netdev - Re: [PATCH 5/6] xfrm: Fix NULL pointer dereference when skb_dst_force clears the dst

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Date:   Mon, 1 Oct 2018 14:29:36 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        David Miller <davem@...emloft.net>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>, netdev@...r.kernel.org
Subject: Re: [PATCH 5/6] xfrm: Fix NULL pointer dereference when skb_dst_force
 clears the dst_entry.

On 10/01/2018 11:58 AM, Steffen Klassert wrote:

> Since commit 222d7dbd258d ("net: prevent dst uses after free")
> skb_dst_force() might clear the dst_entry attached to the skb.
> The xfrm code don't expect this to happen, so we crash with

   Doesn't.

> a NULL pointer dereference in this case. Fix it by checking
> skb_dst(skb) for NULL after skb_dst_force() and drop the packet
> in cast the dst_entry was cleared.

   In case?

> Fixes: 222d7dbd258d ("net: prevent dst uses after free")
> Reported-by: Tobias Hommel <netdev-list@...oetigt.de>
> Reported-by: Kristian Evensen <kristian.evensen@...il.com>
> Reported-by: Wolfgang Walter <linux@...m.de>
> Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
[...]

MBR, Sergei