This is a note to let you know that I've just added the patch titled
USB: gadgetfs: Fix crash caused by inadequate synchronization
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-gadgetfs-fix-crash-caused-by-inadequate-synchronization.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 520b72fc64debf8a86c3853b8e486aa5982188f0 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 21 Sep 2017 13:23:58 -0400
Subject: USB: gadgetfs: Fix crash caused by inadequate synchronization
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Acked-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/gadget/legacy/inode.c | 41 +++++++++++++++++++++++++++++++++-----
1 file changed, 36 insertions(+), 5 deletions(-)
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -27,7 +27,7 @@
#include <linux/mmu_context.h>
#include <linux/aio.h>
#include <linux/uio.h>
-
+#include <linux/delay.h>
#include <linux/device.h>
#include <linux/moduleparam.h>
@@ -116,6 +116,7 @@ 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;
@@ -513,9 +514,9 @@ static void ep_aio_complete(struct usb_e
INIT_WORK(&priv->work, ep_user_copy_worker);
schedule_work(&priv->work);
}
- spin_unlock(&epdata->dev->lock);
usb_ep_free_request(ep, req);
+ spin_unlock(&epdata->dev->lock);
put_ep(epdata);
}
@@ -939,9 +940,11 @@ 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;
@@ -1131,6 +1134,7 @@ 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;
@@ -1142,6 +1146,7 @@ ep0_write (struct file *fd, const char _
GFP_KERNEL);
}
spin_lock_irq(&dev->lock);
+ --dev->udc_usage;
if (retval < 0) {
clean_req (dev->gadget->ep0, dev->req);
} else
@@ -1243,9 +1248,21 @@ 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;
}
@@ -1463,10 +1480,12 @@ 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;
@@ -1490,8 +1509,12 @@ 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;
@@ -1518,21 +1541,24 @@ static void destroy_ep_files (struct dev
/* break link to FS */
ep = list_first_entry (&dev->epfiles, struct ep_data, epfiles);
list_del_init (&ep->epfiles);
+ spin_unlock_irq (&dev->lock);
+
dentry = ep->dentry;
ep->dentry = NULL;
parent = d_inode(dentry->d_parent);
/* 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 */
inode_lock(parent);
d_delete (dentry);
@@ -1603,6 +1629,11 @@ 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);
Patches currently in stable-queue which might be from stern@xxxxxxxxxxxxxxxxxxx are
queue-4.9/usb-gadgetfs-fix-crash-caused-by-inadequate-synchronization.patch