[PATCH v2] xhci: solve a double free problem while doing s4

["Zhangjiantao (Kirin, nanjing)" <water.zhangjiantao@huawei.com>]

when system is doing s4, the process of xhci_resume may be as below:
1、xhci_mem_cleanup
2、xhci_init->xhci_mem_init->xhci_mem_cleanup(when memory is not enough).
xhci_mem_cleanup will be executed twice when system is out of memory.
xhci->port_caps is freed in xhci_mem_cleanup,but it isn't set to NULL.
It will be freed twice when xhci_mem_cleanup is called the second time.

We got following bug when system resumes from s4:

kernel BUG at mm/slub.c:309!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
CPU: 0 PID: 5929 Tainted: G S   W   5.4.96-arm64-desktop #1
pc : __slab_free+0x5c/0x424
lr : kfree+0x30c/0x32c

Call trace:
 __slab_free+0x5c/0x424
 kfree+0x30c/0x32c
 xhci_mem_cleanup+0x394/0x3cc
 xhci_mem_init+0x9ac/0x1070
 xhci_init+0x8c/0x1d0
 xhci_resume+0x1cc/0x5fc
 xhci_plat_resume+0x64/0x70
 platform_pm_thaw+0x28/0x60
 dpm_run_callback+0x54/0x24c
 device_resume+0xd0/0x200
 async_resume+0x24/0x60
 async_run_entry_fn+0x44/0x110
 process_one_work+0x1f0/0x490
 worker_thread+0x5c/0x450
 kthread+0x158/0x160
 ret_from_fork+0x10/0x24

Signed-off-by: Jiantao Zhang <water.zhangjiantao@huawei.com>
Signed-off-by: Tao Xue <xuetao09@huawei.com>
---
 drivers/usb/host/xhci-mem.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c index f66815f..e4b0c04 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1924,6 +1924,7 @@ void xhci_mem_cleanup(struct xhci_hcd *xhci)
 	xhci->hw_ports = NULL;
 	xhci->rh_bw = NULL;
 	xhci->ext_caps = NULL;
+	xhci->port_caps = NULL;
 
 	xhci->page_size = 0;
 	xhci->page_shift = 0;
--
2.7.4