* [PATCH] cred: clarify usage of get_cred_rcu()
From: Alice Ryhl @ 2026-02-20 9:19 UTC (permalink / raw)
To: Paul Moore, Serge Hallyn; +Cc: linux-security-module, linux-kernel, Alice Ryhl
After being confused by looking at get_cred() and get_cred_rcu(), I
figured out what's going on. Thus, add some comments to clarify how
get_cred_rcu() works for the benefit of others looking in the future.
Note that in principle we could add an assertion that non_rcu is zero in
the failure path of atomic_long_inc_not_zero().
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
include/linux/cred.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/include/linux/cred.h b/include/linux/cred.h
index ed1609d78cd7..95dcf5e967c7 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -213,32 +213,50 @@ * get_cred_many - Get references on a set of credentials
static inline const struct cred *get_cred_many(const struct cred *cred, int nr)
{
struct cred *nonconst_cred = (struct cred *) cred;
if (!cred)
return cred;
nonconst_cred->non_rcu = 0;
atomic_long_add(nr, &nonconst_cred->usage);
return cred;
}
/*
* get_cred - Get a reference on a set of credentials
* @cred: The credentials to reference
*
* Get a reference on the specified set of credentials. The caller must
* release the reference. If %NULL is passed, it is returned with no action.
*
* This is used to deal with a committed set of credentials.
*/
static inline const struct cred *get_cred(const struct cred *cred)
{
return get_cred_many(cred, 1);
}
+/*
+ * get_cred_rcu - Get a reference on a set of credentials under rcu
+ * @cred: The credentials to reference
+ *
+ * Get a reference on the specified set of credentials, or %NULL if the last
+ * refcount has already been put.
+ *
+ * This is used to obtain a reference under an rcu read lock.
+ */
static inline const struct cred *get_cred_rcu(const struct cred *cred)
{
struct cred *nonconst_cred = (struct cred *) cred;
if (!cred)
return NULL;
if (!atomic_long_inc_not_zero(&nonconst_cred->usage))
return NULL;
+ /*
+ * If non_rcu is not already zero, then this call to get_cred_rcu() is
+ * probably wrong because if 'usage' goes to zero prior to this call,
+ * then get_cred_rcu() assumes it is freed with rcu.
+ *
+ * However, an exception to this is using get_cred_rcu() in cases where
+ * get_cred() would have been okay. To support that case, we do not
+ * check non_rcu and set it to zero regardless.
+ */
nonconst_cred->non_rcu = 0;
return cred;
}
--
2.53.0.345.g96ddfc5eaa-goog
^ permalink raw reply related
* [PATCH v15 4/9] rust: aref: update formatting of use statements
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
Update formatting if use statements in preparation for next commit.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/sync/aref.rs | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index efe16a7fdfa5d..3c63c9a5fb9be 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -17,7 +17,12 @@
//! [`Arc`]: crate::sync::Arc
//! [`Arc<T>`]: crate::sync::Arc
-use core::{marker::PhantomData, mem::ManuallyDrop, ops::Deref, ptr::NonNull};
+use core::{
+ marker::PhantomData,
+ mem::ManuallyDrop,
+ ops::Deref,
+ ptr::NonNull, //
+};
/// Types that are internally reference counted.
///
--
2.51.2
^ permalink raw reply related
* [PATCH v15 8/9] rust: implement `ForeignOwnable` for `Owned`
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
Implement `ForeignOwnable` for `Owned<T>`. This allows use of `Owned<T>` in
places such as the `XArray`.
Note that `T` does not need to implement `ForeignOwnable` for `Owned<T>` to
implement `ForeignOwnable`.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/owned.rs | 45 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 44 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index a9bc871e07ce1..b115b4f3db6d0 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -16,7 +16,10 @@
};
use kernel::{
sync::aref::ARef,
- types::RefCounted, //
+ types::{
+ ForeignOwnable, //
+ RefCounted,
+ }, //
};
/// Types that specify their own way of performing allocation and destruction. Typically, this trait
@@ -120,6 +123,7 @@ pub unsafe trait Ownable {
///
/// - The [`Owned<T>`] has exclusive access to the instance of `T`.
