Steffen Klassert 0152eee6fc xfrm: Fix NULL pointer dereference in xfrm_input when skb_dst_force clears the dst_entry. ...

Since commit 222d7dbd25 ("net: prevent dst uses after free")
skb_dst_force() might clear the dst_entry attached to the skb.
The xfrm code doesn't expect this to happen, so we crash with
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 case the dst_entry was cleared. We also
move the skb_dst_force() to a codepath that is not used when
the transformation was offloaded, because in this case we
don't have a dst_entry attached to the skb.

The output and forwarding path was already fixed by
commit 9e14379378 ("xfrm: Fix NULL pointer dereference when
skb_dst_force clears the dst_entry.")

Fixes: 222d7dbd25 ("net: prevent dst uses after free")
Reported-by: Jean-Philippe Menil <jpmenil@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

2018-11-22 10:09:39 +01:00

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