[PATCH 0/3] HID: hid-bigbenff: fixing three crash bugs in a gamepad driver

[PATCH 0/3] HID: hid-bigbenff: fixing three crash bugs in a gamepad driver

[Hanno Zulla]

Hi there,

the hid-bigbenff.c had three bugs causing possible kernel crashes.

The first patch fixes a double free during device removal, which was 
caused by a wrong use of input_ff_create_memless(). The 
"driver-specific data to be passed into play_effect" parameter of 
input_ff_create_memless() would later be freed automatically when the ff 
device is removed. Since the driver also uses the managed resource API, 
it would automatically free the memory of this parameter twice, causing 
a general protection fault moments later.

The second patch fixes the error path after hid_hw_start(), as a call 
to hid_hw_stop() is required in case of an error.

The second patch also removes the hid_hw_close() call during device 
removal, as several other hid device drivers don't call this routine, 
either.

The third patch adds a flag to avoid a race condition when there is 
still scheduled work left (or newly being scheduled) during or after 
device removal, which could cause a kernel crash.

Thanks in advance for your review & kind regards,

Hanno

[PATCH 1/3] HID: hid-bigbenff: fix general protection fault caused by double kfree

[Hanno Zulla]

HID: hid-bigbenff: fix general protection fault caused by double kfree

The struct *bigben was allocated via devm_kzalloc() and then used as a
parameter in input_ff_create_memless(). This caused a double kfree
during removal of the device, since both the managed resource API and
ml_ff_destroy() in drivers/input/ff-memless.c would call kfree() on it.

Signed-off-by: Hanno Zulla <kontakt@hanno.de>
---
 drivers/hid/hid-bigbenff.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
index 3f6abd190df4..f7e85bacb688 100644
--- a/drivers/hid/hid-bigbenff.c
+++ b/drivers/hid/hid-bigbenff.c
@@ -220,10 +220,16 @@ static void bigben_worker(struct work_struct *work)
 static int hid_bigben_play_effect(struct input_dev *dev, void *data,
 			 struct ff_effect *effect)
 {
-	struct bigben_device *bigben = data;
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct bigben_device *bigben = hid_get_drvdata(hid);
 	u8 right_motor_on;
 	u8 left_motor_force;
 
+	if (!bigben) {
+		hid_err(hid, "no device data\n");
+		return 0;
+	}
+
 	if (effect->type != FF_RUMBLE)
 		return 0;
 
@@ -341,7 +347,7 @@ static int bigben_probe(struct hid_device *hid,
 
 	INIT_WORK(&bigben->worker, bigben_worker);
 
-	error = input_ff_create_memless(hidinput->input, bigben,
+	error = input_ff_create_memless(hidinput->input, NULL,
 		hid_bigben_play_effect);
 	if (error)
 		return error;
-- 
2.20.1

[PATCH 2/3] HID: hid-bigbenff: call hid_hw_stop() in case of error

[Hanno Zulla]

[PATCH 2/3] HID: hid-bigbenff: call hid_hw_stop() in case of error

It's required to call hid_hw_stop() once hid_hw_start() was called
previously, so error cases need to handle this. Also, hid_hw_close() is
not necessary during removal.

Signed-off-by: Hanno Zulla <kontakt@hanno.de>
---
 drivers/hid/hid-bigbenff.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
index f7e85bacb688..f8c552b64a89 100644
--- a/drivers/hid/hid-bigbenff.c
+++ b/drivers/hid/hid-bigbenff.c
@@ -305,7 +305,6 @@ static void bigben_remove(struct hid_device *hid)
 	struct bigben_device *bigben = hid_get_drvdata(hid);
 
 	cancel_work_sync(&bigben->worker);
-	hid_hw_close(hid);
 	hid_hw_stop(hid);
 }
 
@@ -350,7 +349,7 @@ static int bigben_probe(struct hid_device *hid,
 	error = input_ff_create_memless(hidinput->input, NULL,
 		hid_bigben_play_effect);
 	if (error)
-		return error;
+		goto error_hw_stop;
 
 	name_sz = strlen(dev_name(&hid->dev)) + strlen(":red:bigben#") + 1;
 
