bpf: Fix XDP FD-based attach/detach logic around XDP_FLAGS_UPDATE_IF_NOEXIST (068d9d1e) · Commits · 戴 / test

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: ("bpf, xdp: Extract common XDP program attachment logic") Reported-by:

Stanislav Fomichev <sdf@google.com> Signed-off-by:

Andrii Nakryiko <andriin@fb.com> Signed-off-by:

Alexei Starovoitov <ast@kernel.org> Tested-by:

Stanislav Fomichev <sdf@google.com> Acked-by:

Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/bpf/20200812022923.1217922-1-andriin@fb.com

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;

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