[PATCH 1/3] spi: fix use-after-free at controller deregistration

[PATCH 1/3] spi: fix use-after-free at controller deregistration

[Johan Hovold]

The controller is typically freed as part of device_unregister() so
store the bus id before deregistration to avoid use-after-free when the
id is later released.

Fixes: 9b61e302210e ("spi: Pick spi bus number from Linux idr or spi alias")
Cc: stable <stable@vger.kernel.org>     # 4.13
Cc: Suniel Mahesh <sunil.m@techveda.org>
Cc: Karthik Tummala <karthik@techveda.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/spi/spi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index e8b5a5e21b2e..3ff0ee88c467 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2245,11 +2245,12 @@ static int __unregister(struct device *dev, void *null)
 void spi_unregister_controller(struct spi_controller *ctlr)
 {
 	struct spi_controller *found;
+	int id = ctlr->bus_num;
 	int dummy;
 
 	/* First make sure that this controller was ever added */
 	mutex_lock(&board_lock);
-	found = idr_find(&spi_master_idr, ctlr->bus_num);
+	found = idr_find(&spi_master_idr, id);
 	mutex_unlock(&board_lock);
 	if (found != ctlr) {
 		dev_dbg(&ctlr->dev,
@@ -2269,7 +2270,7 @@ void spi_unregister_controller(struct spi_controller *ctlr)
 	device_unregister(&ctlr->dev);
 	/* free bus id */
 	mutex_lock(&board_lock);
-	idr_remove(&spi_master_idr, ctlr->bus_num);
+	idr_remove(&spi_master_idr, id);
 	mutex_unlock(&board_lock);
 }
 EXPORT_SYMBOL_GPL(spi_unregister_controller);
-- 
2.14.3

[PATCH 2/3] spi: document odd controller reference handling

[Johan Hovold]

Document the fact that a reference to the controller is dropped as part
of deregistration.

This is an odd pattern as the reference is typically taken in
__spi_alloc_controller() rather than spi_register_controller(). Most
controller drivers gets it right these days and notably the
device-managed interface relies on this behaviour.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/spi/spi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 3ff0ee88c467..b33a727a0158 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2200,7 +2200,7 @@ static void devm_spi_unregister(struct device *dev, void *res)
  * Context: can sleep
  *
  * Register a SPI device as with spi_register_controller() which will
- * automatically be unregister
+ * automatically be unregistered and freed.
  *
  * Return: zero on success, else a negative error code.
  */
@@ -2241,6 +2241,8 @@ static int __unregister(struct device *dev, void *null)
  * only ones directly touching chip registers.
  *
  * This must be called from context that can sleep.
+ *
+ * Note that this function also drops a reference to the controller.
  */
 void spi_unregister_controller(struct spi_controller *ctlr)
 {
-- 
2.14.3

[PATCH 2/3] spi: document odd controller reference handling

[Johan Hovold]

Document the fact that a reference to the controller is dropped as part
of deregistration.

This is an odd pattern as the reference is typically taken in
__spi_alloc_controller() rather than spi_register_controller(). Most
controller drivers gets it right these days and notably the
device-managed interface relies on this behaviour.

Signed-off-by: Johan Hovold <johan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 drivers/spi/spi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 3ff0ee88c467..b33a727a0158 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2200,7 +2200,7 @@ static void devm_spi_unregister(struct device *dev, void *res)
  * Context: can sleep
  *
  * Register a SPI device as with spi_register_controller() which will
- * automatically be unregister
+ * automatically be unregistered and freed.
  *
  * Return: zero on success, else a negative error code.
  */
@@ -2241,6 +2241,8 @@ static int __unregister(struct device *dev, void *null)
  * only ones directly touching chip registers.
  *
  * This must be called from context that can sleep.
+ *
+ * Note that this function also drops a reference to the controller.
  */
 void spi_unregister_controller(struct spi_controller *ctlr)
 {
-- 
2.14.3

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Applied "spi: document odd controller reference handling" to the spi tree

[Mark Brown]

The patch

   spi: document odd controller reference handling

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 68b892f1fdc493d7cd4e4067596879cd097c1f62 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Mon, 30 Oct 2017 11:35:26 +0100
Subject: [PATCH] spi: document odd controller reference handling

Document the fact that a reference to the controller is dropped as part
of deregistration.

This is an odd pattern as the reference is typically taken in
__spi_alloc_controller() rather than spi_register_controller(). Most
controller drivers gets it right these days and notably the
device-managed interface relies on this behaviour.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 6e65524cbfd9..5673cca1d1d0 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2195,7 +2195,7 @@ static void devm_spi_unregister(struct device *dev, void *res)
  * Context: can sleep
  *
  * Register a SPI device as with spi_register_controller() which will
- * automatically be unregister
+ * automatically be unregistered and freed.
  *
  * Return: zero on success, else a negative error code.
  */
@@ -2236,6 +2236,8 @@ static int __unregister(struct device *dev, void *null)
  * only ones directly touching chip registers.
  *
  * This must be called from context that can sleep.
+ *
+ * Note that this function also drops a reference to the controller.
  */
 void spi_unregister_controller(struct spi_controller *ctlr)
 {
-- 
2.15.0.rc2

[PATCH 3/3] spi: spi-axi: take extra controller reference before deregistration

[Johan Hovold]

Take an extra reference to the controller to avoid use-after-free in
free_irq() which is called only after the controller has been
deregistered and freed.