@@ -360,8 +359,10 @@ static int bigben_probe(struct hid_device *hid,
 			sizeof(struct led_classdev) + name_sz,
 			GFP_KERNEL
 		);
-		if (!led)
-			return -ENOMEM;
+		if (!led) {
+			error = -ENOMEM;
+			goto error_hw_stop;
+		}
 		name = (void *)(&led[1]);
 		snprintf(name, name_sz,
 			"%s:red:bigben%d",
@@ -375,7 +376,7 @@ static int bigben_probe(struct hid_device *hid,
 		bigben->leds[n] = led;
 		error = devm_led_classdev_register(&hid->dev, led);
 		if (error)
-			return error;
+			goto error_hw_stop;
 	}
 
 	/* initial state: LED1 is on, no rumble effect */
@@ -389,6 +390,10 @@ static int bigben_probe(struct hid_device *hid,
 	hid_info(hid, "LED and force feedback support for BigBen gamepad\n");
 
 	return 0;
+
+error_hw_stop:
+	hid_hw_stop(hid);
+	return error;
 }
 
 static __u8 *bigben_report_fixup(struct hid_device *hid, __u8 *rdesc,
-- 
2.20.1

[PATCH 3/3] HID: hid-bigbenff: fix race condition for scheduled work during removal

[Hanno Zulla]

HID: hid-bigbenff: fix race condition for scheduled work during removal

It's possible that there is scheduled work left while the device is
already being removed, which can cause a kernel crash. Adding a flag
will avoid this.

Signed-off-by: Hanno Zulla <kontakt@hanno.de>
---
 drivers/hid/hid-bigbenff.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
index f8c552b64a89..db6da21ade06 100644
--- a/drivers/hid/hid-bigbenff.c
+++ b/drivers/hid/hid-bigbenff.c
@@ -174,6 +174,7 @@ static __u8 pid0902_rdesc_fixed[] = {
 struct bigben_device {
 	struct hid_device *hid;
 	struct hid_report *report;
+	bool removed;
 	u8 led_state;         /* LED1 = 1 .. LED4 = 8 */
 	u8 right_motor_on;    /* right motor off/on 0/1 */
 	u8 left_motor_force;  /* left motor force 0-255 */
@@ -190,6 +191,9 @@ static void bigben_worker(struct work_struct *work)
 		struct bigben_device, worker);
 	struct hid_field *report_field = bigben->report->field[0];
 
+	if (bigben->removed)
+		return;
+
 	if (bigben->work_led) {
 		bigben->work_led = false;
 		report_field->value[0] = 0x01; /* 1 = led message */
@@ -304,6 +308,7 @@ static void bigben_remove(struct hid_device *hid)
 {
 	struct bigben_device *bigben = hid_get_drvdata(hid);
 
+	bigben->removed = true;
 	cancel_work_sync(&bigben->worker);
 	hid_hw_stop(hid);
 }
@@ -324,6 +329,7 @@ static int bigben_probe(struct hid_device *hid,
 		return -ENOMEM;
 	hid_set_drvdata(hid, bigben);
 	bigben->hid = hid;
+	bigben->removed = false;
 
 	error = hid_parse(hid);
 	if (error) {
-- 
2.20.1

Re: [PATCH 0/3] HID: hid-bigbenff: fixing three crash bugs in a gamepad driver

[Benjamin Tissoires]

Hi Hanno,

On Mon, Feb 17, 2020 at 4:24 PM Hanno Zulla <abos@hanno.de> wrote:
>
> Hi there,
>
> the hid-bigbenff.c had three bugs causing possible kernel crashes.
>
> The first patch fixes a double free during device removal, which was
> caused by a wrong use of input_ff_create_memless(). The
> "driver-specific data to be passed into play_effect" parameter of
> input_ff_create_memless() would later be freed automatically when the ff
> device is removed. Since the driver also uses the managed resource API,
> it would automatically free the memory of this parameter twice, causing
> a general protection fault moments later.
>
> The second patch fixes the error path after hid_hw_start(), as a call
> to hid_hw_stop() is required in case of an error.
>
> The second patch also removes the hid_hw_close() call during device
> removal, as several other hid device drivers don't call this routine,
> either.
>
> The third patch adds a flag to avoid a race condition when there is
> still scheduled work left (or newly being scheduled) during or after
> device removal, which could cause a kernel crash.
>
> Thanks in advance for your review & kind regards,
>

I think the patches are correct (have you tested them with actual HW?).
However, checkpatch complains that the From and Signed-off-by email
differ. Can you send a v2 with a fix for that?

