Commit 543af586 authored by Xiubo Li's avatar Xiubo Li Committed by Greg Kroah-Hartman
Browse files

uio: change to use the mutex lock instead of the spin lock 



We are hitting a regression with the following commit:

commit a93e7b33
Author: Hamish Martin <hamish.martin@alliedtelesis.co.nz>
Date:   Mon May 14 13:32:23 2018 +1200

    uio: Prevent device destruction while fds are open

The problem is the addition of spin_lock_irqsave in uio_write. This
leads to hitting  uio_write -> copy_from_user -> _copy_from_user ->
might_fault and the logs filling up with sleeping warnings.

I also noticed some uio drivers allocate memory, sleep, grab mutexes
from callouts like open() and release and uio is now doing
spin_lock_irqsave while calling them.

Reported-by: default avatarMike Christie <mchristi@redhat.com>
CC: Hamish Martin <hamish.martin@alliedtelesis.co.nz>
Reviewed-by: default avatarHamish Martin <hamish.martin@alliedtelesis.co.nz>
Signed-off-by: default avatarXiubo Li <xiubli@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9421e45f

drivers/uio/uio.c

+13 −19
Original line number Diff line number Diff line
@@ -433,7 +433,6 @@ static int uio_open(struct inode *inode, struct file *filep) 
	struct uio_device *idev;

	struct uio_listener *listener;

	int ret = 0;

	unsigned long flags;



	mutex_lock(&minor_lock);

	idev = idr_find(&uio_idr, iminor(inode));
@@ -460,10 +459,10 @@ static int uio_open(struct inode *inode, struct file *filep) 
	listener->event_count = atomic_read(&idev->event);

	filep->private_data = listener;



	spin_lock_irqsave(&idev->info_lock, flags);

	mutex_lock(&idev->info_lock);

	if (idev->info && idev->info->open)

		ret = idev->info->open(idev->info, inode);

	spin_unlock_irqrestore(&idev->info_lock, flags);

	mutex_unlock(&idev->info_lock);

	if (ret)

		goto err_infoopen;
@@ -495,12 +494,11 @@ static int uio_release(struct inode *inode, struct file *filep) 
	int ret = 0;

	struct uio_listener *listener = filep->private_data;

	struct uio_device *idev = listener->dev;

	unsigned long flags;



	spin_lock_irqsave(&idev->info_lock, flags);

	mutex_lock(&idev->info_lock);

	if (idev->info && idev->info->release)

		ret = idev->info->release(idev->info, inode);

	spin_unlock_irqrestore(&idev->info_lock, flags);

	mutex_unlock(&idev->info_lock);



	module_put(idev->owner);

	kfree(listener);
@@ -513,12 +511,11 @@ static __poll_t uio_poll(struct file *filep, poll_table *wait) 
	struct uio_listener *listener = filep->private_data;

	struct uio_device *idev = listener->dev;

	__poll_t ret = 0;

	unsigned long flags;



	spin_lock_irqsave(&idev->info_lock, flags);

	mutex_lock(&idev->info_lock);

	if (!idev->info || !idev->info->irq)

		ret = -EIO;

	spin_unlock_irqrestore(&idev->info_lock, flags);

	mutex_unlock(&idev->info_lock);



	if (ret)

		return ret;
@@ -537,12 +534,11 @@ static ssize_t uio_read(struct file *filep, char __user *buf, 
	DECLARE_WAITQUEUE(wait, current);

	ssize_t retval = 0;

	s32 event_count;

	unsigned long flags;



	spin_lock_irqsave(&idev->info_lock, flags);

	mutex_lock(&idev->info_lock);

	if (!idev->info || !idev->info->irq)

		retval = -EIO;

	spin_unlock_irqrestore(&idev->info_lock, flags);

	mutex_unlock(&idev->info_lock);



	if (retval)

		return retval;
@@ -592,9 +588,8 @@ static ssize_t uio_write(struct file *filep, const char __user *buf, 
	struct uio_device *idev = listener->dev;

	ssize_t retval;

	s32 irq_on;

	unsigned long flags;



	spin_lock_irqsave(&idev->info_lock, flags);

	mutex_lock(&idev->info_lock);

	if (!idev->info || !idev->info->irq) {

		retval = -EIO;

		goto out;
@@ -618,7 +613,7 @@ static ssize_t uio_write(struct file *filep, const char __user *buf, 
	retval = idev->info->irqcontrol(idev->info, irq_on);



out:

	spin_unlock_irqrestore(&idev->info_lock, flags);

	mutex_unlock(&idev->info_lock);

	return retval ? retval : sizeof(s32);

}
@@ -865,7 +860,7 @@ int __uio_register_device(struct module *owner, 


	idev->owner = owner;

	idev->info = info;

	spin_lock_init(&idev->info_lock);

	mutex_init(&idev->info_lock);

	init_waitqueue_head(&idev->wait);

	atomic_set(&idev->event, 0);
@@ -929,7 +924,6 @@ EXPORT_SYMBOL_GPL(__uio_register_device); 
void uio_unregister_device(struct uio_info *info)

{

	struct uio_device *idev;

	unsigned long flags;



	if (!info || !info->uio_dev)

		return;
@@ -943,9 +937,9 @@ void uio_unregister_device(struct uio_info *info) 
	if (info->irq && info->irq != UIO_IRQ_CUSTOM)

		free_irq(info->irq, idev);



	spin_lock_irqsave(&idev->info_lock, flags);

	mutex_lock(&idev->info_lock);

	idev->info = NULL;

	spin_unlock_irqrestore(&idev->info_lock, flags);

	mutex_unlock(&idev->info_lock);



	device_unregister(&idev->dev);

include/linux/uio_driver.h

+1 −1
Original line number Diff line number Diff line
@@ -75,7 +75,7 @@ struct uio_device { 
        struct fasync_struct    *async_queue;

        wait_queue_head_t       wait;

        struct uio_info         *info;

	spinlock_t		info_lock;

	struct mutex		info_lock;

        struct kobject          *map_dir;

        struct kobject          *portio_dir;

};

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