Commit 4acf6c0b authored by Brenden Blanco's avatar Brenden Blanco Committed by David S. Miller
Browse files

bpf: enable direct packet data write for xdp progs 



For forwarding to be effective, XDP programs should be allowed to
rewrite packet data.

This requires that the drivers supporting XDP must all map the packet
memory as TODEVICE or BIDIRECTIONAL before invoking the program.

Signed-off-by: default avatarBrenden Blanco <bblanco@plumgrid.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9ecc2d86

kernel/bpf/verifier.c

+16 −1
Original line number Diff line number Diff line
@@ -653,6 +653,16 @@ static int check_map_access(struct verifier_env *env, u32 regno, int off, 


#define MAX_PACKET_OFF 0xffff



static bool may_write_pkt_data(enum bpf_prog_type type)

{

	switch (type) {

	case BPF_PROG_TYPE_XDP:

		return true;

	default:

		return false;

	}

}



static int check_packet_access(struct verifier_env *env, u32 regno, int off,

			       int size)

{
@@ -806,10 +816,15 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off, 
			err = check_stack_read(state, off, size, value_regno);

		}

	} else if (state->regs[regno].type == PTR_TO_PACKET) {

		if (t == BPF_WRITE) {

		if (t == BPF_WRITE && !may_write_pkt_data(env->prog->type)) {

			verbose("cannot write into packet\n");

			return -EACCES;

		}

		if (t == BPF_WRITE && value_regno >= 0 &&

		    is_pointer_value(env, value_regno)) {

			verbose("R%d leaks addr into packet\n", value_regno);

			return -EACCES;

		}

		err = check_packet_access(env, regno, off, size);

		if (!err && t == BPF_READ && value_regno >= 0)

			mark_reg_unknown_value(state->regs, value_regno);

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