Cheers,
Benjamin

[PATCH v2 0/3] HID: hid-bigbenff: fixing three crash bugs in a gamepad driver

[Hanno Zulla]

Hi Benjamin,

> I think the patches are correct (have you tested them with actual HW?).

Yes, I did, and am also properly embarrassed that I didn't notice the 
double free bug in the original driver.

> However, checkpatch complains that the From and Signed-off-by email
> differ. Can you send a v2 with a fix for that?

Here it is.

Thanks,

Hanno

[PATCH v2 1/3] HID: hid-bigbenff: fix general protection fault caused by double kfree

[Hanno Zulla]

HID: hid-bigbenff: fix general protection fault caused by double kfree

The struct *bigben was allocated via devm_kzalloc() and then used as a
parameter in input_ff_create_memless(). This caused a double kfree
during removal of the device, since both the managed resource API and
ml_ff_destroy() in drivers/input/ff-memless.c would call kfree() on it.

Signed-off-by: Hanno Zulla <kontakt@hanno.de>
---
 drivers/hid/hid-bigbenff.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
index 3f6abd190df4..f7e85bacb688 100644
--- a/drivers/hid/hid-bigbenff.c
+++ b/drivers/hid/hid-bigbenff.c
@@ -220,10 +220,16 @@ static void bigben_worker(struct work_struct *work)
 static int hid_bigben_play_effect(struct input_dev *dev, void *data,
 			 struct ff_effect *effect)
 {
-	struct bigben_device *bigben = data;
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct bigben_device *bigben = hid_get_drvdata(hid);
 	u8 right_motor_on;
 	u8 left_motor_force;
 
+	if (!bigben) {
+		hid_err(hid, "no device data\n");
+		return 0;
+	}
+
 	if (effect->type != FF_RUMBLE)
 		return 0;
 
@@ -341,7 +347,7 @@ static int bigben_probe(struct hid_device *hid,
 
 	INIT_WORK(&bigben->worker, bigben_worker);
 
-	error = input_ff_create_memless(hidinput->input, bigben,
+	error = input_ff_create_memless(hidinput->input, NULL,
 		hid_bigben_play_effect);
 	if (error)
 		return error;
-- 
2.20.1

[PATCH v2 2/3] HID: hid-bigbenff: call hid_hw_stop() in case of error

[Hanno Zulla]

HID: hid-bigbenff: call hid_hw_stop() in case of error

It's required to call hid_hw_stop() once hid_hw_start() was called
previously, so error cases need to handle this. Also, hid_hw_close() is
not necessary during removal.

Signed-off-by: Hanno Zulla <kontakt@hanno.de>
---
 drivers/hid/hid-bigbenff.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
index f7e85bacb688..f8c552b64a89 100644
--- a/drivers/hid/hid-bigbenff.c
+++ b/drivers/hid/hid-bigbenff.c
@@ -305,7 +305,6 @@ static void bigben_remove(struct hid_device *hid)
 	struct bigben_device *bigben = hid_get_drvdata(hid);
 
 	cancel_work_sync(&bigben->worker);
-	hid_hw_close(hid);
 	hid_hw_stop(hid);
 }
 
@@ -350,7 +349,7 @@ static int bigben_probe(struct hid_device *hid,
 	error = input_ff_create_memless(hidinput->input, NULL,
 		hid_bigben_play_effect);
 	if (error)
-		return error;
+		goto error_hw_stop;
 
 	name_sz = strlen(dev_name(&hid->dev)) + strlen(":red:bigben#") + 1;
 
