linux-kernel - Re: [PATCH RFC net] ps3/gelic: Fix possible NULL pointer dereference

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Date: Wed, 21 Feb 2024 21:32:27 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Simon Horman <horms@...nel.org>, Geoff Levand <geoff@...radead.org>
Cc: Geoff Levand <geoff@...radead.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Jeff Garzik <jeff@...zik.org>, netdev@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC net] ps3/gelic: Fix possible NULL pointer dereference

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