/// - The instance of `T` will stay alive at least as long as the [`Owned<T>`] is alive.
+#[repr(transparent)]
pub struct Owned<T: Ownable> {
ptr: NonNull<T>,
}
@@ -201,6 +205,45 @@ fn drop(&mut self) {
}
}
+// SAFETY: We derive the pointer to `T` from a valid `T`, so the returned
+// pointer satisfy alignment requirements of `T`.
+unsafe impl<T: Ownable + 'static> ForeignOwnable for Owned<T> {
+ const FOREIGN_ALIGN: usize = core::mem::align_of::<Owned<T>>();
+
+ type Borrowed<'a> = &'a T;
+ type BorrowedMut<'a> = Pin<&'a mut T>;
+
+ fn into_foreign(self) -> *mut kernel::ffi::c_void {
+ let ptr = self.ptr.as_ptr().cast();
+ core::mem::forget(self);
+ ptr
+ }
+
+ unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self {
+ Self {
+ // SAFETY: By function safety contract, `ptr` came from
+ // `into_foreign` and cannot be null.
+ ptr: unsafe { NonNull::new_unchecked(ptr.cast()) },
+ }
+ }
+
+ unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowed<'a> {
+ // SAFETY: By function safety requirements, `ptr` is valid for use as a
+ // reference for `'a`.
+ unsafe { &*ptr.cast() }
+ }
+
+ unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a> {
+ // SAFETY: By function safety requirements, `ptr` is valid for use as a
+ // unique reference for `'a`.
+ let inner = unsafe { &mut *ptr.cast() };
+
+ // SAFETY: We never move out of inner, and we do not hand out mutable
+ // references when `T: !Unpin`.
+ unsafe { Pin::new_unchecked(inner) }
+ }
+}
+
/// A trait for objects that can be wrapped in either one of the reference types [`Owned`] and
/// [`ARef`].
///
--
2.51.2
^ permalink raw reply related
* [PATCH v15 1/9] rust: types: Add Ownable/Owned types
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg, Asahi Lina, Oliver Mangold
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
From: Asahi Lina <lina+kernel@asahilina.net>
By analogy to `AlwaysRefCounted` and `ARef`, an `Ownable` type is a
(typically C FFI) type that *may* be owned by Rust, but need not be. Unlike
`AlwaysRefCounted`, this mechanism expects the reference to be unique
within Rust, and does not allow cloning.
Conceptually, this is similar to a `KBox<T>`, except that it delegates
resource management to the `T` instead of using a generic allocator.
[ om:
- Split code into separate file and `pub use` it from types.rs.
- Make from_raw() and into_raw() public.
- Remove OwnableMut, and make DerefMut dependent on Unpin instead.
- Usage example/doctest for Ownable/Owned.
- Fixes to documentation and commit message.
]
Link: https://lore.kernel.org/all/20250202-rust-page-v1-1-e3170d7fe55e@asahilina.net/
Signed-off-by: Asahi Lina <lina+kernel@asahilina.net>
Co-developed-by: Oliver Mangold <oliver.mangold@pm.me>
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
[ Andreas: Updated documentation, examples, and formatting ]
Reviewed-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/lib.rs | 1 +
rust/kernel/owned.rs | 196 +++++++++++++++++++++++++++++++++++++++++++++++
rust/kernel/sync/aref.rs | 5 ++
rust/kernel/types.rs | 11 ++-
4 files changed, 212 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 696f62f85eb5f..a2bec807f03f1 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -121,6 +121,7 @@
pub mod of;
#[cfg(CONFIG_PM_OPP)]
pub mod opp;
+pub mod owned;
pub mod page;
#[cfg(CONFIG_PCI)]
pub mod pci;
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
new file mode 100644
index 0000000000000..d566ad0aa1c99
--- /dev/null
+++ b/rust/kernel/owned.rs
@@ -0,0 +1,196 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Unique owned pointer types for objects with custom drop logic.
