[PATCH v1] rust: bug: pass TAINT_WARN to warn_slowpath_fmt() on UML

[FUJITA Tomonori]

From: FUJITA Tomonori <fujita.tomonori at gmail.com>

On UML, `warn_flags!` calls `warn_slowpath_fmt()` directly. Its third
argument is a taint number, but `warn_on!` passes its bug flags there.

As a result, `add_taint()` gets 2304 instead of 9 (`TAINT_WARN`). The
warning is not recorded: `/proc/sys/kernel/tainted` stays 0 after
`warn_on!` fires, where it should be 512. It also causes an
out-of-bounds write in `add_taint()`.

Pass `TAINT_WARN` directly, as C does on UML.

Cc: stable at vger.kernel.org
Fixes: dff64b072708 ("rust: Add warn_on macro")
Signed-off-by: FUJITA Tomonori <fujita.tomonori at gmail.com>
---
 rust/kernel/bug.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
index 3566f0234ca4..af8eba4563de 100644
--- a/rust/kernel/bug.rs
+++ b/rust/kernel/bug.rs
@@ -85,6 +85,7 @@ macro_rules! warn_flags {
     ($file:expr, $flags:expr) => {
         if false {
             _ = $file;
+            _ = $flags;
         }
 
         // SAFETY: It is always safe to call `warn_slowpath_fmt()`
@@ -93,7 +94,7 @@ macro_rules! warn_flags {
             $crate::bindings::warn_slowpath_fmt(
                 $crate::str::CStrExt::as_char_ptr($crate::c_str!(::core::file!())),
                 line!() as $crate::ffi::c_int,
-                $flags as $crate::ffi::c_uint,
+                $crate::bindings::TAINT_WARN,
                 ::core::ptr::null(),
             );
         }

base-commit: 551c722f40809618230001baccf219193e22fc5a
-- 
2.43.0