On Wed, May 27, 2020 at 10:58 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> The problem is that we always copy a minimum of ETH_ZLEN (60) bytes from
> skb->data even when skb->len is less than ETH_ZLEN so it leads to a read
> overflow.
>
> The fix is to pad skb->data with zeroes so that it's never less than
> ETH_ZLEN bytes.
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Reported-by: Hu Jiahui <kirin.say@xxxxxxxxx>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> v2: remove an unnecessary if statement
> increment the ->tx_dropped count on failure
> fix found two more instances of the same bug.
> fix typo in the "Cc: <stable@xxxxxxxxxxxxxxx>" tag
>
> drivers/net/wireless/cisco/airo.c | 26 ++++++++++++++++----------
> 1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/wireless/cisco/airo.c b/drivers/net/wireless/cisco/airo.c
> index 8363f91df7ea..c80712e61ccf 100644
> --- a/drivers/net/wireless/cisco/airo.c
> +++ b/drivers/net/wireless/cisco/airo.c
> @@ -1925,6 +1925,11 @@ static netdev_tx_t mpi_start_xmit(struct sk_buff *skb,
> airo_print_err(dev->name, "%s: skb == NULL!",__func__);
> return NETDEV_TX_OK;
> }
> + if (skb_padto(skb, ETH_ZLEN)) {
> + dev->stats.tx_dropped++;
> + return NETDEV_TX_OK;
> + }
> +
> npacks = skb_queue_len (&ai->txq);
>
> if (npacks >= MAXTXQ - 1) {
> @@ -1975,8 +1980,7 @@ static int mpi_send_packet (struct net_device *dev)
> return 0;
> }
>
> - /* check min length*/
> - len = ETH_ZLEN < skb->len ? skb->len : ETH_ZLEN;
Note that skb_padto() does not change skb->len
So this patch could trigger a hardware bug.
> + len = skb->len;
> buffer = skb->data;
>
> ai->txfids[0].tx_desc.offset = 0;
> @@ -2118,7 +2122,6 @@ static void airo_end_xmit(struct net_device *dev) {
> static netdev_tx_t airo_start_xmit(struct sk_buff *skb,
> struct net_device *dev)
> {
> - s16 len;
> int i, j;
> struct airo_info *priv = dev->ml_priv;
> u32 *fids = priv->fids;
> @@ -2127,6 +2130,10 @@ static netdev_tx_t airo_start_xmit(struct sk_buff *skb,
> airo_print_err(dev->name, "%s: skb == NULL!", __func__);
> return NETDEV_TX_OK;
> }
> + if (skb_padto(skb, ETH_ZLEN)) {
> + dev->stats.tx_dropped++;
> + return NETDEV_TX_OK;
> + }
>
> /* Find a vacant FID */
> for( i = 0; i < MAX_FIDS / 2 && (fids[i] & 0xffff0000); i++ );
> @@ -2140,10 +2147,8 @@ static netdev_tx_t airo_start_xmit(struct sk_buff *skb,
> return NETDEV_TX_BUSY;
> }
> }
> - /* check min length*/
> - len = ETH_ZLEN < skb->len ? skb->len : ETH_ZLEN;
> /* Mark fid as used & save length for later */
> - fids[i] |= (len << 16);
> + fids[i] |= (skb->len << 16);
> priv->xmit.skb = skb;
> priv->xmit.fid = i;
> if (down_trylock(&priv->sem) != 0) {
> @@ -2185,7 +2190,6 @@ static void airo_end_xmit11(struct net_device *dev) {
> static netdev_tx_t airo_start_xmit11(struct sk_buff *skb,
> struct net_device *dev)
> {
> - s16 len;
> int i, j;
> struct airo_info *priv = dev->ml_priv;
> u32 *fids = priv->fids;
> @@ -2201,6 +2205,10 @@ static netdev_tx_t airo_start_xmit11(struct sk_buff *skb,
> airo_print_err(dev->name, "%s: skb == NULL!", __func__);
> return NETDEV_TX_OK;
> }
> + if (skb_padto(skb, ETH_ZLEN)) {
> + dev->stats.tx_dropped++;
> + return NETDEV_TX_OK;
> + }
>
> /* Find a vacant FID */
> for( i = MAX_FIDS / 2; i < MAX_FIDS && (fids[i] & 0xffff0000); i++ );
> @@ -2214,10 +2222,8 @@ static netdev_tx_t airo_start_xmit11(struct sk_buff *skb,
> return NETDEV_TX_BUSY;
> }
> }
> - /* check min length*/
> - len = ETH_ZLEN < skb->len ? skb->len : ETH_ZLEN;
> /* Mark fid as used & save length for later */
> - fids[i] |= (len << 16);
> + fids[i] |= (skb->len << 16);
> priv->xmit11.skb = skb;
> priv->xmit11.fid = i;
> if (down_trylock(&priv->sem) != 0) {
> --
> 2.11.0
>