+//!
+//! These pointer types are useful for C-allocated objects which by API-contract
+//! are owned by Rust, but need to be freed through the C API.
+
+use core::{
+ mem::ManuallyDrop,
+ ops::{
+ Deref,
+ DerefMut, //
+ },
+ pin::Pin,
+ ptr::NonNull, //
+};
+
+/// Types that specify their own way of performing allocation and destruction. Typically, this trait
+/// is implemented on types from the C side.
+///
+/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type. This
+/// is useful when it is desirable to tie the lifetime of the reference to an owned object, rather
+/// than pass around a bare reference. [`Ownable`] types can define custom drop logic that is
+/// executed when the owned reference [`Owned<Self>`] pointing to the object is dropped.
+///
+/// Note: The underlying object is not required to provide internal reference counting, because it
+/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
+/// [`AlwaysRefCounted`](crate::types::AlwaysRefCounted) should be implemented.
+///
+/// # Safety
+///
+/// Implementers must ensure that the [`release()`](Self::release) function frees the underlying
+/// object in the correct way for a valid, owned object of this type.
+///
+/// # Examples
+///
+/// A minimal example implementation of [`Ownable`] and its usage with [`Owned`] looks like
+/// this:
+///
+/// ```
+/// # #![expect(clippy::disallowed_names)]
+/// # use core::cell::Cell;
+/// # use core::ptr::NonNull;
+/// # use kernel::sync::global_lock;
+/// # use kernel::alloc::{flags, kbox::KBox, AllocError};
+/// # use kernel::types::{Owned, Ownable};
+///
+/// // Let's count the allocations to see if freeing works.
+/// kernel::sync::global_lock! {
+/// // SAFETY: we call `init()` right below, before doing anything else.
+/// unsafe(uninit) static FOO_ALLOC_COUNT: Mutex<usize> = 0;
+/// }
+/// // SAFETY: We call `init()` only once, here.
+/// unsafe { FOO_ALLOC_COUNT.init() };
+///
+/// struct Foo;
+///
+/// impl Foo {
+/// fn new() -> Result<Owned<Self>> {
+/// // We are just using a `KBox` here to handle the actual allocation, as our `Foo` is
+/// // not actually a C-allocated object.
+/// let result = KBox::new(
+/// Foo {},
+/// flags::GFP_KERNEL,
+/// )?;
+/// let result = NonNull::new(KBox::into_raw(result))
+/// .expect("Raw pointer to newly allocation KBox is null, this should never happen.");
+/// // Count new allocation
+/// *FOO_ALLOC_COUNT.lock() += 1;
+/// // SAFETY: We just allocated the `Self`, thus it is valid and there cannot be any other
+/// // Rust references. Calling `into_raw()` makes us responsible for ownership and we won't
+/// // use the raw pointer anymore. Thus we can transfer ownership to the `Owned`.
+/// Ok(unsafe { Owned::from_raw(result) })
+/// }
+/// }
+///
+/// // SAFETY: The implementation of `release` in this trait implementation correctly frees the
+/// // owned `Foo`.
+/// unsafe impl Ownable for Foo {
+/// unsafe fn release(this: NonNull<Self>) {
+/// // SAFETY: The [`KBox<Self>`] is still alive. We can pass ownership to the [`KBox`], as
+/// // by requirement on calling this function, the `Self` will no longer be used by the
+/// // caller.
+/// drop(unsafe { KBox::from_raw(this.as_ptr()) });
+/// // Count released allocation
+/// *FOO_ALLOC_COUNT.lock() -= 1;
+/// }
+/// }
+///
+/// {
+/// let foo = Foo::new().expect("Failed to allocate a Foo. This shouldn't happen");
+/// assert!(*FOO_ALLOC_COUNT.lock() == 1);
+/// }
+/// // `foo` is out of scope now, so we expect no live allocations.