@@ -360,8 +359,10 @@ static int bigben_probe(struct hid_device *hid,
 			sizeof(struct led_classdev) + name_sz,
 			GFP_KERNEL
 		);
-		if (!led)
-			return -ENOMEM;
+		if (!led) {
+			error = -ENOMEM;
+			goto error_hw_stop;
+		}
 		name = (void *)(&led[1]);
 		snprintf(name, name_sz,
 			"%s:red:bigben%d",
@@ -375,7 +376,7 @@ static int bigben_probe(struct hid_device *hid,
 		bigben->leds[n] = led;
 		error = devm_led_classdev_register(&hid->dev, led);
 		if (error)
-			return error;
+			goto error_hw_stop;
 	}
 
 	/* initial state: LED1 is on, no rumble effect */
@@ -389,6 +390,10 @@ static int bigben_probe(struct hid_device *hid,
 	hid_info(hid, "LED and force feedback support for BigBen gamepad\n");
 
 	return 0;
+
+error_hw_stop:
+	hid_hw_stop(hid);
+	return error;
 }
 
 static __u8 *bigben_report_fixup(struct hid_device *hid, __u8 *rdesc,
-- 
2.20.1

[PATCH v2 3/3] HID: hid-bigbenff: fix race condition for scheduled work during removal

[Hanno Zulla]

HID: hid-bigbenff: fix race condition for scheduled work during removal

It's possible that there is scheduled work left while the device is
already being removed, which can cause a kernel crash. Adding a flag
will avoid this.

Signed-off-by: Hanno Zulla <kontakt@hanno.de>
---
 drivers/hid/hid-bigbenff.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
index f8c552b64a89..db6da21ade06 100644
--- a/drivers/hid/hid-bigbenff.c
+++ b/drivers/hid/hid-bigbenff.c
@@ -174,6 +174,7 @@ static __u8 pid0902_rdesc_fixed[] = {
 struct bigben_device {
 	struct hid_device *hid;
 	struct hid_report *report;
+	bool removed;
 	u8 led_state;         /* LED1 = 1 .. LED4 = 8 */
 	u8 right_motor_on;    /* right motor off/on 0/1 */
 	u8 left_motor_force;  /* left motor force 0-255 */
@@ -190,6 +191,9 @@ static void bigben_worker(struct work_struct *work)
 		struct bigben_device, worker);
 	struct hid_field *report_field = bigben->report->field[0];
 
+	if (bigben->removed)
+		return;
+
 	if (bigben->work_led) {
 		bigben->work_led = false;
 		report_field->value[0] = 0x01; /* 1 = led message */
@@ -304,6 +308,7 @@ static void bigben_remove(struct hid_device *hid)
 {
 	struct bigben_device *bigben = hid_get_drvdata(hid);
 
+	bigben->removed = true;
 	cancel_work_sync(&bigben->worker);
 	hid_hw_stop(hid);
 }
@@ -324,6 +329,7 @@ static int bigben_probe(struct hid_device *hid,
 		return -ENOMEM;
 	hid_set_drvdata(hid, bigben);
 	bigben->hid = hid;
+	bigben->removed = false;
 
 	error = hid_parse(hid);
 	if (error) {
-- 
2.20.1

Re: [PATCH v2 0/3] HID: hid-bigbenff: fixing three crash bugs in a gamepad driver

[Benjamin Tissoires]

On Tue, Feb 18, 2020 at 12:44 PM Hanno Zulla <kontakt@hanno.de> wrote:
>
> Hi Benjamin,
>
> > I think the patches are correct (have you tested them with actual HW?).
>
> Yes, I did, and am also properly embarrassed that I didn't notice the
> double free bug in the original driver.
>
> > However, checkpatch complains that the From and Signed-off-by email
> > differ. Can you send a v2 with a fix for that?
>
> Here it is.
>

Thanks for the quick respin.

Not sure what happened, but the commit title was duplicated in all of
the commits.

Anyway, not a big deal, fixed and pushed to for-5.6/upstream-fixes

Cheers,
Benjamin

> Thanks,
>
> Hanno
>