From e70c51ae7f8f5e1389cb51cbadc4a1d60f10f7fd Mon Sep 17 00:00:00 2001 From: AMAN DEEP Date: Tue, 21 Jul 2015 17:20:27 +0300 Subject: [PATCH] usb: xhci: Bugfix for NULL pointer deference in xhci_endpoint_init() function 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 Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-mem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c index 677f032482f7..31bed5f7d0eb 100644 --- a/drivers/usb/host/xhci-mem.c +++ b/drivers/usb/host/xhci-mem.c @@ -1400,10 +1400,10 @@ int xhci_endpoint_init(struct xhci_hcd *xhci, /* 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); } -- 2.20.1