[PATCH 3/3] rt2x00: Check for errors from skb_pad() calls

[Seth Forshee]

BugLink: http://bugs.launchpad.net/bugs/659143

Commit 739fd94 ("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.

(backported from d76dfc612b40b6a9de0a3fe57fe1fa3db7a1ae3b wireless-next-2.6)
Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
Acked-by: Ivo van Doorn <IvDoorn at gmail.com>
Signed-off-by: John W. Linville <linville at tuxdriver.com>
---
 drivers/net/wireless/rt2x00/rt2800pci.c |   11 +++++++++--
 drivers/net/wireless/rt2x00/rt61pci.c   |   11 +++++++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/rt2x00/rt2800pci.c b/drivers/net/wireless/rt2x00/rt2800pci.c
index 9ad676d..e13666e 100644
--- a/drivers/net/wireless/rt2x00/rt2800pci.c
+++ b/drivers/net/wireless/rt2x00/rt2800pci.c
@@ -690,13 +690,14 @@ static void rt2800pci_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.
 	 */
 	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);
 
@@ -710,7 +711,13 @@ static void rt2800pci_write_beacon(struct queue_entry *entry,
 	 * 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);
diff --git a/drivers/net/wireless/rt2x00/rt61pci.c b/drivers/net/wireless/rt2x00/rt61pci.c
index 23bcb65..f4d1ec9 100644
--- a/drivers/net/wireless/rt2x00/rt61pci.c
+++ b/drivers/net/wireless/rt2x00/rt61pci.c
@@ -1864,13 +1864,14 @@ 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);
 
@@ -1878,7 +1879,13 @@ 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);
-- 
1.7.1