usb: gadget: function: add spinlock for rndis response list

[Daehwan Jung <dh10.jung@xxxxxxxxxxx>]

There's no lock for rndis response list. It could cause list corruption
if two different list_add at the same time like below.
It's better to add in rndis_add_response / rndis_free_response
/ rndis_get_next_response to prevent any race condition on response list.

[  361.894299] [1:   irq/191-dwc3:16979] list_add corruption.
next->prev should be prev (ffffff80651764d0),
but was ffffff883dc36f80. (next=ffffff80651764d0).

[  361.904380] [1:   irq/191-dwc3:16979] Call trace:
[  361.904391] [1:   irq/191-dwc3:16979]  __list_add_valid+0x74/0x90
[  361.904401] [1:   irq/191-dwc3:16979]  rndis_msg_parser+0x168/0x8c0
[  361.904409] [1:   irq/191-dwc3:16979]  rndis_command_complete+0x24/0x84
[  361.904417] [1:   irq/191-dwc3:16979]  usb_gadget_giveback_request+0x20/0xe4
[  361.904426] [1:   irq/191-dwc3:16979]  dwc3_gadget_giveback+0x44/0x60
[  361.904434] [1:   irq/191-dwc3:16979]  dwc3_ep0_complete_data+0x1e8/0x3a0
[  361.904442] [1:   irq/191-dwc3:16979]  dwc3_ep0_interrupt+0x29c/0x3dc
[  361.904450] [1:   irq/191-dwc3:16979]  dwc3_process_event_entry+0x78/0x6cc
[  361.904457] [1:   irq/191-dwc3:16979]  dwc3_process_event_buf+0xa0/0x1ec
[  361.904465] [1:   irq/191-dwc3:16979]  dwc3_thread_interrupt+0x34/0x5c

Fixes: f6281af9d62e ("usb: gadget: rndis: use list_for_each_entry_safe")
Signed-off-by: Daehwan Jung <dh10.jung@xxxxxxxxxxx>
---
 drivers/usb/gadget/function/rndis.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/usb/gadget/function/rndis.c b/drivers/usb/gadget/function/rndis.c
index b7ccf1803656..b4d58324e2d2 100644
--- a/drivers/usb/gadget/function/rndis.c
+++ b/drivers/usb/gadget/function/rndis.c
@@ -1011,16 +1011,21 @@ void rndis_add_hdr(struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(rndis_add_hdr);
 
+/* add spinlock to prevent race condition for rndis response list */
+static DEFINE_SPINLOCK(resp_lock);
+
 void rndis_free_response(struct rndis_params *params, u8 *buf)
 {
 	rndis_resp_t *r, *n;
 
+	spin_lock(&resp_lock);
 	list_for_each_entry_safe(r, n, &params->resp_queue, list) {
 		if (r->buf == buf) {
 			list_del(&r->list);
 			kfree(r);
 		}
 	}
+	spin_unlock(&resp_lock);
 }
 EXPORT_SYMBOL_GPL(rndis_free_response);
 
@@ -1030,14 +1035,17 @@ u8 *rndis_get_next_response(struct rndis_params *params, u32 *length)
 
 	if (!length) return NULL;
 
+	spin_lock(&resp_lock);
 	list_for_each_entry_safe(r, n, &params->resp_queue, list) {
 		if (!r->send) {
 			r->send = 1;
 			*length = r->length;
+			spin_unlock(&resp_lock);
 			return r->buf;
 		}
 	}
 
+	spin_unlock(&resp_lock);
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(rndis_get_next_response);
@@ -1054,7 +1062,9 @@ static rndis_resp_t *rndis_add_response(struct rndis_params *params, u32 length)
 	r->length = length;
 	r->send = 0;
 
+	spin_lock(&resp_lock);
 	list_add_tail(&r->list, &params->resp_queue);
+	spin_unlock(&resp_lock);
 	return r;
 }
 
-- 
2.31.1