Include spans in use-after-free diagnostics

Author: saethlin

src/diagnostics.rs

@@ -304,11 +304,21 @@ pub fn report_error<'tcx, 'mir>(
                     (None, format!("this usually indicates that your program performed an invalid operation and caused Undefined Behavior")),
                     (None, format!("but due to `-Zmiri-symbolic-alignment-check`, alignment errors can also be false positives")),
                 ],
-            UndefinedBehavior(_) =>
-                vec![
+            UndefinedBehavior(info) => {
+                let mut helps = vec![
                     (None, format!("this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior")),
                     (None, format!("see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information")),
-                ],
+                ];
+                if let UndefinedBehaviorInfo::PointerUseAfterFree(alloc_id, _) = info {
+                    if let Some(span) = ecx.machine.allocated_span(*alloc_id) {
+                        helps.push((Some(span), format!("{:?} was allocated here:", alloc_id)));
+                    }
+                    if let Some(span) = ecx.machine.deallocated_span(*alloc_id) {
+                        helps.push((Some(span), format!("{:?} was deallocated here:", alloc_id)));
+                    }
+                }
+                helps
+            }
             InvalidProgram(
                 InvalidProgramInfo::AlreadyReported(_)
             ) => {

src/machine.rs

@@ -25,7 +25,7 @@ use rustc_middle::{
     },
 };
 use rustc_span::def_id::{CrateNum, DefId};
-use rustc_span::Symbol;
+use rustc_span::{Span, SpanData, Symbol};
 use rustc_target::abi::{Align, Size};
 use rustc_target::spec::abi::Abi;
 
@@ -135,6 +135,17 @@ impl MayLeak for MiriMemoryKind {
     }
 }
 
+impl MiriMemoryKind {
+    /// Whether we have a useful allocation span for an allocation of this kind.
+    fn should_save_allocation_span(self) -> bool {
+        use self::MiriMemoryKind::*;
+        match self {
+            Rust | Miri | C | Mmap => true,
+            Machine | Global | ExternStatic | Tls | WinHeap | Runtime => false,
+        }
+    }
+}
+
 impl fmt::Display for MiriMemoryKind {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use self::MiriMemoryKind::*;
@@ -497,6 +508,10 @@ pub struct MiriMachine<'mir, 'tcx> {
 
     /// Whether to collect a backtrace when each allocation is created, just in case it leaks.
     pub(crate) collect_leak_backtraces: bool,
+
+    /// The spans we will use to report where an allocation was created and deallocated in
+    /// diagnostics.
+    pub(crate) allocation_spans: RefCell<FxHashMap<AllocId, (Option<Span>, Option<Span>)>>,
 }
 
 impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
@@ -621,6 +636,7 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
             stack_addr,
             stack_size,
             collect_leak_backtraces: config.collect_leak_backtraces,
+            allocation_spans: RefCell::new(FxHashMap::default()),
         }
     }
 
@@ -742,6 +758,22 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
     pub(crate) fn page_align(&self) -> Align {
         Align::from_bytes(self.page_size).unwrap()
     }
+
+    pub(crate) fn allocated_span(&self, alloc_id: AllocId) -> Option<SpanData> {
+        self.allocation_spans
+            .borrow()
+            .get(&alloc_id)
+            .and_then(|(allocated, _deallocated)| *allocated)
+            .map(Span::data)
+    }
+
+    pub(crate) fn deallocated_span(&self, alloc_id: AllocId) -> Option<SpanData> {
+        self.allocation_spans
+            .borrow()
+            .get(&alloc_id)
+            .and_then(|(_allocated, deallocated)| *deallocated)
+            .map(Span::data)
+    }
 }
 
 impl VisitTags for MiriMachine<'_, '_> {
@@ -791,6 +823,7 @@ impl VisitTags for MiriMachine<'_, '_> {
             stack_addr: _,
             stack_size: _,
             collect_leak_backtraces: _,
+            allocation_spans: _,
         } = self;
 
         threads.visit_tags(visit);
@@ -1051,6 +1084,16 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for MiriMachine<'mir, 'tcx> {
             },
             |ptr| ecx.global_base_pointer(ptr),
         )?;
+
+        if let MemoryKind::Machine(kind) = kind {
+            if kind.should_save_allocation_span() {
+                ecx.machine
+                    .allocation_spans
+                    .borrow_mut()
+                    .insert(id, (Some(ecx.machine.current_span()), None));
+            }
+        }
+
         Ok(Cow::Owned(alloc))
     }
 
