3.2.97-rc1 review patch. If anyone has any objections, please let me know.
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From: Alan Stern stern@rowland.harvard.edu
commit 520b72fc64debf8a86c3853b8e486aa5982188f0 upstream.
The gadgetfs driver (drivers/usb/gadget/legacy/inode.c) was written before the UDC and composite frameworks were adopted; it is a legacy driver. As such, it expects that once bound to a UDC controller, it will not be unbound until it unregisters itself.
However, the UDC framework does unbind function drivers while they are still registered. When this happens, it can cause the gadgetfs driver to misbehave or crash. For example, userspace can cause a crash by opening the device file and doing an ioctl call before setting up a configuration (found by Andrey Konovalov using the syzkaller fuzzer).
This patch adds checks and synchronization to prevent these bad behaviors. It adds a udc_usage counter that the driver increments at times when it is using a gadget interface without holding the private spinlock. The unbind routine waits for this counter to go to 0 before returning, thereby ensuring that the UDC is no longer in use.
The patch also adds a check in the dev_ioctl() routine to make sure the driver is bound to a UDC before dereferencing the gadget pointer, and it makes destroy_ep_files() synchronize with the endpoint I/O routines, to prevent the user from accessing an endpoint data structure after it has been removed.
Signed-off-by: Alan Stern stern@rowland.harvard.edu Reported-by: Andrey Konovalov andreyknvl@google.com Tested-by: Andrey Konovalov andreyknvl@google.com Acked-by: Felipe Balbi felipe.balbi@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [bwh: Backported to 3.2: - Expand locked section in ep0_write() to match upstream - Adjust filename, context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/drivers/usb/gadget/inode.c +++ b/drivers/usb/gadget/inode.c @@ -24,7 +24,7 @@ #include <linux/sched.h> #include <linux/slab.h> #include <linux/poll.h> - +#include <linux/delay.h> #include <linux/device.h> #include <linux/moduleparam.h>
@@ -112,6 +112,7 @@ enum ep0_state { struct dev_data { spinlock_t lock; atomic_t count; + int udc_usage; enum ep0_state state; /* P: lock */ struct usb_gadgetfs_event event [N_EVENT]; unsigned ev_next; @@ -608,9 +609,9 @@ static void ep_aio_complete(struct usb_e priv->actual = req->actual; kick_iocb(iocb); } - spin_unlock(&epdata->dev->lock);
usb_ep_free_request(ep, req); + spin_unlock(&epdata->dev->lock); put_ep(epdata); }
@@ -1010,9 +1011,11 @@ ep0_read (struct file *fd, char __user * struct usb_request *req = dev->req;
if ((retval = setup_req (ep, req, 0)) == 0) { + ++dev->udc_usage; spin_unlock_irq (&dev->lock); retval = usb_ep_queue (ep, req, GFP_KERNEL); spin_lock_irq (&dev->lock); + --dev->udc_usage; } dev->state = STATE_DEV_CONNECTED;
@@ -1207,6 +1210,7 @@ ep0_write (struct file *fd, const char _ retval = setup_req (dev->gadget->ep0, dev->req, len); if (retval == 0) { dev->state = STATE_DEV_CONNECTED; + ++dev->udc_usage; spin_unlock_irq (&dev->lock); if (copy_from_user (dev->req->buf, buf, len)) retval = -EFAULT; @@ -1217,12 +1221,13 @@ ep0_write (struct file *fd, const char _ dev->gadget->ep0, dev->req, GFP_KERNEL); } + spin_lock_irq(&dev->lock); + --dev->udc_usage; if (retval < 0) { - spin_lock_irq (&dev->lock); clean_req (dev->gadget->ep0, dev->req); - spin_unlock_irq (&dev->lock); } else retval = len; + spin_unlock_irq(&dev->lock);
return retval; } @@ -1314,9 +1319,21 @@ static long dev_ioctl (struct file *fd, struct usb_gadget *gadget = dev->gadget; long ret = -ENOTTY;
- if (gadget->ops->ioctl) + spin_lock_irq(&dev->lock); + if (dev->state == STATE_DEV_OPENED || + dev->state == STATE_DEV_UNBOUND) { + /* Not bound to a UDC */ + } else if (gadget->ops->ioctl) { + ++dev->udc_usage; + spin_unlock_irq(&dev->lock); + ret = gadget->ops->ioctl (gadget, code, value);
+ spin_lock_irq(&dev->lock); + --dev->udc_usage; + } + spin_unlock_irq(&dev->lock); + return ret; }
@@ -1551,10 +1568,12 @@ delegate: if (value < 0) break;
+ ++dev->udc_usage; spin_unlock (&dev->lock); value = usb_ep_queue (gadget->ep0, dev->req, GFP_KERNEL); spin_lock (&dev->lock); + --dev->udc_usage; if (value < 0) { clean_req (gadget->ep0, dev->req); break; @@ -1578,8 +1597,12 @@ delegate: req->length = value; req->zero = value < w_length;
+ ++dev->udc_usage; spin_unlock (&dev->lock); value = usb_ep_queue (gadget->ep0, req, GFP_KERNEL); + spin_lock(&dev->lock); + --dev->udc_usage; + spin_unlock(&dev->lock); if (value < 0) { DBG (dev, "ep_queue --> %d\n", value); req->status = 0; @@ -1609,21 +1632,24 @@ restart: /* break link to FS */ ep = list_entry (entry, struct ep_data, epfiles); list_del_init (&ep->epfiles); + spin_unlock_irq (&dev->lock); + dentry = ep->dentry; ep->dentry = NULL; parent = dentry->d_parent->d_inode;
/* break link to controller */ + mutex_lock(&ep->lock); if (ep->state == STATE_EP_ENABLED) (void) usb_ep_disable (ep->ep); ep->state = STATE_EP_UNBOUND; usb_ep_free_request (ep->ep, ep->req); ep->ep = NULL; + mutex_unlock(&ep->lock); + wake_up (&ep->wait); put_ep (ep);
- spin_unlock_irq (&dev->lock); - /* break link to dcache */ mutex_lock (&parent->i_mutex); d_delete (dentry); @@ -1697,6 +1723,11 @@ gadgetfs_unbind (struct usb_gadget *gadg
spin_lock_irq (&dev->lock); dev->state = STATE_DEV_UNBOUND; + while (dev->udc_usage > 0) { + spin_unlock_irq(&dev->lock); + usleep_range(1000, 2000); + spin_lock_irq(&dev->lock); + } spin_unlock_irq (&dev->lock);
destroy_ep_files (dev);