[PATCH RFC net] ps3/gelic: Fix possible NULL pointer dereference

[Dan Carpenter]

This driver is PPC so I have never looked at the code before.  I noticed
another issue that was introduced last December in commit 3ce4f9c3fbb3
("net/ps3_gelic_net: Add gelic_descr structures").

net/ethernet/toshiba/ps3_gelic_net.c
   375  static int gelic_descr_prepare_rx(struct gelic_card *card,
   376                                    struct gelic_descr *descr)
   377  {
   378          static const unsigned int rx_skb_size =
   379                  ALIGN(GELIC_NET_MAX_FRAME, GELIC_NET_RXBUF_ALIGN) +
   380                  GELIC_NET_RXBUF_ALIGN - 1;
   381          dma_addr_t cpu_addr;
   382          int offset;
   383  
   384          if (gelic_descr_get_status(descr) !=  GELIC_DESCR_DMA_NOT_IN_USE)
   385                  dev_info(ctodev(card), "%s: ERROR status\n", __func__);
   386  
   387          descr->skb = netdev_alloc_skb(*card->netdev, rx_skb_size);
   388          if (!descr->skb) {
   389                  descr->hw_regs.payload.dev_addr = 0; /* tell DMAC don't touch memory */
   390                  return -ENOMEM;
   391          }
   392          descr->hw_regs.dmac_cmd_status = 0;
   393          descr->hw_regs.result_size = 0;
   394          descr->hw_regs.valid_size = 0;
   395          descr->hw_regs.data_error = 0;
   396          descr->hw_regs.payload.dev_addr = 0;
   397          descr->hw_regs.payload.size = 0;
   398          descr->skb = NULL;
                ^^^^^^^^^^^^^^^^^^
NULL

   399  
   400          offset = ((unsigned long)descr->skb->data) &
                                         ^^^^^^^^^^^^
Dereferenced here.

   401                  (GELIC_NET_RXBUF_ALIGN - 1);
   402          if (offset)
   403                  skb_reserve(descr->skb, GELIC_NET_RXBUF_ALIGN - offset);
   404          /* io-mmu-map the skb */
   405          cpu_addr = dma_map_single(ctodev(card), descr->skb->data,
   406                                    GELIC_NET_MAX_FRAME, DMA_FROM_DEVICE);

regards,
dan carpenter