@@ -1181,6 +1224,10 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for MiriMachine<'mir, 'tcx> {
         if let Some(borrow_tracker) = &mut alloc_extra.borrow_tracker {
             borrow_tracker.before_memory_deallocation(alloc_id, prove_extra, range, machine)?;
         }
+        if let Some((_, deallocated_at)) = machine.allocation_spans.borrow_mut().get_mut(&alloc_id)
+        {
+            *deallocated_at = Some(machine.current_span());
+        }
         Ok(())
     }
 

tests/fail/alloc/deallocate-twice.stderr

@@ -6,7 +6,17 @@ LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/deallocate-twice.rs:LL:CC
+   |
+LL |         let x = alloc(Layout::from_size_align_unchecked(1, 1));
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/deallocate-twice.rs:LL:CC
+   |
+LL |         dealloc(x, Layout::from_size_align_unchecked(1, 1));
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: BACKTRACE (of the first span):
    = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
 note: inside `main`
   --> $DIR/deallocate-twice.rs:LL:CC

tests/fail/alloc/reallocate-change-alloc.stderr

@@ -6,7 +6,17 @@ LL |         let _z = *x;
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/reallocate-change-alloc.rs:LL:CC
+   |
+LL |         let x = alloc(Layout::from_size_align_unchecked(1, 1));
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/reallocate-change-alloc.rs:LL:CC
+   |
+LL |         let _y = realloc(x, Layout::from_size_align_unchecked(1, 1), 1);
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: BACKTRACE (of the first span):
    = note: inside `main` at $DIR/reallocate-change-alloc.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

tests/fail/alloc/reallocate-dangling.stderr

@@ -6,7 +6,17 @@ LL |     unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/reallocate-dangling.rs:LL:CC
+   |
+LL |         let x = alloc(Layout::from_size_align_unchecked(1, 1));
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/reallocate-dangling.rs:LL:CC
+   |
+LL |         dealloc(x, Layout::from_size_align_unchecked(1, 1));
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: BACKTRACE (of the first span):
    = note: inside `std::alloc::realloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
 note: inside `main`
   --> $DIR/reallocate-dangling.rs:LL:CC

tests/fail/dangling_pointers/dangling_pointer_addr_of.stderr

@@ -6,7 +6,17 @@ LL |     let x = unsafe { ptr::addr_of!(*p) };
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/dangling_pointer_addr_of.rs:LL:CC
+   |
+LL |         let b = Box::new(42);
+   |                 ^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/dangling_pointer_addr_of.rs:LL:CC
+   |
+LL |     };
+   |     ^
+   = note: BACKTRACE (of the first span):
    = note: inside `main` at RUSTLIB/core/src/ptr/mod.rs:LL:CC
    = note: this error originates in the macro `ptr::addr_of` (in Nightly builds, run with -Z macro-backtrace for more info)
 

tests/fail/dangling_pointers/dangling_pointer_deref.stderr

@@ -6,7 +6,17 @@ LL |     let x = unsafe { *p };
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/dangling_pointer_deref.rs:LL:CC
+   |
+LL |         let b = Box::new(42);
+   |                 ^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/dangling_pointer_deref.rs:LL:CC
+   |
+LL |     };
+   |     ^
+   = note: BACKTRACE (of the first span):
    = note: inside `main` at $DIR/dangling_pointer_deref.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

tests/fail/dangling_pointers/dangling_pointer_offset.stderr

@@ -6,7 +6,17 @@ LL |     let x = unsafe { p.offset(42) };
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/dangling_pointer_offset.rs:LL:CC
+   |
+LL |         let b = Box::new(42);
+   |                 ^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/dangling_pointer_offset.rs:LL:CC
+   |
+LL |     };
+   |     ^
+   = note: BACKTRACE (of the first span):
    = note: inside `main` at $DIR/dangling_pointer_offset.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

tests/fail/dangling_pointers/dangling_pointer_project_underscore.stderr

@@ -6,7 +6,17 @@ LL |         let _ = *p;
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/dangling_pointer_project_underscore.rs:LL:CC
+   |
+LL |         let b = Box::new(42);
+   |                 ^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/dangling_pointer_project_underscore.rs:LL:CC
+   |
+LL |     };
+   |     ^
+   = note: BACKTRACE (of the first span):
    = note: inside `main` at $DIR/dangling_pointer_project_underscore.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

tests/fail/dangling_pointers/dangling_zst_deref.stderr

@@ -6,7 +6,17 @@ LL |     let _x = unsafe { *p };
    |
    = 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:
+help: ALLOC was allocated here:
+  --> $DIR/dangling_zst_deref.rs:LL:CC
+   |
+LL |         let b = Box::new(42);
+   |                 ^^^^^^^^^^^^
+help: ALLOC was deallocated here:
+  --> $DIR/dangling_zst_deref.rs:LL:CC
+   |
+LL |     };
+   |     ^
+   = note: BACKTRACE (of the first span):
    = note: inside `main` at $DIR/dangling_zst_deref.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace