Merge tag 'rust-fixes-6.2' of https://github.com/Rust-for-Linux/linux

Pull rust fix from Miguel Ojeda:

 - Avoid evaluating arguments in 'pr_*' macros in 'unsafe' blocks

* tag 'rust-fixes-6.2' of https://github.com/Rust-for-Linux/linux:
  rust: print: avoid evaluating arguments in `pr_*` macros in `unsafe` blocks

rust/kernel/print.rs

@@ -142,18 +142,25 @@ pub fn call_printk_cont(args: fmt::Arguments<'_>) {
 macro_rules! print_macro (
     // The non-continuation cases (most of them, e.g. `INFO`).
     ($format_string:path, false, $($arg:tt)+) => (
+        // To remain sound, `arg`s must be expanded outside the `unsafe` block.
+        // Typically one would use a `let` binding for that; however, `format_args!`
+        // takes borrows on the arguments, but does not extend the scope of temporaries.
+        // Therefore, a `match` expression is used to keep them around, since
+        // the scrutinee is kept until the end of the `match`.
+        match format_args!($($arg)+) {
             // SAFETY: This hidden macro should only be called by the documented
             // printing macros which ensure the format string is one of the fixed
             // ones. All `__LOG_PREFIX`s are null-terminated as they are generated
             // by the `module!` proc macro or fixed values defined in a kernel
             // crate.
-        unsafe {
+            args => unsafe {
                 $crate::print::call_printk(
                     &$format_string,
                     crate::__LOG_PREFIX,
-                format_args!($($arg)+),
+                    args,
                 );
             }
+        }
     );
 
     // The `CONT` case.