Rollup merge of #155817 - folkertdev:link-name-null-empty, r=mejrs

validate `#[link_name = "..."]` & `#[link(name = "...")]` parameters

fixes #155776
fixes #155484

specifically, do not allow NULL bytes and the empty string in `#[link_name = "..."]` and `#[link(name = "...")]`.

Like some of the others I think this formally needs to be looked at by T-lang because these errors would not show up if not linking.

The LLVM erorr on `#[linke_name = "\0"]` is emitted here, it is not e.g. target-specific.

https://github.com/llvm/llvm-project/blob/d593279c0b2891f0b0c8af3f70a1a0383b4ad1b5/llvm/lib/IR/Value.cpp#L336-L342

On `#[link(name = "")]` we already error today. A NULL byte in `#[link(name = "\0")]` is caught by the linker (https://godbolt.org/z/vnz9sYbPs), using `#[link_name = ""]` makes LLVM generate a name (https://godbolt.org/z/1hWEo4cxf) which is not useful and likely to cause linker errors.

r? jdonszelmann

Author: matthiaskrgr

compiler/rustc_attr_parsing/src/attributes/link_attrs.rs

@@ -17,7 +17,7 @@ use crate::session_diagnostics::{
     AsNeededCompatibility, BundleNeedsStatic, EmptyLinkName, ExportSymbolsNeedsStatic,
     ImportNameTypeRaw, ImportNameTypeX86, IncompatibleWasmLink, InvalidLinkModifier,
     InvalidMachoSection, InvalidMachoSectionReason, LinkFrameworkApple, LinkOrdinalOutOfRange,
-    LinkRequiresName, MultipleModifiers, NullOnLinkSection, RawDylibNoNul, RawDylibOnlyWindows,
+    LinkRequiresName, MultipleModifiers, NullOnLinkName, NullOnLinkSection, RawDylibOnlyWindows,
     WholeArchiveNeedsStatic,
 };
 
@@ -42,6 +42,19 @@ impl SingleAttributeParser for LinkNameParser {
             return None;
         };
 
+        if name.as_str().contains('\0') {
+            // `#[link_name = ...]` will be converted to a null-terminated string,
+            // so it may not contain any null characters.
+            cx.emit_err(NullOnLinkName { span: nv.value_span });
+            return None;
+        }
+        if name.is_empty() {
+            // Otherwise LLVM will just make up a name and the linker will fail
+            // to find an empty symbol name.
+            cx.emit_err(EmptyLinkName { span: nv.value_span });
+            return None;
+        }
+
         Some(LinkName { name, span: cx.attr_span })
     }
 }
@@ -218,7 +231,7 @@ impl CombineAttributeParser for LinkParser {
         if wasm_import_module.is_some() {
             (name, kind) = (wasm_import_module, Some(NativeLibKind::WasmImportModule));
         }
-        let Some((name, name_span)) = name else {
+        let Some((name, _name_span)) = name else {
             cx.emit_err(LinkRequiresName { span: cx.attr_span });
             return None;
         };
@@ -230,12 +243,6 @@ impl CombineAttributeParser for LinkParser {
             }
         }
 
-        if let Some(NativeLibKind::RawDylib { .. }) = kind
-            && name.as_str().contains('\0')
-        {
-            cx.emit_err(RawDylibNoNul { span: name_span });
-        }
-
         Some(LinkEntry {
             span: cx.attr_span,
             kind: kind.unwrap_or(NativeLibKind::Unspecified),
@@ -265,9 +272,13 @@ impl LinkParser {
             return false;
         };
 
+        if link_name.as_str().contains('\0') {
+            cx.emit_err(NullOnLinkName { span: nv.value_span });
+        }
         if link_name.is_empty() {
             cx.emit_err(EmptyLinkName { span: nv.value_span });
         }
+
         *name = Some((link_name, nv.value_span));
         true
     }

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -417,6 +417,13 @@ pub(crate) struct NullOnLinkSection {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag("link name may not contain null characters", code = E0648)]
+pub(crate) struct NullOnLinkName {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag("`objc::class!` may not contain null characters")]
 pub(crate) struct NullOnObjcClass {
@@ -991,13 +998,6 @@ pub(crate) struct LinkRequiresName {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag("link name must not contain NUL characters if link kind is `raw-dylib`")]
-pub(crate) struct RawDylibNoNul {
-    #[primary_span]
-    pub span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag("link kind `raw-dylib` is only supported on Windows targets", code = E0455)]
 pub(crate) struct RawDylibOnlyWindows {

