linux-kernel - Re: [PATCH] ftrace: tracepoint of net_dev

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1306854791.11899.30.camel@gandalf.stny.rr.com>
Date:	Tue, 31 May 2011 11:13:11 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Koki Sanagi <sanagi.koki@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	davem@...emloft.net, nhorman@...driver.com, mingo@...e.hu,
	fweisbec@...il.com, mathieu.desnoyers@...icios.com,
	tglx@...utronix.de, kosaki.motohiro@...fujitsu.com,
	izumi.taku@...fujitsu.com, kaneshige.kenji@...fujitsu.com
Subject: Re: [PATCH] ftrace: tracepoint of net_dev_xmit sees freed skb and
 causes panic

On Tue, 2011-05-31 at 16:48 +0900, Koki Sanagi wrote:
> Because there is a possibility that skb is kfree_skb()ed and zero cleared
> after ndo_start_xmit, we should not see the contents of skb like skb->len and
> skb->dev->name after ndo_start_xmit. But trace_net_dev_xmit does that
> and causes panic by NULL pointer dereference.
> This patch fixes trace_net_dev_xmit not to see the contents of skb directly.


>  
>  	if (likely(!skb->next)) {
>  		u32 features;
> @@ -2139,8 +2140,9 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
>  			}
>  		}
>  
> +		skb_len = skb->len;
>  		rc = ops->ndo_start_xmit(skb, dev);
> -		trace_net_dev_xmit(skb, rc);
> +		trace_net_dev_xmit(skb, rc, dev, skb_len);
>  		if (rc == NETDEV_TX_OK)
>  			txq_trans_update(txq);
>  		return rc;
> @@ -2160,8 +2162,9 @@ gso:
>  		if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
>  			skb_dst_drop(nskb);
>  
> +		skb_len = nskb->len;
>  		rc = ops->ndo_start_xmit(nskb, dev);
> -		trace_net_dev_xmit(nskb, rc);
> +		trace_net_dev_xmit(nskb, rc, dev, skb_len);

What if you just put the tracepoint before the call to
ops->ndo_start_xmit?

-- Steve

>  		if (unlikely(rc != NETDEV_TX_OK)) {
>  			if (rc & ~NETDEV_TX_MASK)
>  				goto out_kfree_gso_skb;


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/