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USB: fix DoS in pwc USB video driver

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the pwc driver has a disconnect method that waits for user space to
close the device. This opens up an opportunity for a DoS attack,
blocking the USB subsystem and making khubd's task busy wait in
kernel space. This patch shifts freeing resources to close if an opened
device is disconnected.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
CC: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Oliver Neukum 2007-08-21 07:10:42 +02:00 committed by Greg Kroah-Hartman
parent c39772d82a
commit 85237f202d
2 changed files with 36 additions and 17 deletions
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38
drivers/media/video/pwc/pwc-if.c
View file

@ -1196,12 +1196,19 @@ static int pwc_video_open(struct inode *inode, struct file *file)
return 0;
}
static void pwc_cleanup(struct pwc_device *pdev)
{
pwc_remove_sysfs_files(pdev->vdev);
video_unregister_device(pdev->vdev);
}
/* Note that all cleanup is done in the reverse order as in _open */
static int pwc_video_close(struct inode *inode, struct file *file)
{
struct video_device *vdev = file->private_data;
struct pwc_device *pdev;
int i;
int i, hint;
PWC_DEBUG_OPEN(">> video_close called(vdev = 0x%p).\n", vdev);
@ -1224,8 +1231,9 @@ static int pwc_video_close(struct inode *inode, struct file *file)
pwc_isoc_cleanup(pdev);
pwc_free_buffers(pdev);
lock_kernel();
/* Turn off LEDS and power down camera, but only when not unplugged */
if (pdev->error_status != EPIPE) {
if (!pdev->unplugged) {
/* Turn LEDs off */
if (pwc_set_leds(pdev, 0, 0) < 0)
PWC_DEBUG_MODULE("Failed to set LED on/off time.\n");
@ -1234,9 +1242,19 @@ static int pwc_video_close(struct inode *inode, struct file *file)
if (i < 0)
PWC_ERROR("Failed to power down camera (%d)\n", i);
}
}
pdev->vopen--;
PWC_DEBUG_OPEN("<< video_close() vopen=%d\n", pdev->vopen);
PWC_DEBUG_OPEN("<< video_close() vopen=%d\n", i);
} else {
pwc_cleanup(pdev);
/* Free memory (don't set pdev to 0 just yet) */
kfree(pdev);
/* search device_hint[] table if we occupy a slot, by any chance */
for (hint = 0; hint < MAX_DEV_HINTS; hint++)
if (device_hint[hint].pdev == pdev)
device_hint[hint].pdev = NULL;
}
unlock_kernel();
return 0;
}
@ -1791,13 +1809,12 @@ static void usb_pwc_disconnect(struct usb_interface *intf)
/* Alert waiting processes */
wake_up_interruptible(&pdev->frameq);
/* Wait until device is closed */
while (pdev->vopen)
schedule();
/* Device is now closed, so we can safely unregister it */
if(pdev->vopen) {
pdev->unplugged = 1;
} else {
/* Device is closed, so we can safely unregister it */
PWC_DEBUG_PROBE("Unregistering video device in disconnect().\n");
pwc_remove_sysfs_files(pdev->vdev);
video_unregister_device(pdev->vdev);
pwc_cleanup(pdev);
/* Free memory (don't set pdev to 0 just yet) */
kfree(pdev);
@ -1806,6 +1823,7 @@ static void usb_pwc_disconnect(struct usb_interface *intf)
for (hint = 0; hint < MAX_DEV_HINTS; hint++)
if (device_hint[hint].pdev == pdev)
device_hint[hint].pdev = NULL;
}
unlock_kernel();
}

1
drivers/media/video/pwc/pwc.h
View file

@ -193,6 +193,7 @@ struct pwc_device
char vsnapshot; /* snapshot mode */
char vsync; /* used by isoc handler */
char vmirror; /* for ToUCaM series */
char unplugged;
int cmd_len;
unsigned char cmd_buf[13];