detect when pthread_cond_t is moved

Mandragorian · Mandragorian · commit b1aaf1a7886d · 2024-09-14T18:53:21.000+02:00
Closes #3749
diff --git a/src/concurrency/sync.rs b/src/concurrency/sync.rs
@@ -134,6 +134,9 @@ struct Condvar {
     /// Contains the clock of the last thread to
     /// perform a condvar-signal.
     clock: VClock,
+
+    /// Additional data that can be set by shim implementations.
+    data: Option<Box<dyn Any>>,
 }
 
 /// The futex state.
@@ -344,21 +347,49 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         this.machine.sync.rwlocks[id].data.as_deref().and_then(|p| p.downcast_ref::<T>())
     }
 
+    /// Eagerly create and initialize a new condvar.
+    fn condvar_create(
+        &mut self,
+        condvar: &MPlaceTy<'tcx>,
+        offset: u64,
+        data: Option<Box<dyn Any>>,
+    ) -> InterpResult<'tcx, CondvarId> {
+        let this = self.eval_context_mut();
+        this.create_id(
+            condvar,
+            offset,
+            |ecx| &mut ecx.machine.sync.condvars,
+            Condvar { data, ..Default::default() },
+        )
+    }
+
     fn condvar_get_or_create_id(
         &mut self,
         lock: &MPlaceTy<'tcx>,
         offset: u64,
+        initialize_data: impl for<'a> FnOnce(
+            &'a mut MiriInterpCx<'tcx>,
+        ) -> InterpResult<'tcx, Option<Box<dyn Any>>>,
     ) -> InterpResult<'tcx, CondvarId> {
         let this = self.eval_context_mut();
         this.get_or_create_id(
             lock,
             offset,
             |ecx| &mut ecx.machine.sync.condvars,
-            |_| Ok(Default::default()),
+            |ecx| initialize_data(ecx).map(|data| Condvar { data, ..Default::default() }),
         )?
         .ok_or_else(|| err_ub_format!("condvar has invalid ID").into())
     }
 
+    /// Retrieve the additional data stored for a condvar.
+    fn condvar_get_data<'a, T: 'static>(&'a mut self, id: CondvarId) -> Option<&'a T>
+    where
+        'tcx: 'a,
+    {
+        let this = self.eval_context_ref();
+        this.machine.sync.condvars[id].data.as_deref().and_then(|p| p.downcast_ref::<T>())
+    }
+
     #[inline]
     /// Get the id of the thread that currently owns this lock.
     fn mutex_get_owner(&mut self, id: MutexId) -> ThreadId {
diff --git a/src/shims/unix/sync.rs b/src/shims/unix/sync.rs
@@ -206,7 +206,7 @@ fn translate_kind<'tcx>(ecx: &MiriInterpCx<'tcx>, kind: i32) -> InterpResult<'tc
 // - id: u32
 
 #[derive(Debug)]
-/// Additional data that may be used by shim implementations.
+/// Additional data that we attach with each rwlock instance.
 pub struct AdditionalRwLockData {
     /// The address of the rwlock.
     pub address: u64,
@@ -286,6 +286,19 @@ fn condattr_get_clock_id<'tcx>(
     .to_i32()
 }
 
+fn translate_clock_id<'tcx>(ecx: &MiriInterpCx<'tcx>, raw_id: i32) -> InterpResult<'tcx, ClockId> {
+    // To ensure compatibility with PTHREAD_COND_INITIALIZER on all platforms,
+    // we can't just compare with CLOCK_REALTIME: on Solarish, PTHREAD_COND_INITIALIZER
+    // makes the clock 0 but CLOCK_REALTIME is 3.
+    Ok(if raw_id == ecx.eval_libc_i32("CLOCK_REALTIME") || raw_id == 0 {
+        ClockId::Realtime
+    } else if raw_id == ecx.eval_libc_i32("CLOCK_MONOTONIC") {
+        ClockId::Monotonic
+    } else {
+        throw_unsup_format!("unsupported clock id: {raw_id}");
+    })
+}
+
 fn condattr_set_clock_id<'tcx>(
     ecx: &mut MiriInterpCx<'tcx>,
     attr_ptr: &OpTy<'tcx>,
@@ -331,16 +344,6 @@ fn cond_id_offset<'tcx>(ecx: &MiriInterpCx<'tcx>) -> InterpResult<'tcx, u64> {
     Ok(offset)
 }
 
