linux-kernel - Re: [PATCH v3] myri10ge: fix an incorrect free for skb in myri10ge_sw

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Date:   Wed, 6 Apr 2022 10:50:33 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Xiaomeng Tong <xiam0nd.tong@...il.com>
Cc:     christopher.lee@...i.com, davem@...emloft.net, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] myri10ge: fix an incorrect free for skb in
 myri10ge_sw_tso

On Wed,  6 Apr 2022 11:55:56 +0800 Xiaomeng Tong wrote:
> All remaining skbs should be released when myri10ge_xmit fails to
> transmit a packet. Fix it within another skb_list_walk_safe.

I think it was also a UAF.

> diff --git a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
> index 50ac3ee2577a..21d2645885ce 100644
> --- a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
> +++ b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
> @@ -2903,11 +2903,9 @@ static netdev_tx_t myri10ge_sw_tso(struct sk_buff *skb,
>  		status = myri10ge_xmit(curr, dev);
>  		if (status != 0) {
>  			dev_kfree_skb_any(curr);
> -			if (segs != NULL) {
> -				curr = segs;
> -				segs = next;
> +			skb_list_walk_safe(next, curr, next) {
>  				curr->next = NULL;
> -				dev_kfree_skb_any(segs);
> +				dev_kfree_skb_any(curr);
>  			}
>  			goto drop;
>  		}

Much better, thanks. 

kfree_skb_list() exists but the patch was already applied, so whatever.