Commit ddb47d51 authored May 14, 2020 by Jesper Dangaard Brouer Committed by Alexei Starovoitov May 14, 2020

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

parent c8741e2b

net/core/filter.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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;

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