USB: fix DoS in pwc USB video driver (CVE-2007-5093)

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.

Adrian Bunk:
Backported to 2.6.16.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Adrian Bunk <bunk@kernel.org>

diff --git a/drivers/usb/media/pwc/pwc-if.c b/drivers/usb/media/pwc/pwc-if.c
index 4f9b0dc6fd7bdd6fd22e71588c23b045c2747ec2..8e55391fe2ec08fbf0fab1d92a98696e3eb62242 100644 (file)
--- a/drivers/usb/media/pwc/pwc-if.c
+++ b/drivers/usb/media/pwc/pwc-if.c
@@ -1100,12 +1100,18 @@ static int pwc_video_open(struct inode *inode, struct file *file)
        return 0;
 }
 
+
+static void pwc_cleanup(struct pwc_device *pdev)
+{
+       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;
 
        Trace(TRACE_OPEN, ">> video_close called(vdev = 0x%p).\n", vdev);
 
@@ -1140,8 +1146,9 @@ 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)
                        Info("Failed to set LED on/off time.\n");
@@ -1150,9 +1157,19 @@ static int pwc_video_close(struct inode *inode, struct file *file)
                        if (i < 0)
                                Err("Failed to power down camera (%d)\n", i);
                }
+               pdev->vopen = 0;
+               Trace(TRACE_OPEN, "<< video_close()\n");
+       } 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;
        }
-       pdev->vopen = 0;
-       Trace(TRACE_OPEN, "<< video_close()\n");
+       unlock_kernel();
+
        return 0;
 }
 
@@ -1989,20 +2006,21 @@ 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 */
-       Trace(TRACE_PROBE, "Unregistering video device in disconnect().\n");
-       video_unregister_device(pdev->vdev);
-
-       /* Free memory (don't set pdev to 0 just yet) */
-       kfree(pdev);
+       if(pdev->vopen) {
+               pdev->unplugged = 1;
+       } else {
+               /* Device is closed, so we can safely unregister it */
+               Trace(TRACE_PROBE, "Unregistering video device in disconnect().\n");
+               pwc_cleanup(pdev);
+               /* Free memory (don't set pdev to 0 just yet) */
+               kfree(pdev);
 
 disconnect_out:
-       /* 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;
+               /* 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();
 }

diff --git a/drivers/usb/media/pwc/pwc.h b/drivers/usb/media/pwc/pwc.h
index 6dd76bb3dff16ae4f95f53744df0b094c4e3670c..bb888e80514a46f8648e7462b110154f86f03451 100644 (file)
--- a/drivers/usb/media/pwc/pwc.h
+++ b/drivers/usb/media/pwc/pwc.h
@@ -149,6 +149,7 @@ 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];