Note that this is not an issue for this particular driver which does not
use shared interrupts, but free_irq() could otherwise end up accessing
the freed controller when CONFIG_DEBUG_SHIRQ is set.

Defer controller release until free_irq() returns to prevent this
from ever becoming an issue should this code be replicated in other
drivers.

Cc: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/spi/spi-axi-spi-engine.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
index 6ab4c7700228..68cfc351b47f 100644
--- a/drivers/spi/spi-axi-spi-engine.c
+++ b/drivers/spi/spi-axi-spi-engine.c
@@ -553,7 +553,7 @@ static int spi_engine_probe(struct platform_device *pdev)
 
 static int spi_engine_remove(struct platform_device *pdev)
 {
-	struct spi_master *master = platform_get_drvdata(pdev);
+	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
 	struct spi_engine *spi_engine = spi_master_get_devdata(master);
 	int irq = platform_get_irq(pdev, 0);
 
@@ -561,6 +561,8 @@ static int spi_engine_remove(struct platform_device *pdev)
 
 	free_irq(irq, master);
 
+	spi_master_put(master);
+
 	writel_relaxed(0xff, spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
 	writel_relaxed(0x00, spi_engine->base + SPI_ENGINE_REG_INT_ENABLE);
 	writel_relaxed(0x01, spi_engine->base + SPI_ENGINE_REG_RESET);
-- 
2.14.3

Re: [PATCH 3/3] spi: spi-axi: take extra controller reference before deregistration

[Lars-Peter Clausen]

On 10/29/2017 12:56 PM, Johan Hovold wrote:
> Take an extra reference to the controller to avoid use-after-free in
> free_irq() which is called only after the controller has been
> deregistered and freed.
> 
> Note that this is not an issue for this particular driver which does not
> use shared interrupts, but free_irq() could otherwise end up accessing
> the freed controller when CONFIG_DEBUG_SHIRQ is set.

Strictly speaking there is no guarantee that the IRQ handler does not run
until free_irq() has been called. And since the SPI master is referenced in
the IRQ handler there could be an use-after-free condition. So there is kind
of a real issue here as well. But it should be really really hard to trigger
it unless the hardware misbehaves.

> 
> Defer controller release until free_irq() returns to prevent this
> from ever becoming an issue should this code be replicated in other
> drivers.
> 
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Johan Hovold <johan@kernel.org>

Acked-by: Lars-Peter Clausen <lars@metafoo.de>

Thanks.

Re: [PATCH 3/3] spi: spi-axi: take extra controller reference before deregistration

[Johan Hovold]

On Mon, Oct 30, 2017 at 10:48:23AM +0100, Lars-Peter Clausen wrote:
> On 10/29/2017 12:56 PM, Johan Hovold wrote:
> > Take an extra reference to the controller to avoid use-after-free in
> > free_irq() which is called only after the controller has been
> > deregistered and freed.
> > 
> > Note that this is not an issue for this particular driver which does not
> > use shared interrupts, but free_irq() could otherwise end up accessing
> > the freed controller when CONFIG_DEBUG_SHIRQ is set.
> 
> Strictly speaking there is no guarantee that the IRQ handler does not run
> until free_irq() has been called. And since the SPI master is referenced in
> the IRQ handler there could be an use-after-free condition. So there is kind
> of a real issue here as well. But it should be really really hard to trigger
> it unless the hardware misbehaves.

You're right of course. Let me update the commit message in a v2 of the
series.

> > Defer controller release until free_irq() returns to prevent this
> > from ever becoming an issue should this code be replicated in other
> > drivers.
> > 
> > Cc: Lars-Peter Clausen <lars@metafoo.de>
> > Signed-off-by: Johan Hovold <johan@kernel.org>
> 
> Acked-by: Lars-Peter Clausen <lars@metafoo.de>

Thanks,
Johan

Applied "spi: spi-axi: fix potential use-after-free after deregistration" to the spi tree

[Mark Brown]

The patch

   spi: spi-axi: fix potential use-after-free after deregistration

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 4d5e0689dc9d5640ad46cdfbe1896b74d8df1661 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Mon, 30 Oct 2017 11:35:27 +0100
Subject: [PATCH] spi: spi-axi: fix potential use-after-free after
 deregistration

Take an extra reference to the controller before deregistering it to
prevent use-after-free in the interrupt handler in case an interrupt
fires before the line is disabled.

