Checks for NULL pointers to prevent kernel oops when a USB DAQ

device is plugged out while communicating to a userspace program.

diff --git a/comedi/comedi_fops.c b/comedi/comedi_fops.c
index 97cd1d72081d4103e51d894769c6ab699ee1dd63..e46c7c4bac097f86930d78869d53c10cd9eb79e3 100644 (file)
--- a/comedi/comedi_fops.c
+++ b/comedi/comedi_fops.c
@@ -158,8 +158,9 @@ static int comedi_ioctl(struct inode *inode, struct file *file,
        comedi_device *dev;
        int rc;
 
-       if(dev_file_info == NULL || dev_file_info->device == NULL) return -ENODEV;
+       if (dev_file_info == NULL) return -ENODEV;
        dev = dev_file_info->device;
+       if (dev == NULL) return -ENODEV;
 
        mutex_lock(&dev->mutex);
 
@@ -1503,8 +1504,6 @@ static struct vm_operations_struct comedi_vm_ops = {
 static int comedi_mmap(struct file *file, struct vm_area_struct *vma)
 {
        const unsigned minor = iminor(file->f_dentry->d_inode);
-       struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
-       comedi_device *dev = dev_file_info->device;
        comedi_async *async = NULL;
        unsigned long start = vma->vm_start;
        unsigned long size;
@@ -1512,6 +1511,11 @@ static int comedi_mmap(struct file *file, struct vm_area_struct *vma)
        int i;
        int retval;
        comedi_subdevice *s;
+       struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
+       comedi_device *dev;
+       if (dev_file_info==NULL) return -ENODEV;
+       dev = dev_file_info->device;
+       if (dev==NULL) return -ENODEV;
 
        mutex_lock(&dev->mutex);
        if (!dev->attached) {
@@ -1577,10 +1581,13 @@ static unsigned int comedi_poll(struct file *file, poll_table * wait)
 {
        unsigned int mask = 0;
        const unsigned minor = iminor(file->f_dentry->d_inode);
-       struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
-       comedi_device *dev = dev_file_info->device;
        comedi_subdevice *read_subdev;
        comedi_subdevice *write_subdev;
+       struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
+       comedi_device *dev;
+       if (dev_file_info==NULL) return -ENODEV;
+       dev = dev_file_info->device;
+       if (dev==NULL) return -ENODEV;
 
        mutex_lock(&dev->mutex);
        if (!dev->attached) {
@@ -1626,7 +1633,10 @@ static ssize_t comedi_write(struct file *file, const char *buf, size_t nbytes,
        DECLARE_WAITQUEUE(wait, current);
        const unsigned minor = iminor(file->f_dentry->d_inode);
        struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
-       comedi_device *dev = dev_file_info->device;
+       comedi_device *dev;
+       if (dev_file_info==NULL) return -ENODEV;
+       dev = dev_file_info->device;
+       if (dev==NULL) return -ENODEV;
 
        if (!dev->attached) {
                DPRINTK("no driver configured on comedi%i\n", dev->minor);
@@ -1733,7 +1743,10 @@ static ssize_t comedi_read(struct file *file, char *buf, size_t nbytes,
        DECLARE_WAITQUEUE(wait, current);
        const unsigned minor = iminor(file->f_dentry->d_inode);
        struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
-       comedi_device *dev = dev_file_info->device;
+       comedi_device *dev;
+       if (dev_file_info==NULL) return -ENODEV;
+       dev = dev_file_info->device;
+       if (dev==NULL) return -ENODEV;
 
        if (!dev->attached) {
                DPRINTK("no driver configured on comedi%i\n", dev->minor);
@@ -1937,10 +1950,13 @@ ok:
 static int comedi_close(struct inode *inode, struct file *file)
 {
        const unsigned minor = iminor(inode);
-       struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
-       comedi_device *dev = dev_file_info->device;
        comedi_subdevice *s = NULL;
        int i;
+       struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
+       comedi_device *dev;
+       if (dev_file_info==NULL) return -ENODEV;
+       dev = dev_file_info->device;
+       if (dev==NULL) return -ENODEV;
 
        mutex_lock(&dev->mutex);
 
@@ -1980,7 +1996,10 @@ static int comedi_fasync(int fd, struct file *file, int on)
 {
        const unsigned minor = iminor(file->f_dentry->d_inode);
        struct comedi_device_file_info *dev_file_info = comedi_get_device_file_info(minor);
-       comedi_device *dev = dev_file_info->device;
+       comedi_device *dev;
+       if (dev_file_info==NULL) return -ENODEV;
+       dev = dev_file_info->device;
+       if (dev==NULL) return -ENODEV;
 
        return fasync_helper(fd, file, on, &dev->async_queue);
 }