xhci-mem.c: Check for ring->first_seg != NULL

There are 2 situations wherein the xhci_ring* might not get freed:
- When xhci_ring_alloc() -> xhci_segment_alloc() returns NULL and
  we goto the fail: label in xhci_ring_alloc. In this case, the ring
  will not get kfreed.
- When the num_segs argument to xhci_ring_alloc is passed as 0 and
  we try to free the rung after that.
  ( This doesn't really happen as of now in the code but we seem to
    be entertaining num_segs=0 in xhci_ring_alloc )

This should be backported to kernels as old as 2.6.31.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 94a8b28d602e04cde6bfca58d1d09ab764ee538e..e4513ab015b40826b4b65d99268466e5ce0a0b59 100644 (file)
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -112,18 +112,20 @@ void xhci_ring_free(struct xhci_hcd *xhci, struct xhci_ring *ring)
        struct xhci_segment *seg;
        struct xhci_segment *first_seg;
 
-       if (!ring || !ring->first_seg)
+       if (!ring)
                return;
-       first_seg = ring->first_seg;
-       seg = first_seg->next;
-       xhci_dbg(xhci, "Freeing ring at %p\n", ring);
-       while (seg != first_seg) {
-               struct xhci_segment *next = seg->next;
-               xhci_segment_free(xhci, seg);
-               seg = next;
+       if (ring->first_seg) {
+               first_seg = ring->first_seg;
+               seg = first_seg->next;
+               xhci_dbg(xhci, "Freeing ring at %p\n", ring);
+               while (seg != first_seg) {
+                       struct xhci_segment *next = seg->next;
+                       xhci_segment_free(xhci, seg);
+                       seg = next;
+               }
+               xhci_segment_free(xhci, first_seg);
+               ring->first_seg = NULL;
        }
-       xhci_segment_free(xhci, first_seg);
-       ring->first_seg = NULL;
        kfree(ring);
 }