Function dev_alloc_skb() may return a NULL pointer, thus its return value shall be checked against NULL before used. But in function ipw_packet_received_skb(), the return value of dev_alloc_skb()(called at drivers/tty/ipwireless/network.c:349) is not checked. So an invalid memory access fault may be triggered when the return value (held by variable skb) of dev_alloc_skb() is used as a parameter of function skb_reserve() at line 350.
The related code snippets are as following.
ipw_packet_received_skb @@drivers/tty/ipwireless/network.c:349
349        skb = dev_alloc_skb(length + 4);
350        skb_reserve(skb, 2);
351        memcpy(skb_put(skb, length), data, length);

Generally, the return value of dev_alloc_skb() is checked against NULL before it is used. Take fwnet_pd_new(), a function in file drivers/firewire/net.c, for example.
fwnet_pd_new @@ drivers/firewire/net.c:400
400        new->skb = dev_alloc_skb(dg_size + net->hard_header_len + 15);
401        if (new->skb == NULL)
402                goto fail_w_fi;
403
404        skb_reserve(new->skb, (net->hard_header_len + 15) & ~15);
405        new->pbuf = skb_put(new->skb, dg_size);
406        memcpy(new->pbuf + frag_off, frag_buf, frag_len);

Thanks

RUC_Soft_Sec