
 

Re: [patch] gpio: potential null dereference

[Daniel Glöckner]

On 04/27/2010 11:05 AM, Dan Carpenter wrote:
> On Tue, Apr 27, 2010 at 01:05:15AM +0200, Daniel Glöckner wrote:
>> On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
>>> Smatch found a potential null dereference in gpio_setup_irq().  The 
>>> "pdesc" variable is allocated with idr_find() that can return NULL.  If
>>> gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
>>> would OOPs here.
>> idr_find() doesn't allocate, idr_get_new_above() does.
>> Assuming idr_find() never fails for an id if idr_get_new_above()
>> successfully allocated that id, I don't think we can reach that
>> line with pdesc being NULL:
>>
>> - There are two gotos leading to free_sd
>> - #2 is after a block that allocates pdesc
>> - #1 is in an if (!gpio_flags) block
>> - We exit early if ((desc->flags & GPIO_TRIGGER_MASK) = gpio_flags)
>> - Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
>> - Trigger flags are added to desc->flags only after we have
>>   successfully allocated pdesc (i.e. right before return 0)
>> - We start off with no trigger flags set
>>
> 
> Are you sure?  If we know that the call to idr_find() returns a valid 
> pointer we could remove a lot of error handling code...

It returns a valid pointer iff (desc->flags & GPIO_TRIGGER_MASK).

When !(desc->flags & GPIO_TRIGGER_MASK) it returns NULL and everything
gets allocated (unless !gpio_flags as well). What you wanted to remove
is the allocation code, not error handling code. It is always run when
the trigger is set from "none" to something else.

  Daniel

-- 
Dipl.-Math. Daniel Glöckner, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax -11, Bahnhofsallee 1b, 37081 Göttingen, Germany
Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
Geschäftsführer: Dr. Uwe Kracke, Ust-IdNr.: DE 205 198 055

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Re: [patch] gpio: potential null dereference

[Daniel Glöckner]

On 04/27/2010 11:05 AM, Dan Carpenter wrote:
> On Tue, Apr 27, 2010 at 01:05:15AM +0200, Daniel Glöckner wrote:
>> On Mon, Apr 26, 2010 at 09:25:20PM +0200, Dan Carpenter wrote:
>>> Smatch found a potential null dereference in gpio_setup_irq().  The 
>>> "pdesc" variable is allocated with idr_find() that can return NULL.  If
>>> gpio_setup_irq() is called with 0 as gpio_flags and "pdesc" is null, it
>>> would OOPs here.
>> idr_find() doesn't allocate, idr_get_new_above() does.
>> Assuming idr_find() never fails for an id if idr_get_new_above()
>> successfully allocated that id, I don't think we can reach that
>> line with pdesc being NULL:
>>
>> - There are two gotos leading to free_sd
>> - #2 is after a block that allocates pdesc
>> - #1 is in an if (!gpio_flags) block
>> - We exit early if ((desc->flags & GPIO_TRIGGER_MASK) == gpio_flags)
>> - Therefore (desc->flags & GPIO_TRIGGER_MASK) must be != 0 to reach #1
>> - Trigger flags are added to desc->flags only after we have
>>   successfully allocated pdesc (i.e. right before return 0)
>> - We start off with no trigger flags set
>>
> 
> Are you sure?  If we know that the call to idr_find() returns a valid 
> pointer we could remove a lot of error handling code...

It returns a valid pointer iff (desc->flags & GPIO_TRIGGER_MASK).

When !(desc->flags & GPIO_TRIGGER_MASK) it returns NULL and everything
gets allocated (unless !gpio_flags as well). What you wanted to remove
is the allocation code, not error handling code. It is always run when
the trigger is set from "none" to something else.

  Daniel

-- 
Dipl.-Math. Daniel Glöckner, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax -11, Bahnhofsallee 1b, 37081 Göttingen, Germany
Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
Geschäftsführer: Dr. Uwe Kracke, Ust-IdNr.: DE 205 198 055

emlix - your embedded linux partner

Re: [patch] gpio: potential null dereference

[Dan Carpenter]

On Tue, Apr 27, 2010 at 11:41:16AM +0200, Daniel Glöckner wrote:
> It returns a valid pointer iff (desc->flags & GPIO_TRIGGER_MASK).
> 
> When !(desc->flags & GPIO_TRIGGER_MASK) it returns NULL and everything
> gets allocated (unless !gpio_flags as well). What you wanted to remove
> is the allocation code, not error handling code. 

No no.  I don't want to remove anything.  I'm happy with the code as is
now that you've explained it to me.  :)

regards,
dan carpenter

> It is always run when
> the trigger is set from "none" to something else.
> 
>   Daniel
>
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Re: [patch] gpio: potential null dereference

[Dan Carpenter]

On Tue, Apr 27, 2010 at 11:41:16AM +0200, Daniel Glöckner wrote:
> It returns a valid pointer iff (desc->flags & GPIO_TRIGGER_MASK).
> 
> When !(desc->flags & GPIO_TRIGGER_MASK) it returns NULL and everything
> gets allocated (unless !gpio_flags as well). What you wanted to remove
> is the allocation code, not error handling code. 

No no.  I don't want to remove anything.  I'm happy with the code as is
now that you've explained it to me.  :)

regards,
dan carpenter

> It is always run when
> the trigger is set from "none" to something else.
> 
>   Daniel
>