Re: Missing skb_pad() return value checks in rt2x00 driver

[Seth Forshee <seth.forshee@canonical.com>]

On Mon, Feb 14, 2011 at 11:03:36AM +0100, Ivo Van Doorn wrote:
> Hi,
> 
> Well this patch managed to slip through my list. :S

No problem, glad it finally caught your attention :)

> > From 4a8b3969775cd233750a1b74b1d4f5fc065932bf Mon Sep 17 00:00:00 2001
> > From: Seth Forshee <seth.forshee@canonical.com>
> > Date: Mon, 7 Feb 2011 13:50:33 -0600
> > Subject: [PATCH] rt2x00: Check for errors from skb_pad() calls
> >
> > 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.
> 
> Thanks for the updated patch. I only have one small request.
> 
> > +       if (padding_len && skb_pad(entry->skb, padding_len)) {
> > +               dev_err(rt2x00dev->dev, "Failure padding beacon, aborting\n");
> 
> Please change to:
>   ERROR(rt2x00dev, "Failure padding beacon, aborting\n");
> same for the other changed drivers in this patch.

Done, updated patch follows.


>From 0de24c34fc6f59d1d557a3cb16adcc32414d4c46 Mon Sep 17 00:00:00 2001
From: Seth Forshee <seth.forshee@canonical.com>
Date: Mon, 14 Feb 2011 08:52:25 -0600
Subject: [PATCH] rt2x00: Check for errors from skb_pad() calls

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.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
 drivers/net/wireless/rt2x00/rt2800lib.c |   12 ++++++++++--
 drivers/net/wireless/rt2x00/rt61pci.c   |   12 ++++++++++--
 drivers/net/wireless/rt2x00/rt73usb.c   |   12 ++++++++++--
 3 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/rt2x00/rt2800lib.c b/drivers/net/wireless/rt2x00/rt2800lib.c
index c9bf074..7a68a67 100644
--- a/drivers/net/wireless/rt2x00/rt2800lib.c
+++ b/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);
diff --git a/drivers/net/wireless/rt2x00/rt61pci.c b/drivers/net/wireless/rt2x00/rt61pci.c
index dd2164d..927a4a3 100644
--- a/drivers/net/wireless/rt2x00/rt61pci.c
+++ b/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);
diff --git a/drivers/net/wireless/rt2x00/rt73usb.c b/drivers/net/wireless/rt2x00/rt73usb.c
index 5ff72de..6e9981a 100644
--- a/drivers/net/wireless/rt2x00/rt73usb.c
+++ b/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);
-- 
1.7.1