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SubjectRe: [PATCH] net: nvidia: forcedeth: Fix two possible concurrency use-after-free bugs
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On 2019/1/9 9:24, Yanjun Zhu wrote:
>
> On 2019/1/8 20:57, Jia-Ju Bai wrote:
>>
>>
>> On 2019/1/8 20:54, Zhu Yanjun wrote:
>>>
>>> 在 2019/1/8 20:45, Jia-Ju Bai 写道:
>>>> In drivers/net/ethernet/nvidia/forcedeth.c, the functions
>>>> nv_start_xmit() and nv_start_xmit_optimized() can be concurrently
>>>> executed with nv_poll_controller().
>>>>
>>>> nv_start_xmit
>>>> line 2321: prev_tx_ctx->skb = skb;
>>>>
>>>> nv_start_xmit_optimized
>>>> line 2479: prev_tx_ctx->skb = skb;
>>>>
>>>> nv_poll_controller
>>>> nv_do_nic_poll
>>>> line 4134: spin_lock(&np->lock);
>>>> nv_drain_rxtx
>>>> nv_drain_tx
>>>> nv_release_txskb
>>>> line 2004: dev_kfree_skb_any(tx_skb->skb);
>>>>
>>>> Thus, two possible concurrency use-after-free bugs may occur.
>>>>
>>>> To fix these possible bugs,
>>>
>>>
>>> Does this really occur? Can you reproduce this ?
>>
>> This bug is not found by the real execution.
>> It is found by a static tool written by myself, and then I check it
>> by manual code review.
>
> Before "line 2004: dev_kfree_skb_any(tx_skb->skb); ",
>
> "
>
> nv_disable_irq(dev);
> nv_napi_disable(dev);
> netif_tx_lock_bh(dev);
> netif_addr_lock(dev);
> spin_lock(&np->lock);
> /* stop engines */
> nv_stop_rxtx(dev); <---this stop rxtx
> nv_txrx_reset(dev);
> "
>
> In this case, does nv_start_xmit or nv_start_xmit_optimized still work
> well?
>

nv_stop_rxtx() calls nv_stop_tx(dev).

static void nv_stop_tx(struct net_device *dev)
{
struct fe_priv *np = netdev_priv(dev);
u8 __iomem *base = get_hwbase(dev);
u32 tx_ctrl = readl(base + NvRegTransmitterControl);

if (!np->mac_in_use)
tx_ctrl &= ~NVREG_XMITCTL_START;
else
tx_ctrl |= NVREG_XMITCTL_TX_PATH_EN;
writel(tx_ctrl, base + NvRegTransmitterControl);
if (reg_delay(dev, NvRegTransmitterStatus, NVREG_XMITSTAT_BUSY, 0,
NV_TXSTOP_DELAY1, NV_TXSTOP_DELAY1MAX))
netdev_info(dev, "%s: TransmitterStatus remained busy\n",
__func__);

udelay(NV_TXSTOP_DELAY2);
if (!np->mac_in_use)
writel(readl(base + NvRegTransmitPoll) &
NVREG_TRANSMITPOLL_MAC_ADDR_REV,
base + NvRegTransmitPoll);
}

nv_stop_tx() seems to only write registers to stop transmitting for
hardware.
But it does not wait until nv_start_xmit() and nv_start_xmit_optimized()
finish execution.
Maybe netif_stop_queue() should be used here to stop transmitting for
network layer, but this function does not seem to wait, either.
Do you know any function that can wait until ".ndo_start_xmit" finish
execution?


Best wishes,
Jia-Ju Bai


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