[PATCH 2/3] usb: max3421-hcd: Fix crash on the driver removal

From: Alexander Amelkin
Date: Fri May 26 2017 - 07:31:07 EST

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NOTE:
Please don't use the plain text here as a patch because it most probably is corrupted by my webmail client.
Attached is a copy of the following text guaranteed to have correct tabs/spaces.
-------------------------
From 8c4c65d3892df3721474023836216a02e03fb23e Mon Sep 17 00:00:00 2001
From: Alexander Amelkin <amelkin@xxxxxxxxxx>
Date: Fri, 14 Apr 2017 17:58:07 +0300
Subject: [PATCH 2/3] usb: max3421-hcd: Fix crash on the driver removal

The driver was calling kthread_stop inside a spin-locked
region while the thread was calling schedule() on a regular
basis. That resulted in panic due to 'scheduling while atomic'.

There was no need to get the spin-lock before stopping the
thread as thread stopping is asynchronous and the thread
only stops when it detects the stop flag set by kthread_stop(),
at which point it is not accessing any resources anyway.

Hence, this patch removes the spin-locking around the
kthread_stop() call.

Additionally, the allocated resources were not free'd in
the correct order. Some were not free'd at all. This patch
switches all resource allocations to devm_* functions
and also reorders deallocation to properly revert the
allocations (although not actually needed for devm-allocated
resources).

Signed-off-by: Alexander Amelkin <alexander@xxxxxxxxxxxxxx>
---
drivers/usb/host/max3421-hcd.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/host/max3421-hcd.c b/drivers/usb/host/max3421-hcd.c
index f600052..bd59c16 100644
--- a/drivers/usb/host/max3421-hcd.c
+++ b/drivers/usb/host/max3421-hcd.c
@@ -1925,10 +1925,10 @@ max3421_probe(struct spi_device *spi)
max3421_hcd_list = max3421_hcd;
INIT_LIST_HEAD(&max3421_hcd->ep_list);

- max3421_hcd->tx = kmalloc(sizeof(*max3421_hcd->tx), GFP_KERNEL);
+ max3421_hcd->tx = devm_kzalloc(&spi->dev, sizeof(*max3421_hcd->tx), GFP_KERNEL);
if (!max3421_hcd->tx)
goto error;
- max3421_hcd->rx = kmalloc(sizeof(*max3421_hcd->rx), GFP_KERNEL);
+ max3421_hcd->rx = devm_kzalloc(&spi->dev, sizeof(*max3421_hcd->rx), GFP_KERNEL);
if (!max3421_hcd->rx)
goto error;

@@ -1946,8 +1946,8 @@ max3421_probe(struct spi_device *spi)
goto error;
}

- retval = request_irq(spi->irq, max3421_irq_handler,
- IRQF_TRIGGER_LOW, "max3421", hcd);
+ retval = devm_request_irq(&spi->dev, spi->irq, max3421_irq_handler,
+ IRQF_TRIGGER_LOW, "max3421", hcd);
if (retval < 0) {
dev_err(&spi->dev, "failed to request irq %d\n", spi->irq);
goto error;
@@ -1976,7 +1976,6 @@ max3421_remove(struct spi_device *spi)
{
struct max3421_hcd *max3421_hcd = NULL, **prev;
struct usb_hcd *hcd = NULL;
- unsigned long flags;

for (prev = &max3421_hcd_list; *prev; prev = &(*prev)->next) {
max3421_hcd = *prev;
@@ -1990,12 +1989,20 @@ max3421_remove(struct spi_device *spi)
spi);
return -ENODEV;
}
- spin_lock_irqsave(&max3421_hcd->lock, flags);
+
+ devm_free_irq(&spi->dev, spi->irq, hcd);
+
+ usb_remove_hcd(hcd);

kthread_stop(max3421_hcd->spi_thread);
- *prev = max3421_hcd->next;

- spin_unlock_irqrestore(&max3421_hcd->lock, flags);
+ devm_kfree(&spi->dev, max3421_hcd->rx);
+ max3421_hcd->rx = NULL;
+ devm_kfree(&spi->dev, max3421_hcd->tx);
+ max3421_hcd->tx = NULL;
+
+ *prev = max3421_hcd->next;
+ usb_put_hcd(hcd);

#if defined(CONFIG_OF)
if (spi->dev.platform_data) {
@@ -2005,12 +2012,6 @@ max3421_remove(struct spi_device *spi)
}
#endif

- free_irq(spi->irq, hcd);
-
- usb_remove_hcd(hcd);
-
-
- usb_put_hcd(hcd);
return 0;
}

--
2.7.4

From 8c4c65d3892df3721474023836216a02e03fb23e Mon Sep 17 00:00:00 2001
From: Alexander Amelkin <amelkin@xxxxxxxxxx>
Date: Fri, 14 Apr 2017 17:58:07 +0300
Subject: [PATCH 2/3] usb: max3421-hcd: Fix crash on the driver removal

The driver was calling kthread_stop inside a spin-locked
region while the thread was calling schedule() on a regular
basis. That resulted in panic due to 'scheduling while atomic'.

