rt2x00: Check for errors from skb_pad() calls

Commit 739fd940 ("rt2x00: Pad beacon to multiple of 32 bits")
added calls to skb_pad() without checking the return value,
which could cause problems if any of those calls does happen
to fail. Add checks to prevent this from happening.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -773,13 +773,14 @@ void rt2800_write_beacon(struct queue_entry *entry, struct txentry_desc *txdesc)
 	struct skb_frame_desc *skbdesc = get_skb_frame_desc(entry->skb);
 	unsigned int beacon_base;
 	unsigned int padding_len;
-	u32 reg;
+	u32 orig_reg, reg;
 
 	/*
 	 * Disable beaconing while we are reloading the beacon data,
 	 * otherwise we might be sending out invalid data.
 	 */
 	rt2800_register_read(rt2x00dev, BCN_TIME_CFG, &reg);
+	orig_reg = reg;
 	rt2x00_set_field32(&reg, BCN_TIME_CFG_BEACON_GEN, 0);
 	rt2800_register_write(rt2x00dev, BCN_TIME_CFG, reg);
 
@@ -810,7 +811,14 @@ void rt2800_write_beacon(struct queue_entry *entry, struct txentry_desc *txdesc)
 	 * Write entire beacon with TXWI and padding to register.
 	 */
 	padding_len = roundup(entry->skb->len, 4) - entry->skb->len;
-	skb_pad(entry->skb, padding_len);
+	if (padding_len && skb_pad(entry->skb, padding_len)) {
+		ERROR(rt2x00dev, "Failure padding beacon, aborting\n");
+		/* skb freed by skb_pad() on failure */
+		entry->skb = NULL;
+		rt2800_register_write(rt2x00dev, BCN_TIME_CFG, orig_reg);
+		return;
+	}
+
 	beacon_base = HW_BEACON_OFFSET(entry->entry_idx);
 	rt2800_register_multiwrite(rt2x00dev, beacon_base, entry->skb->data,
 				   entry->skb->len + padding_len);

drivers/net/wireless/rt2x00/rt61pci.c

@@ -1978,13 +1978,14 @@ static void rt61pci_write_beacon(struct queue_entry *entry,
 	struct queue_entry_priv_pci *entry_priv = entry->priv_data;
 	unsigned int beacon_base;
 	unsigned int padding_len;
-	u32 reg;
+	u32 orig_reg, reg;
 
 	/*
 	 * Disable beaconing while we are reloading the beacon data,
 	 * otherwise we might be sending out invalid data.
 	 */
 	rt2x00pci_register_read(rt2x00dev, TXRX_CSR9, &reg);
+	orig_reg = reg;
 	rt2x00_set_field32(&reg, TXRX_CSR9_BEACON_GEN, 0);
 	rt2x00pci_register_write(rt2x00dev, TXRX_CSR9, reg);
 
@@ -2002,7 +2003,14 @@ static void rt61pci_write_beacon(struct queue_entry *entry,
 	 * Write entire beacon with descriptor and padding to register.
 	 */
 	padding_len = roundup(entry->skb->len, 4) - entry->skb->len;
-	skb_pad(entry->skb, padding_len);
+	if (padding_len && skb_pad(entry->skb, padding_len)) {
+		ERROR(rt2x00dev, "Failure padding beacon, aborting\n");
+		/* skb freed by skb_pad() on failure */
+		entry->skb = NULL;
+		rt2x00pci_register_write(rt2x00dev, TXRX_CSR9, orig_reg);
+		return;
+	}
+
 	beacon_base = HW_BEACON_OFFSET(entry->entry_idx);
 	rt2x00pci_register_multiwrite(rt2x00dev, beacon_base,
 				      entry_priv->desc, TXINFO_SIZE);

drivers/net/wireless/rt2x00/rt73usb.c

@@ -1533,13 +1533,14 @@ static void rt73usb_write_beacon(struct queue_entry *entry,
 	struct rt2x00_dev *rt2x00dev = entry->queue->rt2x00dev;
 	unsigned int beacon_base;
 	unsigned int padding_len;
-	u32 reg;
+	u32 orig_reg, reg;
 
 	/*
 	 * Disable beaconing while we are reloading the beacon data,
 	 * otherwise we might be sending out invalid data.
 	 */
 	rt2x00usb_register_read(rt2x00dev, TXRX_CSR9, &reg);
+	orig_reg = reg;
 	rt2x00_set_field32(&reg, TXRX_CSR9_BEACON_GEN, 0);
 	rt2x00usb_register_write(rt2x00dev, TXRX_CSR9, reg);
 
@@ -1563,7 +1564,14 @@ static void rt73usb_write_beacon(struct queue_entry *entry,
 	 * Write entire beacon with descriptor and padding to register.
 	 */
 	padding_len = roundup(entry->skb->len, 4) - entry->skb->len;
-	skb_pad(entry->skb, padding_len);
+	if (padding_len && skb_pad(entry->skb, padding_len)) {
+		ERROR(rt2x00dev, "Failure padding beacon, aborting\n");
+		/* skb freed by skb_pad() on failure */
+		entry->skb = NULL;
+		rt2x00usb_register_write(rt2x00dev, TXRX_CSR9, orig_reg);
+		return;
+	}
+
 	beacon_base = HW_BEACON_OFFSET(entry->entry_idx);
 	rt2x00usb_register_multiwrite(rt2x00dev, beacon_base, entry->skb->data,
 				      entry->skb->len + padding_len);