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Subject[PATCH] USB: USBHID: Fix race between disconnect and hiddev_ioctl
A USB HID device can be disconnected at any time.
If this happens right before or while hiddev_ioctl is in progress,
the hiddev_ioctl tries to access invalid hiddev->hid pointer.
When the hid device is disconnected, the hiddev_disconnect()
ends up with a call to hid_device_release() which frees
hid_device, but doesn't set the hiddev->hid pointer to NULL.
If the deallocated memory region has been re-used by the kernel,
this can cause a crash or memory corruption.

Since disconnect can happen at any time, we can't initialize
struct hid_device *hid = hiddev->hid at the beginning of ioctl
and then use it.

This change checks hiddev->exist flag while holding
the existancelock and uses hid_device only if it exists.

Signed-off-by: Valentine Barshak <vaxon@black.localdomain>
---
drivers/hid/usbhid/hiddev.c | 168 +++++++++++++++++++++++++++++++++----------
1 files changed, 131 insertions(+), 37 deletions(-)
diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 984feb3..cbb6974 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -585,7 +585,7 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct hiddev_list *list = file->private_data;
struct hiddev *hiddev = list->hiddev;
- struct hid_device *hid = hiddev->hid;
+ struct hid_device *hid;
struct usb_device *dev;
struct hiddev_collection_info cinfo;
struct hiddev_report_info rinfo;
@@ -593,26 +593,33 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
struct hiddev_devinfo dinfo;
struct hid_report *report;
struct hid_field *field;
- struct usbhid_device *usbhid = hid->driver_data;
+ struct usbhid_device *usbhid;
void __user *user_arg = (void __user *)arg;
int i, r;
-
+
/* Called without BKL by compat methods so no BKL taken */

/* FIXME: Who or what stop this racing with a disconnect ?? */
- if (!hiddev->exist || !hid)
+ if (!hiddev->exist)
return -EIO;

- dev = hid_to_usb_dev(hid);
-
switch (cmd) {

case HIDIOCGVERSION:
return put_user(HID_VERSION, (int __user *)arg);

case HIDIOCAPPLICATION:
- if (arg < 0 || arg >= hid->maxapplication)
- return -EINVAL;
+ mutex_lock(&hiddev->existancelock);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ if (arg < 0 || arg >= hid->maxapplication) {
+ r = -EINVAL;
+ goto ret_unlock;
+ }

for (i = 0; i < hid->maxcollection; i++)
if (hid->collection[i].type ==
@@ -620,11 +627,22 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
break;

if (i == hid->maxcollection)
- return -EINVAL;
-
- return hid->collection[i].usage;
+ r = -EINVAL;
+ else
+ r = hid->collection[i].usage;
+ goto ret_unlock;

case HIDIOCGDEVINFO:
+ mutex_lock(&hiddev->existancelock);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ dev = hid_to_usb_dev(hid);
+ usbhid = hid->driver_data;
+
dinfo.bustype = BUS_USB;
dinfo.busnum = dev->bus->busnum;
dinfo.devnum = dev->devnum;
@@ -633,6 +651,8 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
dinfo.product = le16_to_cpu(dev->descriptor.idProduct);
dinfo.version = le16_to_cpu(dev->descriptor.bcdDevice);
dinfo.num_applications = hid->maxapplication;
+ mutex_unlock(&hiddev->existancelock);
+
if (copy_to_user(user_arg, &dinfo, sizeof(dinfo)))
return -EFAULT;

@@ -666,6 +686,7 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
r = hiddev_ioctl_string(hiddev, cmd, user_arg);
else
r = -ENODEV;
+ret_unlock:
mutex_unlock(&hiddev->existancelock);
return r;

@@ -675,6 +696,7 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
mutex_unlock(&hiddev->existancelock);
return -ENODEV;
}
+ hid = hiddev->hid;
usbhid_init_reports(hid);
mutex_unlock(&hiddev->existancelock);

@@ -687,14 +709,21 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
if (rinfo.report_type == HID_REPORT_TYPE_OUTPUT)
return -EINVAL;

- if ((report = hiddev_lookup_report(hid, &rinfo)) == NULL)
- return -EINVAL;
-
mutex_lock(&hiddev->existancelock);
- if (hiddev->exist) {
- usbhid_submit_report(hid, report, USB_DIR_IN);
- usbhid_wait_io(hid);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ report = hiddev_lookup_report(hid, &rinfo);
+ if (report == NULL) {
+ r = -EINVAL;
+ goto ret_unlock;
}
+
+ usbhid_submit_report(hid, report, USB_DIR_IN);
+ usbhid_wait_io(hid);
mutex_unlock(&hiddev->existancelock);

return 0;
@@ -706,14 +735,21 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
if (rinfo.report_type == HID_REPORT_TYPE_INPUT)
return -EINVAL;

