Patch "usb: xhci: Bugfix for NULL pointer deference in xhci_endpoint_init() function" has been added to the 4.1-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    usb: xhci: Bugfix for NULL pointer deference in xhci_endpoint_init() function

to the 4.1-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-xhci-bugfix-for-null-pointer-deference-in-xhci_endpoint_init-function.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 3496810663922617d4b706ef2780c279252ddd6a Mon Sep 17 00:00:00 2001
From: AMAN DEEP <aman.deep@samsung.com>
Date: Tue, 21 Jul 2015 17:20:27 +0300
Subject: usb: xhci: Bugfix for NULL pointer deference in xhci_endpoint_init() function

From: AMAN DEEP <aman.deep@samsung.com>

commit 3496810663922617d4b706ef2780c279252ddd6a upstream.

virt_dev->num_cached_rings counts on freed ring and is not updated
correctly. In xhci_free_or_cache_endpoint_ring() function, the free ring
is added into cache and then num_rings_cache is incremented as below:
		virt_dev->ring_cache[rings_cached] =
			virt_dev->eps[ep_index].ring;
		virt_dev->num_rings_cached++;
here, free ring pointer is added to a current index and then
index is incremented.
So current index always points to empty location in the ring cache.
For getting available free ring, current index should be decremented
first and then corresponding ring buffer value should be taken from ring
cache.

But In function xhci_endpoint_init(), the num_rings_cached index is
accessed before decrement.
		virt_dev->eps[ep_index].new_ring =
			virt_dev->ring_cache[virt_dev->num_rings_cached];
		virt_dev->ring_cache[virt_dev->num_rings_cached] = NULL;
		virt_dev->num_rings_cached--;
This is bug in manipulating the index of ring cache.
And it should be as below:
		virt_dev->num_rings_cached--;
		virt_dev->eps[ep_index].new_ring =
			virt_dev->ring_cache[virt_dev->num_rings_cached];
		virt_dev->ring_cache[virt_dev->num_rings_cached] = NULL;

Signed-off-by: Aman Deep <aman.deep@samsung.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/host/xhci-mem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1427,10 +1427,10 @@ int xhci_endpoint_init(struct xhci_hcd *
 		/* Attempt to use the ring cache */
 		if (virt_dev->num_rings_cached == 0)
 			return -ENOMEM;
+		virt_dev->num_rings_cached--;
 		virt_dev->eps[ep_index].new_ring =
 			virt_dev->ring_cache[virt_dev->num_rings_cached];
 		virt_dev->ring_cache[virt_dev->num_rings_cached] = NULL;
-		virt_dev->num_rings_cached--;
 		xhci_reinit_cached_ring(xhci, virt_dev->eps[ep_index].new_ring,
 					1, type);
 	}


Patches currently in stable-queue which might be from aman.deep@samsung.com are

queue-4.1/usb-xhci-bugfix-for-null-pointer-deference-in-xhci_endpoint_init-function.patch