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

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Date:   Fri, 11 Jan 2019 17:53:03 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     baijiaju1990@...il.com
Cc:     yanjun.zhu@...cle.com, keescook@...omium.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: nvidia: forcedeth: Fix two possible concurrency
 use-after-free bugs

From: Jia-Ju Bai <baijiaju1990@...il.com>
Date: Tue,  8 Jan 2019 20:45:18 +0800

> 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.

I do not think so, the netif_tx_lock_bh() done will prevent the parallel
execution.