From: Mykyta Yatsenko The verifier currently enforces a zero return value for all async callbacks—a constraint originally introduced for bpf_timer. That restriction is too narrow for other async use cases. Relax the rule by allowing non-zero return codes from async callbacks in general, while preserving the zero-return requirement for bpf_timer to maintain its existing semantics. Signed-off-by: Mykyta Yatsenko Acked-by: Eduard Zingerman --- kernel/bpf/verifier.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c1b726fb22c8..02b93a54a446 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10789,7 +10789,7 @@ static int set_timer_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_async_callback_fn = true; - callee->callback_ret_range = retval_range(0, 1); + callee->callback_ret_range = retval_range(0, 0); return 0; } @@ -17073,9 +17073,8 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char } if (frame->in_async_callback_fn) { - /* enforce return zero from async callbacks like timer */ exit_ctx = "At async callback return"; - range = retval_range(0, 0); + range = frame->callback_ret_range; goto enforce_retval; } -- 2.51.0