Commit 068d9d1e authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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bpf: Fix XDP FD-based attach/detach logic around XDP_FLAGS_UPDATE_IF_NOEXIST 



Enforce XDP_FLAGS_UPDATE_IF_NOEXIST only if new BPF program to be attached is
non-NULL (i.e., we are not detaching a BPF program).

Fixes: d4baa936 ("bpf, xdp: Extract common XDP program attachment logic")
Reported-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Tested-by: default avatarStanislav Fomichev <sdf@google.com>
Acked-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20200812022923.1217922-1-andriin@fb.com
parent da7bdfdd

net/core/dev.c

+4 −4
Original line number Diff line number Diff line
@@ -8913,10 +8913,6 @@ static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack 
		NL_SET_ERR_MSG(extack, "Active program does not match expected");

		return -EEXIST;

	}

	if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) && cur_prog) {

		NL_SET_ERR_MSG(extack, "XDP program already attached");

		return -EBUSY;

	}



	/* put effective new program into new_prog */

	if (link)
@@ -8927,6 +8923,10 @@ static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack 
		enum bpf_xdp_mode other_mode = mode == XDP_MODE_SKB

					       ? XDP_MODE_DRV : XDP_MODE_SKB;



		if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) && cur_prog) {

			NL_SET_ERR_MSG(extack, "XDP program already attached");

			return -EBUSY;

		}

		if (!offload && dev_xdp_prog(dev, other_mode)) {

			NL_SET_ERR_MSG(extack, "Native and generic XDP can't be active at the same time");

			return -EEXIST;