tests/ui/attributes/invalid-link-name.rs

@@ -0,0 +1,54 @@
+#![crate_type = "lib"]
+
+#[link(name = "")]
+//~^ ERROR link name must not be empty
+unsafe extern "C" {
+    #[link_name = ""]
+    //~^ ERROR link name must not be empty
+    safe fn empty();
+}
+
+#[link(name = "   ")]
+unsafe extern "C" {
+    #[link_name = "  "]
+    safe fn this_is_fine();
+}
+
+#[export_name = "  "]
+extern "C" fn bar() -> i32 {
+    42
+}
+
+#[link(name = "\0")]
+//~^ ERROR link name may not contain null characters
+unsafe extern "C" {}
+
+#[link(name = "foo\0")]
+//~^ ERROR link name may not contain null characters
+unsafe extern "C" {}
+
+#[link(name = "\0foo")]
+//~^ ERROR link name may not contain null characters
+unsafe extern "C" {}
+
+#[link(name = "fo\0o")]
+//~^ ERROR link name may not contain null characters
+unsafe extern "C" {}
+
+unsafe extern "C" {
+    #[link_name = "\0"]
+    //~^ ERROR link name may not contain null characters
+    safe fn empty_null();
+
+    #[link_name = "foo\0"]
+    //~^ ERROR link name may not contain null characters
+    safe fn trailing_null();
+
+    #[link_name = "\0foo"]
+    //~^ ERROR link name may not contain null characters
+    safe fn leading_null();
+
+    #[link_name = "fo\0o"]
+    //~^ ERROR link name may not contain null characters
+    safe fn middle_null();
+}

tests/ui/attributes/invalid-link-name.stderr

@@ -0,0 +1,64 @@
+error[E0454]: link name must not be empty
+  --> $DIR/invalid-link-name.rs:3:15
+   |
+LL | #[link(name = "")]
+   |               ^^ empty link name
+
+error[E0454]: link name must not be empty
+  --> $DIR/invalid-link-name.rs:6:19
+   |
+LL |     #[link_name = ""]
+   |                   ^^ empty link name
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:22:15
+   |
+LL | #[link(name = "\0")]
+   |               ^^^^
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:26:15
+   |
+LL | #[link(name = "foo\0")]
+   |               ^^^^^^^
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:30:15
+   |
+LL | #[link(name = "\0foo")]
+   |               ^^^^^^^
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:34:15
+   |
+LL | #[link(name = "fo\0o")]
+   |               ^^^^^^^
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:39:19
+   |
+LL |     #[link_name = "\0"]
+   |                   ^^^^
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:43:19
+   |
+LL |     #[link_name = "foo\0"]
+   |                   ^^^^^^^
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:47:19
+   |
+LL |     #[link_name = "\0foo"]
+   |                   ^^^^^^^
+
+error[E0648]: link name may not contain null characters
+  --> $DIR/invalid-link-name.rs:51:19
+   |
+LL |     #[link_name = "fo\0o"]
+   |                   ^^^^^^^
+
+error: aborting due to 10 previous errors
+
+Some errors have detailed explanations: E0454, E0648.
+For more information about an error, try `rustc --explain E0454`.

tests/ui/linkage-attr/raw-dylib/elf/malformed-link-name.rs

@@ -11,10 +11,8 @@ unsafe extern "C" {
     pub safe fn exit_0(status: i32) -> !; //~ ERROR link name must be well-formed if link kind is `raw-dylib`
     #[link_name = "@GLIBC_2.2.5"]
     pub safe fn exit_1(status: i32) -> !; //~ ERROR link name must be well-formed if link kind is `raw-dylib`
-    #[link_name = "ex\0it@GLIBC_2.2.5"]
-    pub safe fn exit_2(status: i32) -> !; //~ ERROR link name must be well-formed if link kind is `raw-dylib`
     #[link_name = "exit@@GLIBC_2.2.5"]
-    pub safe fn exit_3(status: i32) -> !; //~ ERROR link name must be well-formed if link kind is `raw-dylib`
+    pub safe fn exit_2(status: i32) -> !; //~ ERROR link name must be well-formed if link kind is `raw-dylib`
 }
 
 fn main() {}

tests/ui/linkage-attr/raw-dylib/elf/malformed-link-name.stderr

@@ -16,11 +16,5 @@ error: link name must be well-formed if link kind is `raw-dylib`
 LL |     pub safe fn exit_2(status: i32) -> !;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: link name must be well-formed if link kind is `raw-dylib`
-  --> $DIR/malformed-link-name.rs:17:5
-   |
-LL |     pub safe fn exit_3(status: i32) -> !;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors