bpf: Clarify get_outer_instance() handling in propagate_to_outer_instance()

propagate_to_outer_instance() calls get_outer_instance() and uses the
returned pointer to reset and commit stack write marks. Under normal
conditions, update_instance() guarantees that an outer instance exists,
so get_outer_instance() cannot return an ERR_PTR.

However, explicitly checking for IS_ERR(outer_instance) makes this code
more robust and self-documenting. It reduces cognitive load when reading
the control flow and silences potential false-positive reports from
static analysis or automated tooling.

No functional change intended.

Signed-off-by: Shardul Bankar <shardulsb08@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251021080849.860072-1-shardulsb08@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/liveness.c b/kernel/bpf/liveness.c
index 1e6538f59a78601a92e4286f94dcced32cc03528..baa742e6cbb65532f937e636920ae234ed711a93 100644 (file)
--- a/kernel/bpf/liveness.c
+++ b/kernel/bpf/liveness.c
@@ -524,6 +524,8 @@ static int propagate_to_outer_instance(struct bpf_verifier_env *env,
 
        this_subprog_start = callchain_subprog_start(callchain);
        outer_instance = get_outer_instance(env, instance);
+       if (IS_ERR(outer_instance))
+               return PTR_ERR(outer_instance);
        callsite = callchain->callsites[callchain->curframe - 1];
 
        reset_stack_write_marks(env, outer_instance, callsite);