netdev - Null pointer dereference in tg3_poll

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Message-ID: <CAO7SqHCqADHoZMy7+quaF83-Ln24A=xx10D1Tv9=SX5DFsncpg@mail.gmail.com>
Date:   Tue, 28 Mar 2017 11:32:40 -0700
From:   Salam Noureddine <noureddine@...sta.com>
To:     Network Development <netdev@...r.kernel.org>
Cc:     mchan@...adcom.com, prashant@...adcom.com, siva.kallam@...adcom.com
Subject: Null pointer dereference in tg3_poll_work running linux-3.4

Hi,

We've seen a very rare kernel panic in tg3_poll_work on hardware
running linux-3.4.
I haven't seen any upstream patches that seem to fix this issue in the
tg3 driver.
The disassembly shows that the panic is happening in tg3_rx which is
inlined into
tg3_poll_work. In the code below, the "data" pointer seem to be Null,

                        tg3_recycle_rx(tnapi, tpr, opaque_key,
                                       desc_idx, *post_ptr);

                        skb = netdev_alloc_skb(tp->dev,
                                               len + TG3_RAW_IP_ALIGN);

                        if (skb == NULL)
                                goto drop_it_no_recycle;

                        skb_reserve(skb, TG3_RAW_IP_ALIGN);
                        pci_dma_sync_single_for_cpu(tp->pdev,
dma_addr, len, PCI_DMA_FROMDEVICE);
                        memcpy(skb->data,
                               data + TG3_RX_OFFSET(tp),
                               len);

                        pci_dma_sync_single_for_device(tp->pdev, dma_addr, len,
PCI_DMA_FROMDEVICE);

I am wondering if anyone has seen this before or if it was fixed and I
missed the patch for it. If not,
any ideas on how we could end up with data being null? I don't have a
reproduction scenario for
this one.

Thanks,

Salam