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Subject[019/264] xhci-mem.c: Check for ring->first_seg != NULL
3.1-stable review patch.  If anyone has any objections, please let me know.

------------------
From: Kautuk Consul <consul.kautuk@gmail.com>

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>

---
drivers/usb/host/xhci-mem.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
--- 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 *xhc
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);
}




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