[PATCH RFC v2 04/11] rust: block: fix missing owner field in block_device_operations

[Kari Argillander <kari.argillander@gmail.com>]

Kernel has now enabled "const_refs_to_static" feature. We can fix TODO
item now. Fix this by defining owner in vtable so we can read it from
there.  As this table needs to be const we need to define it in
operations so we do not need pass THIS_MODULE alongside with
GenDiskBuilder::build().

This will probably fix some use after free.

Fixes: 3253aba3408a ("rust: block: introduce `kernel::block::mq` module")
Signed-off-by: Kari Argillander <kari.argillander@gmail.com>
---
 drivers/block/rnull/rnull.rs       |  1 +
 rust/kernel/block/mq.rs            |  1 +
 rust/kernel/block/mq/gen_disk.rs   | 30 ++++--------------------------
 rust/kernel/block/mq/operations.rs | 30 ++++++++++++++++++++++++++++++
 4 files changed, 36 insertions(+), 26 deletions(-)

diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index a9d5e575a2c4..862369ab9b5c 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -74,6 +74,7 @@ struct QueueData {
 
 #[vtable]
 impl Operations for NullBlkDevice {
+    type ThisModule = THIS_MODULE;
     type QueueData = KBox<QueueData>;
 
     #[inline(always)]
diff --git a/rust/kernel/block/mq.rs b/rust/kernel/block/mq.rs
index 1fd0d54dd549..0c8e9e316952 100644
--- a/rust/kernel/block/mq.rs
+++ b/rust/kernel/block/mq.rs
@@ -68,6 +68,7 @@
 //!
 //! #[vtable]
 //! impl Operations for MyBlkDevice {
+//!     type ThisModule = THIS_MODULE;
 //!     type QueueData = ();
 //!
 //!     fn queue_rq(_queue_data: (), rq: ARef<Request<Self>>, _is_last: bool) -> Result {
diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
index 1ce815c8cdab..4d5d378577ec 100644
--- a/rust/kernel/block/mq/gen_disk.rs
+++ b/rust/kernel/block/mq/gen_disk.rs
@@ -7,7 +7,7 @@
 
 use crate::{
     bindings,
-    block::mq::{Operations, TagSet},
+    block::mq::{operations::OperationsVTable, Operations, TagSet},
     error::{self, from_err_ptr, Result},
     fmt::{self, Write},
     prelude::*,
@@ -126,32 +126,10 @@ pub fn build<T: Operations>(
             )
         })?;
 
-        const TABLE: bindings::block_device_operations = bindings::block_device_operations {
-            submit_bio: None,
-            open: None,
-            release: None,
-            ioctl: None,
-            compat_ioctl: None,
-            check_events: None,
-            unlock_native_capacity: None,
-            getgeo: None,
-            set_read_only: None,
-            swap_slot_free_notify: None,
-            report_zones: None,
-            devnode: None,
-            alternative_gpt_sector: None,
-            get_unique_id: None,
-            // TODO: Set to THIS_MODULE. Waiting for const_refs_to_static feature to
-            // be merged (unstable in rustc 1.78 which is staged for linux 6.10)
-            // <https://github.com/rust-lang/rust/issues/119618>
-            owner: core::ptr::null_mut(),
-            pr_ops: core::ptr::null_mut(),
-            free_disk: None,
-            poll_bio: None,
-        };
-
         // SAFETY: `gendisk` is a valid pointer as we initialized it above
-        unsafe { (*gendisk).fops = &TABLE };
+        unsafe {
+            (*gendisk).fops = OperationsVTable::<T>::build_block_device_operations();
+        }
 
         let mut writer = NullTerminatedFormatter::new(
             // SAFETY: `gendisk` points to a valid and initialized instance. We
diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs
index 8ad46129a52c..0f8f616590fb 100644
--- a/rust/kernel/block/mq/operations.rs
+++ b/rust/kernel/block/mq/operations.rs
@@ -10,6 +10,7 @@
     error::{from_result, Result},
     prelude::*,
     sync::{aref::ARef, Refcount},
+    this_module::ThisModule,
     types::ForeignOwnable,
 };
 use core::marker::PhantomData;
@@ -28,6 +29,9 @@
 /// [module level documentation]: kernel::block::mq
 #[macros::vtable]
 pub trait Operations: Sized {
+    /// Module ownership for this device, provided via `THIS_MODULE`.
+    type ThisModule: ThisModule;
+
     /// Data associated with the `struct request_queue` that is allocated for
     /// the `GenDisk` associated with this `Operations` implementation.
     type QueueData: ForeignOwnable;
@@ -280,7 +284,33 @@ impl<T: Operations> OperationsVTable<T> {
         show_rq: None,
     };
 
+    const BLOCK_OPS: bindings::block_device_operations = bindings::block_device_operations {
+        submit_bio: None,
+        open: None,
+        release: None,
+        ioctl: None,
+        compat_ioctl: None,
+        check_events: None,
+        unlock_native_capacity: None,
+        getgeo: None,
+        set_read_only: None,
+        swap_slot_free_notify: None,
+        report_zones: None,
+        devnode: None,
+        alternative_gpt_sector: None,
+        get_unique_id: None,
+        owner: T::ThisModule::OWNER.as_ptr(),
+        pr_ops: core::ptr::null_mut(),
+        free_disk: None,
+        poll_bio: None,
+    };
+
     pub(crate) const fn build() -> &'static bindings::blk_mq_ops {
         &Self::VTABLE
     }
+
+    pub(crate) const fn build_block_device_operations() -> &'static bindings::block_device_operations
+    {
+        &Self::BLOCK_OPS
+    }
 }

-- 
2.43.0