-/// Determines whether this clock represents the real-time clock, CLOCK_REALTIME.
-fn is_cond_clock_realtime<'tcx>(ecx: &MiriInterpCx<'tcx>, clock_id: i32) -> bool {
-    // To ensure compatibility with PTHREAD_COND_INITIALIZER on all platforms,
-    // we can't just compare with CLOCK_REALTIME: on Solarish, PTHREAD_COND_INITIALIZER
-    // makes the clock 0 but CLOCK_REALTIME is 3.
-    // However, we need to always be able to distinguish this from CLOCK_MONOTONIC.
-    clock_id == ecx.eval_libc_i32("CLOCK_REALTIME")
-        || (clock_id == 0 && clock_id != ecx.eval_libc_i32("CLOCK_MONOTONIC"))
-}
-
 fn cond_clock_offset<'tcx>(ecx: &MiriInterpCx<'tcx>) -> u64 {
     // macOS doesn't have a clock attribute, but to keep the code uniform we store
     // a clock ID in the pthread_cond_t anyway. There's enough space.
@@ -355,34 +358,57 @@ fn cond_clock_offset<'tcx>(ecx: &MiriInterpCx<'tcx>) -> u64 {
             .offset(Size::from_bytes(offset), ecx.machine.layouts.i32, ecx)
             .unwrap();
         let id = ecx.read_scalar(&id_field).unwrap().to_i32().unwrap();
+        let id = translate_clock_id(ecx, id).expect("static initializer should be valid");
         assert!(
-            is_cond_clock_realtime(ecx, id),
+            matches!(id, ClockId::Realtime),
             "PTHREAD_COND_INITIALIZER is incompatible with our pthread_cond layout: clock is not CLOCK_REALTIME"
         );
     }
 
     offset
 }
 
+#[derive(Debug, Clone, Copy)]
+enum ClockId {
+    Realtime,
+    Monotonic,
+}
+
+#[derive(Debug)]
+/// Additional data that we attach with each cond instance.
+struct AdditionalCondData {
+    /// The address of the cond.
+    address: u64,
+
+    /// The clock id of the cond.
+    clock_id: ClockId,
+}
+
 fn cond_get_id<'tcx>(
     ecx: &mut MiriInterpCx<'tcx>,
     cond_ptr: &OpTy<'tcx>,
 ) -> InterpResult<'tcx, CondvarId> {
     let cond = ecx.deref_pointer(cond_ptr)?;
-    ecx.condvar_get_or_create_id(&cond, cond_id_offset(ecx)?)
-}
+    let address = cond.ptr().addr().bytes();
+    let id = ecx.condvar_get_or_create_id(&cond, cond_id_offset(ecx)?, |ecx| {
+        let raw_id = if ecx.tcx.sess.target.os == "macos" {
+            ecx.eval_libc_i32("CLOCK_REALTIME")
+        } else {
+            cond_get_clock_id(ecx, cond_ptr)?
+        };
+        let clock_id = translate_clock_id(ecx, raw_id)?;
+        Ok(Some(Box::new(AdditionalCondData { address, clock_id })))
+    })?;
 
-fn cond_reset_id<'tcx>(
-    ecx: &mut MiriInterpCx<'tcx>,
-    cond_ptr: &OpTy<'tcx>,
-) -> InterpResult<'tcx, ()> {
-    ecx.deref_pointer_and_write(
-        cond_ptr,
-        cond_id_offset(ecx)?,
-        Scalar::from_i32(0),
-        ecx.libc_ty_layout("pthread_cond_t"),
-        ecx.machine.layouts.u32,
-    )
+    // Check that the mutex has not been moved since last use.
+    let data = ecx
+        .condvar_get_data::<AdditionalCondData>(id)
+        .expect("data should always exist for pthreads");
+    if data.address != address {
+        throw_ub_format!("pthread_cond_t can't be moved after first use")
+    }
+
+    Ok(id)
 }
 
 fn cond_get_clock_id<'tcx>(
@@ -398,20 +424,6 @@ fn cond_get_clock_id<'tcx>(
     .to_i32()
 }
 
-fn cond_set_clock_id<'tcx>(
-    ecx: &mut MiriInterpCx<'tcx>,
-    cond_ptr: &OpTy<'tcx>,
-    clock_id: i32,
-) -> InterpResult<'tcx, ()> {
-    ecx.deref_pointer_and_write(
-        cond_ptr,
-        cond_clock_offset(ecx),
-        Scalar::from_i32(clock_id),
-        ecx.libc_ty_layout("pthread_cond_t"),
-        ecx.machine.layouts.i32,
-    )
-}
-
 impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
 pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     fn pthread_mutexattr_init(&mut self, attr_op: &OpTy<'tcx>) -> InterpResult<'tcx, ()> {
@@ -820,11 +832,15 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         } else {
             condattr_get_clock_id(this, attr_op)?
         };
-
-        // Write 0 to use the same code path as the static initializers.
-        cond_reset_id(this, cond_op)?;
-
-        cond_set_clock_id(this, cond_op, clock_id)?;
+        let clock_id = translate_clock_id(this, clock_id)?;
+
+        let cond = this.deref_pointer(cond_op)?;
+        let address = cond.ptr().addr().bytes();
+        this.condvar_create(
+            &cond,
+            cond_id_offset(this)?,
+            Some(Box::new(AdditionalCondData { address, clock_id })),
+        )?;
 
         Ok(())
     }
@@ -879,7 +895,10 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let mutex_id = mutex_get_id(this, mutex_op)?;
 
