Commit 19539ce7 authored Sep 10, 2015 by Tycho Andersen Committed by David S. Miller Sep 11, 2015

ebpf: emit correct src_reg for conditional jumps



Instead of always emitting BPF_REG_X, let's emit BPF_REG_X only when the
source actually is BPF_X. This causes programs generated by the classic
converter to not be importable via bpf(), as the eBPF verifier checks that
the src_reg is correct or 0. While not a problem yet, this will be a
problem when BPF_PROG_DUMP lands, and we can potentially dump and re-import
programs generated by the converter.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
CC: Alexei Starovoitov <ast@kernel.org>
CC: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 1853c949

net/core/filter.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -478,9 +478,9 @@ static int bpf_convert_filter(struct sock_filter *prog, int len,
	bpf_src = BPF_X;		bpf_src = BPF_X;
	} else {		} else {
	insn->dst_reg = BPF_REG_A;		insn->dst_reg = BPF_REG_A;
	insn->src_reg = BPF_REG_X;
	insn->imm = fp->k;		insn->imm = fp->k;
	bpf_src = BPF_SRC(fp->code);		bpf_src = BPF_SRC(fp->code);
			insn->src_reg = bpf_src == BPF_X ? BPF_REG_X : 0;
	}		}

	/* Common case where 'jump_false' is next insn. */		/* Common case where 'jump_false' is next insn. */