[35/83] xhci: fix list access before init

[Ben Hutchings]

3.2.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vladimir Murzin <murzin.v@xxxxxxxxx>

commit 88696ae432ce7321540ac53d9caab3de9118b094 upstream.

If for whatever reason we fall into fail path in xhci_mem_init()
before bw table gets initialized we may access the uninitialized lists
in xhci_mem_cleanup().

Check for bw table before traversing lists in cleanup routine.

This patch should be backported to kernels as old as 3.2, that contain
the commit 839c817ce67178ca3c7c7ad534c571bba1e69ebe "xhci: Store
information about roothubs and TTs."

Reported-by: Sergey Dyasly <dserrg@xxxxxxxxx>
Tested-by: Sergey Dyasly <dserrg@xxxxxxxxx>
Signed-off-by: Vladimir Murzin <murzin.v@xxxxxxxxx>
Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/host/xhci-mem.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1755,6 +1755,9 @@ void xhci_mem_cleanup(struct xhci_hcd *x
 	}
 	spin_unlock_irqrestore(&xhci->lock, flags);
 
+	if (!xhci->rh_bw)
+		goto no_bw;
+
 	num_ports = HCS_MAX_PORTS(xhci->hcs_params1);
 	for (i = 0; i < num_ports; i++) {
 		struct xhci_interval_bw_table *bwt = &xhci->rh_bw[i].bw_table;
@@ -1773,6 +1776,7 @@ void xhci_mem_cleanup(struct xhci_hcd *x
 		}
 	}
 
+no_bw:
 	xhci->num_usb2_ports = 0;
 	xhci->num_usb3_ports = 0;
 	xhci->num_active_eps = 0;

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