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Date: Tue, 10 Oct 2017 21:50:24 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Alan Stern <stern@...land.harvard.edu>,
Andrey Konovalov <andreyknvl@...gle.com>,
Felipe Balbi <felipe.balbi@...ux.intel.com>
Subject: [PATCH 3.18 03/32] USB: gadgetfs: fix copy_to_user while holding spinlock
3.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alan Stern <stern@...land.harvard.edu>
commit 6e76c01e71551cb221c1f3deacb9dcd9a7346784 upstream.
The gadgetfs driver as a long-outstanding FIXME, regarding a call of
copy_to_user() made while holding a spinlock. This patch fixes the
issue by dropping the spinlock and using the dev->udc_usage mechanism
introduced by another recent patch to guard against status changes
while the lock isn't held.
Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Acked-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
drivers/usb/gadget/legacy/inode.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1067,11 +1067,14 @@ ep0_read (struct file *fd, char __user *
retval = -EIO;
else {
len = min (len, (size_t)dev->req->actual);
-// FIXME don't call this with the spinlock held ...
+ ++dev->udc_usage;
+ spin_unlock_irq(&dev->lock);
if (copy_to_user (buf, dev->req->buf, len))
retval = -EFAULT;
else
retval = len;
+ spin_lock_irq(&dev->lock);
+ --dev->udc_usage;
clean_req (dev->gadget->ep0, dev->req);
/* NOTE userspace can't yet choose to stall */
}
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