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

BugLink: http://bugs.launchpad.net/bugs/890952

commit 0e6c7f746ea99089fb3263709075c20485a479ae upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

1 files changed, 12 insertions, 10 deletions

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 2d671af6b7e..104620b3764 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -114,18 +114,20 @@ 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);
 }