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: 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
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index fd49519..941ca06d 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2648,14 +2648,25 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
* target_btf_id using the link_create API.
*
* - 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.
+ * raw_tracepoint_open API, and we need a target from prog->aux
+ *
+ * - 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;
- 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 ||