[PATCH RFC v2 03/11] rust: miscdevice: fix use after free because missing .owner

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

Currently if miscdevice driver is compiled as module it can cause use
after free when unloading. To reproduce problem with Rust sample driver
we can do:

    tail -f /dev/rust-misc-device
    # And same time as device is open
    sudo rmmod rust_misc_device_module

This will crash system. Fix is to have .owner field filled with module
information. We pass this owner information through vtable.

Reported-by: Youseok Yang <ileixe@gmail.com>
Closes: https://github.com/Rust-for-Linux/linux/issues/1182
Fixes: f893691e7426 ("rust: miscdevice: add base miscdevice abstraction")
Signed-off-by: Kari Argillander <kari.argillander@gmail.com>
---
 rust/kernel/miscdevice.rs        | 5 +++++
 samples/rust/rust_misc_device.rs | 1 +
 2 files changed, 6 insertions(+)

diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
index ba64c8a858f0..d4b0c35c4b60 100644
--- a/rust/kernel/miscdevice.rs
+++ b/rust/kernel/miscdevice.rs
@@ -18,6 +18,7 @@
     mm::virt::VmaNew,
     prelude::*,
     seq_file::SeqFile,
+    this_module::ThisModule,
     types::{ForeignOwnable, Opaque},
 };
 use core::{marker::PhantomData, pin::Pin};
@@ -112,6 +113,9 @@ fn drop(self: Pin<&mut Self>) {
 /// Trait implemented by the private data of an open misc device.
 #[vtable]
 pub trait MiscDevice: Sized {
+    /// Module ownership for this device, provided via `THIS_MODULE`.
+    type ThisModule: ThisModule;
+
     /// What kind of pointer should `Self` be wrapped in.
     type Ptr: ForeignOwnable + Send + Sync;
 
@@ -388,6 +392,7 @@ impl<T: MiscDevice> MiscdeviceVTable<T> {
     }
 
     const VTABLE: bindings::file_operations = bindings::file_operations {
+        owner: T::ThisModule::OWNER.as_ptr(),
         open: Some(Self::open),
         release: Some(Self::release),
         mmap: if T::HAS_MMAP { Some(Self::mmap) } else { None },
diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
index 49dd5814e1ab..464e3026e6e3 100644
--- a/samples/rust/rust_misc_device.rs
+++ b/samples/rust/rust_misc_device.rs
@@ -155,6 +155,7 @@ struct RustMiscDevice {
 
 #[vtable]
 impl MiscDevice for RustMiscDevice {
+    type ThisModule = THIS_MODULE;
     type Ptr = Pin<KBox<Self>>;
 
     fn open(_file: &File, misc: &MiscDeviceRegistration<Self>) -> Result<Pin<KBox<Self>>> {

-- 
2.43.0