Commit dfa74909 authored Apr 12, 2020 by David Ahern Committed by Daniel Borkmann Apr 14, 2020

xdp: Reset prog in dev_change_xdp_fd when fd is negative



The commit mentioned in the Fixes tag reuses the local prog variable
when looking up an expected_fd. The variable is not reset when fd < 0
causing a detach with the expected_fd set to actually call
dev_xdp_install for the existing program. The end result is that the
detach does not happen.

Fixes: 92234c8f ("xdp: Support specifying expected existing program when attaching XDP")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20200412133204.43847-1-dsahern@kernel.org

parent 96b2eb6e

net/core/dev.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -8667,8 +8667,8 @@ int dev_change_xdp_fd(struct net_device dev, struct netlink_ext_ack extack,
		const struct net_device_ops *ops = dev->netdev_ops;
		enum bpf_netdev_command query;
		u32 prog_id, expected_id = 0;
		struct bpf_prog *prog = NULL;
		bpf_op_t bpf_op, bpf_chk;
		struct bpf_prog *prog;
		bool offload;
		int err;

		@@ -8734,6 +8734,7 @@ int dev_change_xdp_fd(struct net_device dev, struct netlink_ext_ack extack,
		} else {
		if (!prog_id)
		return 0;
		prog = NULL;
		}

		err = dev_xdp_install(dev, bpf_op, extack, flags, prog);

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