sk_buff 结构体

Question

在wifi驱动中使用到了 内核sk_buff为元素的一个双向链表msdu_list， 在使用过程中

static inline void
ol_rx_mpdu_list_next(
    struct ol_txrx_pdev_t *pdev,
    void *mpdu_list,
    adf_nbuf_t *mpdu_tail,
    adf_nbuf_t *next_mpdu)
{
    htt_pdev_handle htt_pdev = pdev->htt_pdev;
    adf_nbuf_t msdu;

    /*
     * For now, we use a simply flat list of MSDUs.
     * So, traverse the list until we reach the last MSDU within the MPDU.
     */
    TXRX_ASSERT2(mpdu_list);
    msdu = mpdu_list;
    while (!htt_rx_msdu_desc_completes_mpdu(
                htt_pdev, htt_rx_msdu_desc_retrieve(htt_pdev, msdu)))
    {
        msdu = adf_nbuf_next(msdu);
        TXRX_ASSERT2(msdu);
    }
    /* msdu now points to the last MSDU within the first MPDU */
    *mpdu_tail = msdu;
    *next_mpdu = adf_nbuf_next(msdu);
}

msdu = adf_nbuf_next(msdu) = msdu->next; //不断的取下一个，出现问题是：突然取得一个next被污染了，变成NULL或这是 野指针。

出错在htt_rx_msdu_desc_retrieve(htt_pdev, msdu)这一句，读取msdu的data指针。

<4>[350481.729138] Error: get encrypted from a not-first msdu.
<4>[350481.729165] Error: get pn from a not-first msdu.
<4>[350481.729189] Error: get encrypted from a not-first msdu.
<4>[350481.729197] Error: get pn from a not-first msdu.
<4>[350481.729206] Error: get encrypted from a not-first msdu.
<4>[350481.729213] Error: get pn from a not-first msdu.
<1>[350481.729244] Unable to handle kernel NULL pointer dereference at virtual address 000000d8
<1>[350481.729255] pgd = ffffff8009526000
<1>[350481.729263] [000000d8] *pgd=000000007fffe003, *pud=000000007fffe003, *pmd=0000000000000000
<0>[350481.729288] Internal error: Oops: 96000005 [#1] PREEMPT SMP
<4>[350481.729299] Modules linked in: wlan(O) smsc9500(O) smscusbnet(O) cec(O) pstnaud(O) cmbs_audio(O) dsplink(O) hpdev(O) cmac(O) kpcie(O) emac_usb(O) emac(O) msgkit(O) keypad(O) kbase(O) midgard_kbase [last unloaded: wlan]
<4>[350481.729388] CPU: 1 PID: 5363 Comm: AR6K RxCompleti Tainted: G           O    4.4.167 #116
<4>[350481.729397] Hardware name: Rockchip RK3399 Board rev2 (BOX) (DT)
<4>[350481.729406] task: ffffffc045ca1b80 task.stack: ffffffc03849c000
<4>[350481.732523] PC is at htt_rx_msdu_desc_retrieve_hl+0x0/0x8 [wlan]
<4>[350481.735600] LR is at ol_rx_pn_check_base+0x194/0x498 [wlan]
<4>[350481.735619] pc : [<ffffff800106acc4>] lr : [<ffffff800103bff4>] pstate: 404001c5
<4>[350481.735627] sp : ffffffc03849f920
<4>[350481.735635] x29: ffffffc03849f970 x28: ffffff80012c92c8 
<4>[350481.735651] x27: 0000000000000000 x26: ffffffc03e5be230 
<4>[350481.735666] x25: ffffffc03a4e0000 x24: 0000000000000000 
<4>[350481.735680] x23: ffffffc0747fe900 x22: ffffffc057522500 
<4>[350481.735695] x21: ffffffc0575c0000 x20: ffffffc068aea200 
<4>[350481.735709] x19: ffffffc03e5d5000 x18: ffffff80892d2ba7 
<4>[350481.735724] x17: 0000000000000000 x16: ffffff80082137e8 
<4>[350481.735738] x15: 0000000000000000 x14: 00000000000b207d 
<4>[350481.735752] x13: 000000000000000a x12: 0000000000000030 
<4>[350481.735766] x11: 00000000fffffffe x10: ffffff80092d2bb0 
<4>[350481.735781] x9 : 0000000005f5e0ff x8 : 0000000000000000 
<4>[350481.735796] x7 : 0000000000000000 x6 : ffffffc03cee4500 
<4>[350481.735809] x5 : ffffff80012c9338 x4 : ffffff800106acc4 
<4>[350481.735824] x3 : ffffff800106ac00 x2 : 0000000000000004 
<4>[350481.735839] x1 : 0000000000000000 x0 : ffffffc067366c00 

1、有没有什么办法通过crash堆栈找到是什么污染了？

2、如何规避这样的问题？不能直接死机。最好可以在应用层不感知的情况下？空指针比较好判断，但是野指针有点头大。

Answer 1

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