Re: [PATCH] net: nvidia: forcedeth: Fix two possible concurrency use-after-free bugs

[Yanjun Zhu]

On 2019/1/8 20:57, Jia-Ju Bai wrote:
> On 2019/1/8 20:54, Zhu Yanjun wrote:
> > å 2019/1/8 20:45, Jia-Ju Bai åé:
> > > 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
> > > ÂÂ line 2321: prev_tx_ctx->skb = skb;
> > >
> > > nv_start_xmit_optimized
> > > ÂÂ line 2479: prev_tx_ctx->skb = skb;
> > >
> > > nv_poll_controller
> > > ÂÂ nv_do_nic_poll
> > > ÂÂÂÂ line 4134: spin_lock(&np->lock);
> > > ÂÂÂÂ nv_drain_rxtx
> > > ÂÂÂÂÂÂ nv_drain_tx
> > > ÂÂÂÂÂÂÂÂ nv_release_txskb
> > > ÂÂÂÂÂÂÂÂÂÂ 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); ",

"

ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ nv_disable_irq(dev);
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ nv_napi_disable(dev);
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ netif_tx_lock_bh(dev);
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ netif_addr_lock(dev);
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ spin_lock(&np->lock);
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /* stop engines */
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ nv_stop_rxtx(dev);ÂÂ <---this stop rxtx
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ nv_txrx_reset(dev);
"

In this case, does nv_start_xmit or nv_start_xmit_optimized still work well?

Zhu Yanjun

> Best wishes,
> Jia-Ju Bai