Mark r0 as initialized by call

Signed-off-by: Alan Jowett <alan.jowett@microsoft.com>
iovisor · May 7, 2024 · 621d21f · 621d21f
1 parent 4a436d2
commit 621d21f
Showing 1 changed file with 10 additions and 0 deletions.
diff --git a/vm/ubpf_vm.c b/vm/ubpf_vm.c
@@ -539,6 +539,16 @@ ubpf_validate_shadow_register(const struct ubpf_vm* vm, uint16_t* shadow_registe
         *shadow_registers |= 1 << inst.dst;
     }
 
+    if (inst.opcode == EBPF_OP_CALL) {
+        // Mark the return address register as initialized.
+        *shadow_registers |= 1 << 0;
+    }
+
+    if (inst.opcode == EBPF_OP_EXIT && !(*shadow_registers & (1 << 0))) {
+        vm->error_printf(stderr, "Error: Return address register r0 is not initialized.\n");
+        return false;
+    }
+
     return true;
 }