Commit f3a95075 authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

bpf: Allow trampoline re-attach for tracing and lsm programs 



Currently we don't allow re-attaching of trampolines. Once
it's detached, it can't be re-attach even when the program
is still loaded.

Adding the possibility to re-attach the loaded tracing and
lsm programs.

Fixing missing unlock with proper cleanup goto jump reported
by Julia.

Reported-by: default avatarkernel test robot <lkp@intel.com>
Reported-by: default avatarJulia Lawall <julia.lawall@lip6.fr>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarKP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/bpf/20210414195147.1624932-2-jolsa@kernel.org
parent 0ea1041b

kernel/bpf/syscall.c

+17 −6
Original line number Diff line number Diff line
@@ -2650,13 +2650,24 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog, 
	 * - if tgt_prog == NULL when this function was called using the old

	 *   raw_tracepoint_open API, and we need a target from prog->aux

	 *

         * The combination of no saved target in prog->aux, and no target

         * specified on load is illegal, and we reject that here.

	 * - if prog->aux->dst_trampoline and tgt_prog is NULL, the program

	 *   was detached and is going for re-attachment.

	 */

	if (!prog->aux->dst_trampoline && !tgt_prog) {

		err = -ENOENT;

		/*

		 * Allow re-attach for TRACING and LSM programs. If it's

		 * currently linked, bpf_trampoline_link_prog will fail.

		 * EXT programs need to specify tgt_prog_fd, so they

		 * re-attach in separate code path.

		 */

		if (prog->type != BPF_PROG_TYPE_TRACING &&

		    prog->type != BPF_PROG_TYPE_LSM) {

			err = -EINVAL;

			goto out_unlock;

		}

		btf_id = prog->aux->attach_btf_id;

		key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf, btf_id);

	}



	if (!prog->aux->dst_trampoline ||

	    (key && key != prog->aux->dst_trampoline->key)) {

kernel/bpf/trampoline.c

+2 −2
Original line number Diff line number Diff line
@@ -444,7 +444,7 @@ int bpf_trampoline_link_prog(struct bpf_prog *prog, struct bpf_trampoline *tr) 
	tr->progs_cnt[kind]++;

	err = bpf_trampoline_update(tr);

	if (err) {

		hlist_del(&prog->aux->tramp_hlist);

		hlist_del_init(&prog->aux->tramp_hlist);

		tr->progs_cnt[kind]--;

	}

out:
@@ -467,7 +467,7 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr) 
		tr->extension_prog = NULL;

		goto out;

	}

	hlist_del(&prog->aux->tramp_hlist);

	hlist_del_init(&prog->aux->tramp_hlist);

	tr->progs_cnt[kind]--;

	err = bpf_trampoline_update(tr);

out: