[PATCH bpf-next v5 09/16] bpf: Reject stack arguments in non-JITed programs

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

The interpreter does not understand the bpf register r11
(BPF_REG_PARAMS) used for stack argument addressing. 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>
---
 kernel/bpf/core.c   | 2 +-
 kernel/bpf/fixups.c | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index e7e97ffa2a8b..10c36a74431d 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2555,7 +2555,7 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 		goto finalize;
 
 	if (IS_ENABLED(CONFIG_BPF_JIT_ALWAYS_ON) ||
-	    bpf_prog_has_kfunc_call(fp))
+	    bpf_prog_has_kfunc_call(fp) || fp->aux->stack_arg_depth)
 		jit_needed = true;
 
 	if (!bpf_prog_select_interpreter(fp))
diff --git a/kernel/bpf/fixups.c b/kernel/bpf/fixups.c
index f9233945b0f2..179e17007240 100644
--- a/kernel/bpf/fixups.c
+++ b/kernel/bpf/fixups.c
@@ -1302,6 +1302,12 @@ 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 = 0; i < env->subprog_cnt; i++) {
+		if (env->subprog_info[i].incoming_stack_arg_depth) {
+			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.
-- 
2.52.0