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NET: Fix possible corruption in bpqether driver

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The bpq ether driver is modifying the data art of the skb by first
dropping the KISS byte (a command byte for the radio) then prepending the
length + 4 of the remaining AX.25 packet to be transmitted as a little
endian 16-bit number.  If the high byte of the length has a different
value than the dropped KISS byte users of clones of the skb may observe
this as corruption.  This was observed with by running listen(8) -a which
uses a packet socket which clones transmit packets.  The corruption will
then typically be displayed for as a KISS "TX Delay" command for AX.25
packets in the range of 252..508 bytes or any other KISS command for
yet larger packets.

Fixed by using skb_cow to create a private copy should the skb be cloned.
Using skb_cow also allows us to cleanup the old logic to ensure sufficient
headroom in the skb.

While at it, replace a return of 0 from bpq_xmit with the proper constant
NETDEV_TX_OK which is now being used everywhere else in this function.

Affected: all 2.2, 2.4 and 2.6 kernels.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Reported-by: Jann Traschewski <jann@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ralf Baechle 2009-09-02 23:09:29 -07:00 committed by David S. Miller
parent ab08999d60
commit 3eb0027594
1 changed files with 10 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
drivers/net/hamradio/bpqether.c
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@ -249,7 +249,6 @@ drop:
*/
static netdev_tx_t bpq_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct sk_buff *newskb;
unsigned char *ptr;
struct bpqdev *bpq;
int size;
@ -263,28 +262,23 @@ static netdev_tx_t bpq_xmit(struct sk_buff *skb, struct net_device *dev)
return NETDEV_TX_OK;
}
skb_pull(skb, 1);
skb_pull(skb, 1); /* Drop KISS byte */
size = skb->len;
/*
* The AX.25 code leaves enough room for the ethernet header, but
* sendto() does not.
* We're about to mess with the skb which may still shared with the
* generic networking code so unshare and ensure it's got enough
* space for the BPQ headers.
*/
if (skb_headroom(skb) < AX25_BPQ_HEADER_LEN) { /* Ough! */
if ((newskb = skb_realloc_headroom(skb, AX25_BPQ_HEADER_LEN)) == NULL) {
printk(KERN_WARNING "bpqether: out of memory\n");
kfree_skb(skb);
return NETDEV_TX_OK;
}
if (skb->sk != NULL)
skb_set_owner_w(newskb, skb->sk);
if (skb_cow(skb, AX25_BPQ_HEADER_LEN)) {
if (net_ratelimit())
pr_err("bpqether: out of memory\n");
kfree_skb(skb);
skb = newskb;
return NETDEV_TX_OK;
}
ptr = skb_push(skb, 2);
ptr = skb_push(skb, 2); /* Make space for length */
*ptr++ = (size + 5) % 256;
*ptr++ = (size + 5) / 256;