Fixes: b1353d1c1d45 ("spi: Add Analog Devices AXI SPI Engine controller support")
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-axi-spi-engine.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
index 6ab4c7700228..68cfc351b47f 100644
--- a/drivers/spi/spi-axi-spi-engine.c
+++ b/drivers/spi/spi-axi-spi-engine.c
@@ -553,7 +553,7 @@ static int spi_engine_probe(struct platform_device *pdev)
 
 static int spi_engine_remove(struct platform_device *pdev)
 {
-	struct spi_master *master = platform_get_drvdata(pdev);
+	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
 	struct spi_engine *spi_engine = spi_master_get_devdata(master);
 	int irq = platform_get_irq(pdev, 0);
 
@@ -561,6 +561,8 @@ static int spi_engine_remove(struct platform_device *pdev)
 
 	free_irq(irq, master);
 
+	spi_master_put(master);
+
 	writel_relaxed(0xff, spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
 	writel_relaxed(0x00, spi_engine->base + SPI_ENGINE_REG_INT_ENABLE);
 	writel_relaxed(0x01, spi_engine->base + SPI_ENGINE_REG_RESET);
-- 
2.15.0.rc2

Applied "spi: spi-axi: fix potential use-after-free after deregistration" to the spi tree

[Mark Brown]

The patch

   spi: spi-axi: fix potential use-after-free after deregistration

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 4d5e0689dc9d5640ad46cdfbe1896b74d8df1661 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Date: Mon, 30 Oct 2017 11:35:27 +0100
Subject: [PATCH] spi: spi-axi: fix potential use-after-free after
 deregistration

Take an extra reference to the controller before deregistering it to
prevent use-after-free in the interrupt handler in case an interrupt
fires before the line is disabled.

Fixes: b1353d1c1d45 ("spi: Add Analog Devices AXI SPI Engine controller support")
Acked-by: Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>
Signed-off-by: Johan Hovold <johan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Signed-off-by: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 drivers/spi/spi-axi-spi-engine.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
index 6ab4c7700228..68cfc351b47f 100644
--- a/drivers/spi/spi-axi-spi-engine.c
+++ b/drivers/spi/spi-axi-spi-engine.c
@@ -553,7 +553,7 @@ static int spi_engine_probe(struct platform_device *pdev)
 
 static int spi_engine_remove(struct platform_device *pdev)
 {
-	struct spi_master *master = platform_get_drvdata(pdev);
+	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
 	struct spi_engine *spi_engine = spi_master_get_devdata(master);
 	int irq = platform_get_irq(pdev, 0);
 
@@ -561,6 +561,8 @@ static int spi_engine_remove(struct platform_device *pdev)
 
 	free_irq(irq, master);
 
+	spi_master_put(master);
+
 	writel_relaxed(0xff, spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
 	writel_relaxed(0x00, spi_engine->base + SPI_ENGINE_REG_INT_ENABLE);
 	writel_relaxed(0x01, spi_engine->base + SPI_ENGINE_REG_RESET);
-- 
2.15.0.rc2

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Applied "spi: fix use-after-free at controller deregistration" to the spi tree

[Mark Brown]

The patch

   spi: fix use-after-free at controller deregistration

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 67f7b2781fafcc0f52464880154b320fea1ae982 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Mon, 30 Oct 2017 11:35:25 +0100
Subject: [PATCH] spi: fix use-after-free at controller deregistration

The controller is typically freed as part of device_unregister() so
store the bus id before deregistration to avoid use-after-free when the
id is later released.

Fixes: 9b61e302210e ("spi: Pick spi bus number from Linux idr or spi alias")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable <stable@vger.kernel.org>
---
 drivers/spi/spi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 6e65524cbfd9..759c9725495a 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2240,11 +2240,12 @@ static int __unregister(struct device *dev, void *null)
 void spi_unregister_controller(struct spi_controller *ctlr)
 {
 	struct spi_controller *found;
+	int id = ctlr->bus_num;
 	int dummy;
 
 	/* First make sure that this controller was ever added */
 	mutex_lock(&board_lock);
-	found = idr_find(&spi_master_idr, ctlr->bus_num);
+	found = idr_find(&spi_master_idr, id);
 	mutex_unlock(&board_lock);
 	if (found != ctlr) {
 		dev_dbg(&ctlr->dev,
@@ -2264,7 +2265,7 @@ void spi_unregister_controller(struct spi_controller *ctlr)
 	device_unregister(&ctlr->dev);
 	/* free bus id */
 	mutex_lock(&board_lock);
-	idr_remove(&spi_master_idr, ctlr->bus_num);
+	idr_remove(&spi_master_idr, id);
 	mutex_unlock(&board_lock);
 }
 EXPORT_SYMBOL_GPL(spi_unregister_controller);
-- 
2.15.0.rc2