There was no need to get the spin-lock before stopping the
thread as thread stopping is asynchronous and the thread
only stops when it detects the stop flag set by kthread_stop(),
at which point it is not accessing any resources anyway.

Hence, this patch removes the spin-locking around the
kthread_stop() call.

Additionally, the allocated resources were not free'd in
the correct order. Some were not free'd at all. This patch
switches all resource allocations to devm_* functions
and also reorders deallocation to properly revert the
allocations (although not actually needed for devm-allocated
resources).

Signed-off-by: Alexander Amelkin <alexander@xxxxxxxxxxxxxx>
---
drivers/usb/host/max3421-hcd.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/host/max3421-hcd.c b/drivers/usb/host/max3421-hcd.c
index f600052..bd59c16 100644
--- a/drivers/usb/host/max3421-hcd.c
+++ b/drivers/usb/host/max3421-hcd.c
@@ -1925,10 +1925,10 @@ max3421_probe(struct spi_device *spi)
max3421_hcd_list = max3421_hcd;
INIT_LIST_HEAD(&max3421_hcd->ep_list);

- max3421_hcd->tx = kmalloc(sizeof(*max3421_hcd->tx), GFP_KERNEL);
+ max3421_hcd->tx = devm_kzalloc(&spi->dev, sizeof(*max3421_hcd->tx), GFP_KERNEL);
if (!max3421_hcd->tx)
goto error;
- max3421_hcd->rx = kmalloc(sizeof(*max3421_hcd->rx), GFP_KERNEL);
+ max3421_hcd->rx = devm_kzalloc(&spi->dev, sizeof(*max3421_hcd->rx), GFP_KERNEL);
if (!max3421_hcd->rx)
goto error;

@@ -1946,8 +1946,8 @@ max3421_probe(struct spi_device *spi)
goto error;
}

- retval = request_irq(spi->irq, max3421_irq_handler,
- IRQF_TRIGGER_LOW, "max3421", hcd);
+ retval = devm_request_irq(&spi->dev, spi->irq, max3421_irq_handler,
+ IRQF_TRIGGER_LOW, "max3421", hcd);
if (retval < 0) {
dev_err(&spi->dev, "failed to request irq %d\n", spi->irq);
goto error;
@@ -1976,7 +1976,6 @@ max3421_remove(struct spi_device *spi)
{
struct max3421_hcd *max3421_hcd = NULL, **prev;
struct usb_hcd *hcd = NULL;
- unsigned long flags;

for (prev = &max3421_hcd_list; *prev; prev = &(*prev)->next) {
max3421_hcd = *prev;
@@ -1990,12 +1989,20 @@ max3421_remove(struct spi_device *spi)
spi);
return -ENODEV;
}
- spin_lock_irqsave(&max3421_hcd->lock, flags);
+
+ devm_free_irq(&spi->dev, spi->irq, hcd);
+
+ usb_remove_hcd(hcd);

kthread_stop(max3421_hcd->spi_thread);
- *prev = max3421_hcd->next;

- spin_unlock_irqrestore(&max3421_hcd->lock, flags);
+ devm_kfree(&spi->dev, max3421_hcd->rx);
+ max3421_hcd->rx = NULL;
+ devm_kfree(&spi->dev, max3421_hcd->tx);
+ max3421_hcd->tx = NULL;
+
+ *prev = max3421_hcd->next;
+ usb_put_hcd(hcd);

#if defined(CONFIG_OF)
if (spi->dev.platform_data) {
@@ -2005,12 +2012,6 @@ max3421_remove(struct spi_device *spi)
}
#endif

- free_irq(spi->irq, hcd);
-
- usb_remove_hcd(hcd);
-
-
- usb_put_hcd(hcd);
return 0;
}

--
2.7.4

Next message: Alexander Amelkin: "[PATCH 3/3] usb: max3421-hcd: Remove function name from dev_dbg calls"
Previous message: Oliver Freyermuth: "Memory corruption kernel issue (potentially exploitable), request for help"
In reply to: Rob Herring: "Re: [PATCH 1/3] usb: max3421-hcd: Add devicetree support to the driver"
Next in thread: Alexander Amelkin: "[PATCH 3/3] usb: max3421-hcd: Remove function name from dev_dbg calls"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]