bpf: verifier: reorder stack size check with dead code sanitization

Reorder the calls to check_max_stack_depth() and sanitize_dead_code()
to separate functions which can rewrite instructions from pure checks.

No functional changes.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

kernel/bpf/verifier.c

@@ -6982,12 +6982,13 @@ skip_full_check:
 	while (!pop_stack(env, NULL, NULL));
 	free_states(env);
 
-	if (ret == 0)
-		sanitize_dead_code(env);
-
 	if (ret == 0)
 		ret = check_max_stack_depth(env);
 
+	/* instruction rewrites happen after this point */
+	if (ret == 0)
+		sanitize_dead_code(env);
+
 	if (ret == 0)
 		/* program is valid, convert *(u32*)(ctx + off) accesses */
 		ret = convert_ctx_accesses(env);