- if ((report = hiddev_lookup_report(hid, &rinfo)) == NULL)
- return -EINVAL;
-
mutex_lock(&hiddev->existancelock);
- if (hiddev->exist) {
- usbhid_submit_report(hid, report, USB_DIR_OUT);
- usbhid_wait_io(hid);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ report = hiddev_lookup_report(hid, &rinfo);
+ if (report == NULL) {
+ r = -EINVAL;
+ goto ret_unlock;
}
+
+ usbhid_submit_report(hid, report, USB_DIR_OUT);
+ usbhid_wait_io(hid);
mutex_unlock(&hiddev->existancelock);

return 0;
@@ -722,10 +758,21 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
if (copy_from_user(&rinfo, user_arg, sizeof(rinfo)))
return -EFAULT;

- if ((report = hiddev_lookup_report(hid, &rinfo)) == NULL)
- return -EINVAL;
+ mutex_lock(&hiddev->existancelock);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ report = hiddev_lookup_report(hid, &rinfo);
+ if (report == NULL) {
+ r = -EINVAL;
+ goto ret_unlock;
+ }

rinfo.num_fields = report->maxfield;
+ mutex_unlock(&hiddev->existancelock);

if (copy_to_user(user_arg, &rinfo, sizeof(rinfo)))
return -EFAULT;
@@ -737,11 +784,23 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
return -EFAULT;
rinfo.report_type = finfo.report_type;
rinfo.report_id = finfo.report_id;
- if ((report = hiddev_lookup_report(hid, &rinfo)) == NULL)
- return -EINVAL;
+ mutex_lock(&hiddev->existancelock);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }

- if (finfo.field_index >= report->maxfield)
- return -EINVAL;
+ hid = hiddev->hid;
+ report = hiddev_lookup_report(hid, &rinfo);
+ if (report == NULL) {
+ r = -EINVAL;
+ goto ret_unlock;
+ }
+
+ if (finfo.field_index >= report->maxfield) {
+ r = -EINVAL;
+ goto ret_unlock;
+ }

field = report->field[finfo.field_index];
memset(&finfo, 0, sizeof(finfo));
@@ -759,6 +818,7 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
finfo.physical_maximum = field->physical_maximum;
finfo.unit_exponent = field->unit_exponent;
finfo.unit = field->unit;
+ mutex_unlock(&hiddev->existancelock);

if (copy_to_user(user_arg, &finfo, sizeof(finfo)))
return -EFAULT;
@@ -784,12 +844,22 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
if (copy_from_user(&cinfo, user_arg, sizeof(cinfo)))
return -EFAULT;

- if (cinfo.index >= hid->maxcollection)
- return -EINVAL;
+ mutex_lock(&hiddev->existancelock);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ if (cinfo.index >= hid->maxcollection) {
+ r = -EINVAL;
+ goto ret_unlock;
+ }

cinfo.type = hid->collection[cinfo.index].type;
cinfo.usage = hid->collection[cinfo.index].usage;
cinfo.level = hid->collection[cinfo.index].level;
+ mutex_lock(&hiddev->existancelock);

if (copy_to_user(user_arg, &cinfo, sizeof(cinfo)))
return -EFAULT;
@@ -802,24 +872,48 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

if (_IOC_NR(cmd) == _IOC_NR(HIDIOCGNAME(0))) {
int len;
- if (!hid->name)
- return 0;
+
+ mutex_lock(&hiddev->existancelock);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ if (!hid->name) {
+ r = 0;
+ goto ret_unlock;
+ }
+
len = strlen(hid->name) + 1;
if (len > _IOC_SIZE(cmd))
len = _IOC_SIZE(cmd);
- return copy_to_user(user_arg, hid->name, len) ?
+ r = copy_to_user(user_arg, hid->name, len) ?
-EFAULT : len;
+ goto ret_unlock;
}

if (_IOC_NR(cmd) == _IOC_NR(HIDIOCGPHYS(0))) {
int len;
- if (!hid->phys)
- return 0;
+
+ mutex_lock(&hiddev->existancelock);
+ if (!hiddev->exist) {
+ r = -ENODEV;
+ goto ret_unlock;
+ }
+
+ hid = hiddev->hid;
+ if (!hid->phys) {
+ r = 0;
+ goto ret_unlock;
+ }
+
len = strlen(hid->phys) + 1;
if (len > _IOC_SIZE(cmd))
len = _IOC_SIZE(cmd);
- return copy_to_user(user_arg, hid->phys, len) ?
+ r = copy_to_user(user_arg, hid->phys, len) ?
-EFAULT : len;
+ goto ret_unlock;
}
}
return -EINVAL;
--
1.6.0.6


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