Subject: Re: Unable to handle kernel NULL pointer dereference at 0000000000000088 RIP: [<ffffffff881ba167>] :bnx2:bnx2_poll_work+0xc7/0x1253

From: Joe Jin <[email-masked]>
Date: Wed, 15 Oct 2014 11:29:14 +0800

Copy to new maintainer from QLogic and netdev.

Thanks,
Joe
On 10/11/14 17:22, zheng.li wrote:
> Hi Michael,
> I encounter a null pointer in bnx2_poll_work，
> after analyzed the vmcore found:
> tx_prod = 27708 and hw_cons = bnx2_get_hw_tx_cons(bnapi) = 27722;
> hw_cons > tx_prod;
> so the root cause is mostly HW sent data count is larger than stack
> provide in bnx2_start_xmit to cause memory override, normally HW just
> can sent data maximum is tx_prod, but don't know why HW sent data more
> than tx_prod 14 data.
> 
> Can you help to look at the issue? we encounter several times.
> bnx2 driver is 2.1.11,
> #define DRV_MODULE_VERSION	"2.1.11"
> #define DRV_MODULE_RELDATE	"July 20, 2011"
> Kernel version is : 2.6.18-371.1.2.0.1
> 
> 
> vmcore show infor is below:
> 
> crash64> bnx2 ffff81122c650500
> struct bnx2 {
>   regview = 0xffffc200100e0000,
>   dev = 0xffff81122c650000,
>   pdev = 0xffff81122f0c9000,
>   intr_sem = {
>     counter = 0
>   },
>   flags = 22404,
>   bnx2_napi = {{
>       dummy_netdev = 0xffff81242ae3e800,
>       bp = 0xffff81122c650500,
>       status_blk = {
>         msi = 0xffff81122391b000,
>         msix = 0xffff81122391b000
>       },
>       hw_tx_cons_ptr = 0xffff81122391b00a,
>       hw_rx_cons_ptr = 0xffff81122391b012,
>       last_status_idx = 65048,
>       int_num = 0,
>       cnic_tag = 0,
>       cnic_present = 0,
>       rx_ring = {
>         rx_prod_bseq = 1540471240,
>         rx_prod = 21188,
>         rx_cons = 20932,
>         rx_bidx_addr = 65540,
>         rx_bseq_addr = 65544,
>         rx_pg_bidx_addr = 65604,
>         rx_pg_prod = 0,
>         rx_pg_cons = 0,
>         rx_buf_ring = 0xffffc20014a7b000,
>         rx_desc_ring = {0xffff81122b8a0000, 0x0, 0x0, 0x0, 0x0, 0x0,
> 0x0, 0x0},
>         rx_pg_ring = 0x0,
>         rx_pg_desc_ring = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
>         rx_desc_mapping = {78039875584, 0, 0, 0, 0, 0, 0, 0},
>         rx_pg_desc_mapping = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
>       },
>       tx_ring = {
>         tx_prod_bseq = 3702584042,
>         tx_prod = 27708,
>         tx_bidx_addr = 69768,
>         tx_bseq_addr = 69776,
>         tx_desc_ring = 0xffff811227890000,
>         tx_buf_ring = 0xffff81242f510000,
>         tx_cons = 27603,
>         hw_tx_cons = 27603,
>         tx_desc_mapping = 77972701184
>       }
>     },
> 
> crash64> rd 0xffff81122391b00a
> ffff81122391b00a:  0000000000006c4a
> hw_cons = 6c4a = 27722;
> 
> usr/src/debug/kernel-2.6.18/linux-2.6.18-371.1.2.0.1.el5.x86_64/include/linux/skbuff.h:
> 921
> 0xffffffff881ba167 <bnx2_poll_work+199>:921>:   mov    0x88(%r13),%edx
> R13: 0000000000000000
> R13 is skb which is NULL at that moment.
> 
> Had refer https://access.redhat.com/solutions/341183
> and
> http://kernel.opensuse.org/cgit/kernel/commit/?id=c1f5163de417dab01fa9daaf09a74bbb19303f3c
> but can't exactly know which case our bug hit.
> 
> Thanks,
> James Li
>