         // Extract the timeout.
-        let clock_id = cond_get_clock_id(this, cond_op)?;
+        let clock_id = this
+            .condvar_get_data::<AdditionalCondData>(id)
+            .expect("additional data should always be present for pthreads")
+            .clock_id;
         let duration = match this
             .read_timespec(&this.deref_pointer_as(abstime_op, this.libc_ty_layout("timespec"))?)?
         {
@@ -890,13 +909,12 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 return Ok(());
             }
         };
-        let timeout_clock = if is_cond_clock_realtime(this, clock_id) {
-            this.check_no_isolation("`pthread_cond_timedwait` with `CLOCK_REALTIME`")?;
-            TimeoutClock::RealTime
-        } else if clock_id == this.eval_libc_i32("CLOCK_MONOTONIC") {
-            TimeoutClock::Monotonic
-        } else {
-            throw_unsup_format!("unsupported clock id: {}", clock_id);
+        let timeout_clock = match clock_id {
+            ClockId::Realtime => {
+                this.check_no_isolation("`pthread_cond_timedwait` with `CLOCK_REALTIME`")?;
+                TimeoutClock::RealTime
+            }
+            ClockId::Monotonic => TimeoutClock::Monotonic,
         };
 
         this.condvar_wait(
@@ -912,17 +930,16 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     }
 
     fn pthread_cond_destroy(&mut self, cond_op: &OpTy<'tcx>) -> InterpResult<'tcx, ()> {
+        //NOTE: Destroying an uninit pthread_cond is UB. Make sure it's not uninit,
+        // by accessing at least once all of its fields that we use.
+
         let this = self.eval_context_mut();
 
         let id = cond_get_id(this, cond_op)?;
         if this.condvar_is_awaited(id) {
             throw_ub_format!("destroying an awaited conditional variable");
         }
 
-        // Destroying an uninit pthread_cond is UB, so check to make sure it's not uninit.
-        cond_get_id(this, cond_op)?;
-        cond_get_clock_id(this, cond_op)?;
-
         // This might lead to false positives, see comment in pthread_mutexattr_destroy
         this.write_uninit(&this.deref_pointer_as(cond_op, this.libc_ty_layout("pthread_cond_t"))?)?;
         // FIXME: delete interpreter state associated with this condvar.
diff --git a/tests/fail-dep/concurrency/libc_pthread_cond_move.init.stderr b/tests/fail-dep/concurrency/libc_pthread_cond_move.init.stderr
@@ -0,0 +1,20 @@
+error: Undefined Behavior: pthread_cond_t can't be moved after first use
+  --> $DIR/libc_pthread_cond_move.rs:LL:CC
+   |
+LL |         libc::pthread_cond_destroy(cond2.as_mut_ptr());
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pthread_cond_t can't be moved after first use
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `check` at $DIR/libc_pthread_cond_move.rs:LL:CC
+note: inside `main`
+  --> $DIR/libc_pthread_cond_move.rs:LL:CC
+   |
+LL |     check()
+   |     ^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/tests/fail-dep/concurrency/libc_pthread_cond_move.rs b/tests/fail-dep/concurrency/libc_pthread_cond_move.rs
@@ -0,0 +1,37 @@
+//@revisions: static_initializer init
+//@ignore-target-windows: No pthreads on Windows
+
+/// Test that moving a pthread_cond between uses fails.
+
+fn main() {
+    check()
+}
+
+#[cfg(init)]
+fn check() {
+    unsafe {
+        use core::mem::MaybeUninit;
+        let mut cond = MaybeUninit::<libc::pthread_cond_t>::uninit();
+
+        libc::pthread_cond_init(cond.as_mut_ptr(), std::ptr::null());
+
+        // move pthread_cond_t
+        let mut cond2 = cond;
+
+        libc::pthread_cond_destroy(cond2.as_mut_ptr()); //~[init] ERROR: pthread_cond_t can't be moved after first use
+    }
+}
+
+#[cfg(static_initializer)]
+fn check() {
+    unsafe {
+        let mut cond = libc::PTHREAD_COND_INITIALIZER;
+
+        libc::pthread_cond_signal(&mut cond as *mut _);
+
+        // move pthread_cond_t
+        let mut cond2 = cond;
+
+        libc::pthread_cond_destroy(&mut cond2 as *mut _); //~[static_initializer] ERROR: pthread_cond_t can't be moved after first use
+    }
+}
diff --git a/tests/fail-dep/concurrency/libc_pthread_cond_move.static_initializer.stderr b/tests/fail-dep/concurrency/libc_pthread_cond_move.static_initializer.stderr
@@ -0,0 +1,20 @@
+error: Undefined Behavior: pthread_cond_t can't be moved after first use
+  --> $DIR/libc_pthread_cond_move.rs:LL:CC
+   |
+LL |         libc::pthread_cond_destroy(&mut cond2 as *mut _);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pthread_cond_t can't be moved after first use
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `check` at $DIR/libc_pthread_cond_move.rs:LL:CC
+note: inside `main`
+  --> $DIR/libc_pthread_cond_move.rs:LL:CC
+   |
+LL |     check()
+   |     ^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
