validate link name parameter

specifically, do not allow NULL bytes and the empty string

Author: folkertdev

compiler/rustc_attr_parsing/src/attributes/link_attrs.rs

@@ -17,8 +17,8 @@ use crate::session_diagnostics::{
     AsNeededCompatibility, BundleNeedsStatic, EmptyLinkName, ExportSymbolsNeedsStatic,
     ImportNameTypeRaw, ImportNameTypeX86, IncompatibleWasmLink, InvalidLinkModifier,
     InvalidMachoSection, InvalidMachoSectionReason, LinkFrameworkApple, LinkOrdinalOutOfRange,
-    LinkRequiresName, MultipleModifiers, NullOnLinkSection, RawDylibNoNul, RawDylibOnlyWindows,
-    WholeArchiveNeedsStatic,
+    LinkRequiresName, MultipleModifiers, NullOnLinkName, NullOnLinkSection, RawDylibNoNul,
+    RawDylibOnlyWindows, WholeArchiveNeedsStatic,
 };
 
 pub(crate) struct LinkNameParser;
@@ -46,6 +46,19 @@ impl<S: Stage> SingleAttributeParser<S> 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 })
     }
 }
@@ -270,9 +283,13 @@ 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

@@ -410,6 +410,13 @@ 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 {

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