xdp: Clear grow memory in bpf_xdp_adjust_tail()
Clearing memory of tail when grow happens, because it is too easy
to write a XDP_PASS program that extend the tail, which expose
this memory to users that can run tcpdump.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/158945349039.97035.5262100484553494.stgit@firesoul
diff --git a/net/core/filter.c b/net/core/filter.c
index e7b033d..a85eb53 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3427,6 +3427,10 @@ BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)
if (unlikely(data_end < xdp->data + ETH_HLEN))
return -EINVAL;
+ /* Clear memory area on grow, can contain uninit kernel memory */
+ if (offset > 0)
+ memset(xdp->data_end, 0, offset);
+
xdp->data_end = data_end;
return 0;