Check prctl argument types and fix the test.

Author: Vytautas Astrauskas

src/shims/thread.rs

@@ -92,12 +92,26 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         &mut self,
         option: OpTy<'tcx, Tag>,
         arg2: OpTy<'tcx, Tag>,
-        _arg3: OpTy<'tcx, Tag>,
-        _arg4: OpTy<'tcx, Tag>,
-        _arg5: OpTy<'tcx, Tag>,
+        arg3: OpTy<'tcx, Tag>,
+        arg4: OpTy<'tcx, Tag>,
+        arg5: OpTy<'tcx, Tag>,
     ) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();
 
+        // prctl last 5 arguments are declared as variadic. Therefore, we need
+        // to check their types manually.
+        let c_long_size = this.libc_ty_layout("c_long")?.size.bytes();
+        let check_arg = |arg: OpTy<'tcx, Tag>| -> InterpResult<'tcx> {
+            match this.read_scalar(arg)?.not_undef()? {
+                Scalar::Raw { size, .. } if u64::from(size) == c_long_size => Ok(()),
+                _ => throw_ub_format!("an argument of unsupported type was passed to prctl"),
+            }
+        };
+        check_arg(arg2)?;
+        check_arg(arg3)?;
+        check_arg(arg4)?;
+        check_arg(arg5)?;
+
         let option = this.read_scalar(option)?.not_undef()?.to_i32()?;
         if option == this.eval_libc_i32("PR_SET_NAME")? {
             let address = this.read_scalar(arg2)?.not_undef()?;

tests/run-pass/concurrency/libc_prctl_thread_name.rs

@@ -9,9 +9,9 @@ use std::ffi::CString;
 fn main() {
     unsafe {
         let thread_name = CString::new("hello").expect("CString::new failed");
-        assert_eq!(libc::prctl(libc::PR_SET_NAME, thread_name.as_ptr() as u64, 0, 0, 0), 0);
+        assert_eq!(libc::prctl(libc::PR_SET_NAME, thread_name.as_ptr() as libc::c_long, 0 as libc::c_long, 0 as libc::c_long, 0 as libc::c_long), 0);
         let mut buf = [0; 6];
-        assert_eq!(libc::prctl(libc::PR_GET_NAME, buf.as_mut_ptr() as u64, 0, 0, 0), 0);
+        assert_eq!(libc::prctl(libc::PR_GET_NAME, buf.as_mut_ptr() as libc::c_long, 0 as libc::c_long, 0 as libc::c_long, 0 as libc::c_long), 0);
         assert_eq!(thread_name.as_bytes_with_nul(), buf);
     }
 }