caif-shm: Bugfixes for caif_shmcore.c

Various bugfixes for caif_shmcore.c:
- fix deadlocks due to improper usage of spin-lock
- add missing spin-lock init
- don't call dev_kfree_skb() with irqs disabled,
use dev_kfree_skb_irq() instead.
- fix potential skb null pointer de-reference.

Squashed original patches from:
Rabin Vincent <[e-mail]>
Durga Prasada Rao BATHINA <[e-mail]>
Arun Murthy <[e-mail]>
Bibek Basu <[e-mail]>

Signed-off-by: Sjur Brændeland <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/caif/caif_shmcore.c

···
 		if ((avail_emptybuff > HIGH_WATERMARK) &&
 					(!pshm_drv->tx_empty_available)) {
 			pshm_drv->tx_empty_available = 1;
+			spin_unlock_irqrestore(&pshm_drv->lock, flags);
 			pshm_drv->cfdev.flowctrl
 					(pshm_drv->pshm_dev->pshm_netdev,
 								CAIF_FLOW_ON);
 
-			spin_unlock_irqrestore(&pshm_drv->lock, flags);
 
 			/* Schedule the work queue. if required */
 			if (!work_pending(&pshm_drv->shm_tx_work))
···
 			list_entry(pshm_drv->rx_full_list.next, struct buf_list,
 					list);
 		list_del_init(&pbuf->list);
+		spin_unlock_irqrestore(&pshm_drv->lock, flags);
 
 		/* Retrieve pointer to start of the packet descriptor area. */
 		pck_desc = (struct shm_pck_desc *) pbuf->desc_vptr;
···
 			pck_desc++;
 		}
 
+		spin_lock_irqsave(&pshm_drv->lock, flags);
 		list_add_tail(&pbuf->list, &pshm_drv->rx_pend_list);
 
 		spin_unlock_irqrestore(&pshm_drv->lock, flags);
···
 
 		if (skb == NULL)
 			goto send_msg;
-
 		/* Check the available no. of buffers in the empty list */
 		list_for_each(pos, &pshm_drv->tx_empty_list)
 			avail_emptybuff++;
···
 					pshm_drv->tx_empty_available) {
 			/* Update blocking condition. */
 			pshm_drv->tx_empty_available = 0;
+			spin_unlock_irqrestore(&pshm_drv->lock, flags);
 			pshm_drv->cfdev.flowctrl
 					(pshm_drv->pshm_dev->pshm_netdev,
 					CAIF_FLOW_OFF);
+			spin_lock_irqsave(&pshm_drv->lock, flags);
 		}
 		/*
 		 * We simply return back to the caller if we do not have space
···
 			}
 
 			skb = skb_dequeue(&pshm_drv->sk_qhead);
+			if (skb == NULL)
+				break;
 			/* Copy in CAIF frame. */
 			skb_copy_bits(skb, 0, pbuf->desc_vptr +
 					pbuf->frm_ofs + SHM_HDR_LEN +
···
 			pshm_drv->pshm_dev->pshm_netdev->stats.tx_packets++;
 			pshm_drv->pshm_dev->pshm_netdev->stats.tx_bytes +=
 									frmlen;
-			dev_kfree_skb(skb);
+			dev_kfree_skb_irq(skb);
 
 			/* Fill in the shared memory packet descriptor area. */
 			pck_desc = (struct shm_pck_desc *) (pbuf->desc_vptr);
···
 static int shm_netdev_tx(struct sk_buff *skb, struct net_device *shm_netdev)
 {
 	struct shmdrv_layer *pshm_drv;
-	unsigned long flags = 0;
 
 	pshm_drv = netdev_priv(shm_netdev);
 
-	spin_lock_irqsave(&pshm_drv->lock, flags);
-
 	skb_queue_tail(&pshm_drv->sk_qhead, skb);
-
-	spin_unlock_irqrestore(&pshm_drv->lock, flags);
 
 	/* Schedule Tx work queue. for deferred processing of skbs*/
 	if (!work_pending(&pshm_drv->shm_tx_work))
···
 		pshm_drv->shm_rx_addr = pshm_dev->shm_base_addr +
 						(NR_TX_BUF * TX_BUF_SZ);
 
+	spin_lock_init(&pshm_drv->lock);
 	INIT_LIST_HEAD(&pshm_drv->tx_empty_list);
 	INIT_LIST_HEAD(&pshm_drv->tx_pend_list);
 	INIT_LIST_HEAD(&pshm_drv->tx_full_list);
···
 		tx_buf->frm_ofs = SHM_CAIF_FRM_OFS;
 
 		if (pshm_dev->shm_loopback)
-			tx_buf->desc_vptr = (char *)tx_buf->phy_addr;
+			tx_buf->desc_vptr = (unsigned char *)tx_buf->phy_addr;
 		else
 			tx_buf->desc_vptr =
 					ioremap(tx_buf->phy_addr, TX_BUF_SZ);
···
 		rx_buf->len = RX_BUF_SZ;
 
 		if (pshm_dev->shm_loopback)
-			rx_buf->desc_vptr = (char *)rx_buf->phy_addr;
+			rx_buf->desc_vptr = (unsigned char *)rx_buf->phy_addr;
 		else
 			rx_buf->desc_vptr =
 					ioremap(rx_buf->phy_addr, RX_BUF_SZ);