Re: [PATCH bpf-next v5 1/5] bpf: Factor out program return value calculation

[kernel test robot <lkp@intel.com>]

Hi Emil,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Emil-Tsalapatis/bpf-Factor-out-program-return-value-calculation/20260227-235723
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20260227154616.6846-2-emil%40etsalapatis.com
patch subject: [PATCH bpf-next v5 1/5] bpf: Factor out program return value calculation
config: arm-randconfig-001-20260228 (https://download.01.org/0day-ci/archive/20260228/202602280948.ZMhck27g-lkp@intel.com/config)
compiler: clang version 16.0.6 (https://github.com/llvm/llvm-project 7cbf1a2591520c2491aa35339f227775f4d3adf6)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260228/202602280948.ZMhck27g-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602280948.ZMhck27g-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/bpf/verifier.c:17864:3: warning: label at end of compound statement is a C2x extension [-Wc2x-extensions]
                   }
                   ^
   kernel/bpf/verifier.c:17923:6: warning: unused variable 'ret' [-Wunused-variable]
           int ret, err;
               ^
   kernel/bpf/verifier.c:17926:7: warning: unused variable 'return_32bit' [-Wunused-variable]
           bool return_32bit = false;
                ^
   3 warnings generated.


vim +17864 kernel/bpf/verifier.c

 17805	
 17806	
 17807	static bool return_retval_range(struct bpf_verifier_env *env, struct bpf_retval_range *range)
 17808	{
 17809		enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
 17810	
 17811		/* Default return value range. */
 17812		*range = retval_range(0, 1);
 17813	
 17814		switch (prog_type) {
 17815		case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
 17816			switch (env->prog->expected_attach_type) {
 17817			case BPF_CGROUP_UDP4_RECVMSG:
 17818			case BPF_CGROUP_UDP6_RECVMSG:
 17819			case BPF_CGROUP_UNIX_RECVMSG:
 17820			case BPF_CGROUP_INET4_GETPEERNAME:
 17821			case BPF_CGROUP_INET6_GETPEERNAME:
 17822			case BPF_CGROUP_UNIX_GETPEERNAME:
 17823			case BPF_CGROUP_INET4_GETSOCKNAME:
 17824			case BPF_CGROUP_INET6_GETSOCKNAME:
 17825			case BPF_CGROUP_UNIX_GETSOCKNAME:
 17826				*range = retval_range(1, 1);
 17827				break;
 17828			case BPF_CGROUP_INET4_BIND:
 17829			case BPF_CGROUP_INET6_BIND:
 17830				*range = retval_range(0, 3);
 17831				break;
 17832			default:
 17833				break;
 17834			}
 17835			break;
 17836		case BPF_PROG_TYPE_CGROUP_SKB:
 17837			if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS)
 17838				*range = retval_range(0, 3);
 17839			break;
 17840		case BPF_PROG_TYPE_CGROUP_SOCK:
 17841		case BPF_PROG_TYPE_SOCK_OPS:
 17842		case BPF_PROG_TYPE_CGROUP_DEVICE:
 17843		case BPF_PROG_TYPE_CGROUP_SYSCTL:
 17844		case BPF_PROG_TYPE_CGROUP_SOCKOPT:
 17845			break;
 17846		case BPF_PROG_TYPE_RAW_TRACEPOINT:
 17847			if (!env->prog->aux->attach_btf_id)
 17848				return false;
 17849			*range = retval_range(0, 0);
 17850			break;
 17851		case BPF_PROG_TYPE_TRACING:
 17852			switch (env->prog->expected_attach_type) {
 17853			case BPF_TRACE_FENTRY:
 17854			case BPF_TRACE_FEXIT:
 17855			case BPF_TRACE_FSESSION:
 17856				*range = retval_range(0, 0);
 17857				break;
 17858			case BPF_TRACE_RAW_TP:
 17859			case BPF_MODIFY_RETURN:
 17860				return false;
 17861			case BPF_TRACE_ITER:
 17862				break;
 17863			default:
 17864			}
 17865			break;
 17866		case BPF_PROG_TYPE_KPROBE:
 17867			switch (env->prog->expected_attach_type) {
 17868			case BPF_TRACE_KPROBE_SESSION:
 17869			case BPF_TRACE_UPROBE_SESSION:
 17870				break;
 17871			default:
 17872				return false;
 17873			}
 17874			break;
 17875		case BPF_PROG_TYPE_SK_LOOKUP:
 17876			*range = retval_range(SK_DROP, SK_PASS);
 17877			break;
 17878	
 17879		case BPF_PROG_TYPE_LSM:
 17880			if (env->prog->expected_attach_type != BPF_LSM_CGROUP) {
 17881				/* no range found, any return value is allowed */
 17882				if (!get_func_retval_range(env->prog, range))
 17883					return false;
 17884				/* no restricted range, any return value is allowed */
 17885				if (range->minval == S32_MIN && range->maxval == S32_MAX)
 17886					return false;
 17887				range->return_32bit = true;
 17888			} else if (!env->prog->aux->attach_func_proto->type) {
 17889				/* Make sure programs that attach to void
 17890				 * hooks don't try to modify return value.
 17891				 */
 17892				*range = retval_range(1, 1);
 17893			}
 17894			break;
 17895	
 17896		case BPF_PROG_TYPE_NETFILTER:
 17897			*range = retval_range(NF_DROP, NF_ACCEPT);
 17898			break;
 17899		case BPF_PROG_TYPE_STRUCT_OPS:
 17900			*range = retval_range(0, 0);
 17901			break;
 17902		case BPF_PROG_TYPE_EXT:
 17903			/* freplace program can return anything as its return value
 17904			 * depends on the to-be-replaced kernel func or bpf program.
 17905			 */
 17906		default:
 17907			return false;
 17908		}
 17909	
 17910		/* Continue calculating. */
 17911	
 17912		return true;
 17913	}
 17914	

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