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

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Message-ID: <365366d9802b5b4ed1ec3a33d0ea0da3@amelkin.msk.ru>
Date:   Fri, 26 May 2017 14:30:56 +0300
From:   Alexander Amelkin <alexander@...lkin.msk.ru>
To:     linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 2/3] usb: max3421-hcd: Fix crash on the driver removal

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@...twel.ru>
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@...lkin.msk.ru>
---
  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


View attachment "0002-usb-max3421-hcd-Fix-crash-on-the-driver-removal.patch" of type "text/x-diff" (3337 bytes)