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

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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: kernel test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: KP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/bpf/20210414195147.1624932-2-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2021-04-14 21:51:41 +02:00 committed by Alexei Starovoitov
parent 0ea1041bfa
commit f3a9507554
2 changed files with 19 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

23
kernel/bpf/syscall.c
View file

@ -2648,14 +2648,25 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
* target_btf_id using the link_create API. * target_btf_id using the link_create API.
* *
* - if tgt_prog == NULL when this function was called using the old * - if tgt_prog == NULL when this function was called using the old
* raw_tracepoint_open API, and we need a target from prog->aux * raw_tracepoint_open API, and we need a target from prog->aux
* *
* The combination of no saved target in prog->aux, and no target * - if prog->aux->dst_trampoline and tgt_prog is NULL, the program
* specified on load is illegal, and we reject that here. * was detached and is going for re-attachment.
*/ */
if (!prog->aux->dst_trampoline && !tgt_prog) { if (!prog->aux->dst_trampoline && !tgt_prog) {
err = -ENOENT; /*
goto out_unlock; * 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 || if (!prog->aux->dst_trampoline ||

4
kernel/bpf/trampoline.c
View file

@ -444,7 +444,7 @@ int bpf_trampoline_link_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
tr->progs_cnt[kind]++; tr->progs_cnt[kind]++;
err = bpf_trampoline_update(tr); err = bpf_trampoline_update(tr);
if (err) { if (err) {
hlist_del(&prog->aux->tramp_hlist); hlist_del_init(&prog->aux->tramp_hlist);
tr->progs_cnt[kind]--; tr->progs_cnt[kind]--;
} }
out: out:
@ -467,7 +467,7 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
tr->extension_prog = NULL; tr->extension_prog = NULL;
goto out; goto out;
} }
hlist_del(&prog->aux->tramp_hlist); hlist_del_init(&prog->aux->tramp_hlist);
tr->progs_cnt[kind]--; tr->progs_cnt[kind]--;
err = bpf_trampoline_update(tr); err = bpf_trampoline_update(tr);
out: out: