Re: [PATCH bpf-next v3 10/24] bpf: Reject stack arguments in non-JITed programs

[Yonghong Song <yonghong.song@linux.dev>]

On 5/11/26 8:19 AM, bot+bpf-ci@kernel.org wrote:
>> bpf: Reject stack arguments in non-JITed programs
> This isn't a bug, but should this commit include a Fixes: tag? This
> appears to be fixing an issue introduced by commit 3330ee8db989
> ("bpf: Support stack arguments for bpf functions").

There is no need for fix tag. At this point, r11 based
insns are rejected by verifier. So nothing to fix.

>
>> The interpreter does not understand the bpf register r11
>> (BPF_REG_PARAMS) used for stack arguments. So reject interpreter
>> usage if stack arguments are used either in the main program or
>> any subprogram.
>>
>> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
>> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
>> index ae10b9ca018d..958d86f0beac 100644
>> --- a/kernel/bpf/core.c
>> +++ b/kernel/bpf/core.c
>> @@ -2599,7 +2599,7 @@ struct bpf_prog *__bpf_prog_select_runtime(struct bpf_verifier_env *env, struct
>>   		goto finalize;
>>
>>   	if (IS_ENABLED(CONFIG_BPF_JIT_ALWAYS_ON) ||
>> -	    bpf_prog_has_kfunc_call(fp))
>> +	    bpf_prog_has_kfunc_call(fp) || (env && env->subprog_info[0].stack_arg_cnt))
>>   		jit_needed = true;
>>
>>   	if (!bpf_prog_select_interpreter(fp))
>> diff --git a/kernel/bpf/fixups.c b/kernel/bpf/fixups.c
>> index ba86039789fd..19056016eed8 100644
>> --- a/kernel/bpf/fixups.c
>> +++ b/kernel/bpf/fixups.c
>> @@ -1407,6 +1407,12 @@ int bpf_fixup_call_args(struct bpf_verifier_env *env)
>>   		verbose(env, "calling kernel functions are not allowed in non-JITed programs\n");
>>   		return -EINVAL;
>>   	}
>> +	for (i = 1; i < env->subprog_cnt; i++) {
>> +		if (bpf_in_stack_arg_cnt(&env->subprog_info[i])) {
>> +			verbose(env, "stack args are not supported in non-JITed programs\n");
>> +			return -EINVAL;
>> +		}
>> +	}
>>   	if (env->subprog_cnt > 1 && env->prog->aux->tail_call_reachable) {
>>   		/* When JIT fails the progs with bpf2bpf calls and tail_calls
>>   		 * have to be rejected, since interpreter doesn't support them yet.
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25652623893