rsi: fix memory alignment issue in ARM32 platforms

During testing in ARM32 platforms, observed below kernel panic, as driver
accessing data beyond the allocated memory while submitting URB to USB.

Fix: Resolved this by specifying correct length by considering 64 bit
alignment. so that, USB bus driver will access only allocated memory.

Unit-test: Tested and confirm that driver bring up and scanning,
connection and data transfer works fine with this fix.

...skipping...
[   25.389450] Unable to handle kernel paging request at virtual
	       address 5aa11422
[   25.403078] Internal error: Oops: 5 [#1] SMP ARM
[   25.407703] Modules linked in: rsi_usb
[   25.411473] CPU: 1 PID: 317 Comm: RX-Thread Not tainted 4.18.0-rc7 #1
[   25.419221] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
[   25.425764] PC is at skb_release_data+0x90/0x168
[   25.430393] LR is at skb_release_all+0x28/0x2c
[   25.434842] pc : [<807435b0>] lr : [<80742ba0>] psr: 200e0013 5aa1141e
[   25.464633] Flags: nzCv  IRQs on  FIQs on  Mode SVC_32 ISA ARM Segment none
[   25.477524] Process RX-Thread (pid: 317, stack limit = 0x(ptrval))
[   25.483709] Stack: (0xedf69ed8 to 0xedf6a000)
[   25.569907] Backtrace:
[   25.572368] [<80743520>] (skb_release_data) from [<80742ba0>]
	       (skb_release_all+0x28/0x2c)
[   25.580555] r9:7f00258c r8:00000001 r7:ee355000 r6:eddab0d0
	       r5:eddab000 r4:eddbb840
[   25.588308] [<80742b78>] (skb_release_all) from [<807432cc>]
	       (consume_skb+0x30/0x50)
[   25.596055] r5:eddab000 r4:eddbb840
[   25.599648] [<8074329c>] (consume_skb) from [<7f00117c>]
	       (rsi_usb_rx_thread+0x64/0x12c [rsi_usb])
[   25.608524] r5:eddab000 r4:eddbb840
[   25.612116] [<7f001118>] (rsi_usb_rx_thread [rsi_usb]) from
	       [<80142750>] (kthread+0x11c/0x15c)
[   25.620735] r10:ee9ff9e0 r9:edcde3b8 r8:ee355000 r7:edf68000
	       r6:edd3a780 r5:00000000
[   25.628567] r4:edcde380
[   25.631110] [<80142634>] (kthread) from [<801010e8>]
	       (ret_from_fork+0x14/0x2c)
[   25.638336] Exception stack(0xedf69fb0 to 0xedf69ff8)
[   25.682929] ---[ end trace 8236a5496f5b5d3b ]---
Signed-off-by: Siva Rebbagondla <siva.rebbagondla@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/rsi/rsi_91x_usb.c

@@ -266,15 +266,17 @@ static void rsi_rx_done_handler(struct urb *urb)
 	if (urb->status)
 		goto out;
 
-	if (urb->actual_length <= 0) {
-		rsi_dbg(INFO_ZONE, "%s: Zero length packet\n", __func__);
+	if (urb->actual_length <= 0 ||
+	    urb->actual_length > rx_cb->rx_skb->len) {
+		rsi_dbg(INFO_ZONE, "%s: Invalid packet length = %d\n",
+			__func__, urb->actual_length);
 		goto out;
 	}
 	if (skb_queue_len(&dev->rx_q) >= RSI_MAX_RX_PKTS) {
 		rsi_dbg(INFO_ZONE, "Max RX packets reached\n");
 		goto out;
 	}
-	skb_put(rx_cb->rx_skb, urb->actual_length);
+	skb_trim(rx_cb->rx_skb, urb->actual_length);
 	skb_queue_tail(&dev->rx_q, rx_cb->rx_skb);
 
 	rsi_set_event(&dev->rx_thread.event);
@@ -308,6 +310,7 @@ static int rsi_rx_urb_submit(struct rsi_hw *adapter, u8 ep_num)
 	if (!skb)
 		return -ENOMEM;
 	skb_reserve(skb, MAX_DWORD_ALIGN_BYTES);
+	skb_put(skb, RSI_MAX_RX_USB_PKT_SIZE - MAX_DWORD_ALIGN_BYTES);
 	dword_align_bytes = (unsigned long)skb->data & 0x3f;
 	if (dword_align_bytes > 0)
 		skb_push(skb, dword_align_bytes);
@@ -319,7 +322,7 @@ static int rsi_rx_urb_submit(struct rsi_hw *adapter, u8 ep_num)
 			  usb_rcvbulkpipe(dev->usbdev,
 			  dev->bulkin_endpoint_addr[ep_num - 1]),
 			  urb->transfer_buffer,
-			  RSI_MAX_RX_USB_PKT_SIZE,
+			  skb->len,
 			  rsi_rx_done_handler,
 			  rx_cb);