Commit 65b01bd5 authored Sep 20, 2011 by James Hogan Committed by Jiri Kosina Sep 20, 2011

HID: hidraw: protect hidraw_disconnect() better

The function hidraw_disconnect() only acquires the hidraw minors_lock
when clearing the entry in hidraw_table. However the device_destroy()
call can cause a userland read/write to return with an error. It may
cause the program to release the file descripter before the disconnect
is finished. hidraw_disconnect() has already set hidraw->exist to 0,
which makes hidraw_release() kfree the hidraw structure, which
hidraw_disconnect() continues to access and even tries to kfree again.
Similarly if a hidraw_release() occurs after setting hidraw->exist to 0,
the same thing can happen.

This is fixed by expanding the mutex critical section to cover the whole
function from setting hidraw->exist to 0 to freeing the hidraw
structure, preventing a hidraw_release() from interfering.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Tested-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

parent e4e436e0

drivers/hid/hidraw.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -510,13 +510,12 @@ void hidraw_disconnect(struct hid_device *hid)
		{
		struct hidraw *hidraw = hid->hidraw;

		mutex_lock(&minors_lock);
		hidraw->exist = 0;

		device_destroy(hidraw_class, MKDEV(hidraw_major, hidraw->minor));

		mutex_lock(&minors_lock);
		hidraw_table[hidraw->minor] = NULL;
		mutex_unlock(&minors_lock);

		if (hidraw->open) {
		hid_hw_close(hid);
		@@ -524,6 +523,7 @@ void hidraw_disconnect(struct hid_device *hid)
		} else {
		kfree(hidraw);
		}
		mutex_unlock(&minors_lock);
		}
		EXPORT_SYMBOL_GPL(hidraw_disconnect);

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