+/// assert!(*FOO_ALLOC_COUNT.lock() == 0);
+/// ```
+pub unsafe trait Ownable {
+ /// Releases the object.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that:
+ /// - `this` points to a valid `Self`.
+ /// - `*this` is no longer used after this call.
+ unsafe fn release(this: NonNull<Self>);
+}
+
+/// A mutable reference to an owned `T`.
+///
+/// The [`Ownable`] is automatically freed or released when an instance of [`Owned`] is
+/// dropped.
+///
+/// # Invariants
+///
+/// - The [`Owned<T>`] has exclusive access to the instance of `T`.
+/// - The instance of `T` will stay alive at least as long as the [`Owned<T>`] is alive.
+pub struct Owned<T: Ownable> {
+ ptr: NonNull<T>,
+}
+
+impl<T: Ownable> Owned<T> {
+ /// Creates a new instance of [`Owned`].
+ ///
+ /// This function takes over ownership of the underlying object.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that:
+ /// - `ptr` points to a valid instance of `T`.
+ /// - Ownership of the underlying `T` can be transferred to the `Self<T>` (i.e. operations
+ /// which require ownership will be safe).
+ /// - An `Owned<T>` is a mutable reference to the underlying object. As such,
+ /// the object must not be accessed (read or mutated) through any pointer
+ /// other than the created `Owned<T>`. Opt-out is still possible similar to
+ /// a mutable reference (e.g. by using [`Opaque`]).
+ ///
+ /// [`Opaque`]: kernel::types::Opaque
+ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
+ // INVARIANT: By function safety requirement:
+ // - The resulting object has exclusive access to the `T` pointed to by `ptr`.
+ // - The `T` object pointed to by `ptr` is alive at least as long as the returned `Self`.
+ Self { ptr }
+ }
+
+ /// Consumes the [`Owned`], returning a raw pointer.
+ ///
+ /// This function does not drop the underlying `T`. When this function returns, ownership of the
+ /// underlying `T` is with the caller.
+ pub fn into_raw(me: Self) -> NonNull<T> {
+ ManuallyDrop::new(me).ptr
+ }
+
+ /// Get a pinned mutable reference to the data owned by this `Owned<T>`.
+ pub fn as_pin_mut(&mut self) -> Pin<&mut T> {
+ // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
+ // return a mutable reference to it.
+ let unpinned = unsafe { self.ptr.as_mut() };
+
+ // SAFETY: We never hand out unpinned mutable references to the data in
+ // `Self`, unless the contained type is `Unpin`.
+ unsafe { Pin::new_unchecked(unpinned) }
+ }
+}
+
+// SAFETY: It is safe to send an [`Owned<T>`] to another thread when the underlying `T` is [`Send`],
+// because of the ownership invariant. Sending an [`Owned<T>`] is equivalent to sending the `T`.
+unsafe impl<T: Ownable + Send> Send for Owned<T> {}
+
+// SAFETY: It is safe to send [`&Owned<T>`] to another thread when the underlying `T` is [`Sync`],
+// because of the ownership invariant. Sending an [`&Owned<T>`] is equivalent to sending the `&T`.
+unsafe impl<T: Ownable + Sync> Sync for Owned<T> {}
+
+impl<T: Ownable> Deref for Owned<T> {
+ type Target = T;
+
+ fn deref(&self) -> &Self::Target {
+ // SAFETY: The type invariants guarantee that the object is valid.
+ unsafe { self.ptr.as_ref() }
+ }
+}
+
+impl<T: Ownable + Unpin> DerefMut for Owned<T> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
+ // return a mutable reference to it.
+ unsafe { self.ptr.as_mut() }
+ }
+}
+
+impl<T: Ownable> Drop for Owned<T> {
+ fn drop(&mut self) {
+ // SAFETY: The type invariants guarantee that the `Owned` owns the object we're about to
+ // release.
+ unsafe { T::release(self.ptr) };
+ }
+}
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index 0d24a0432015d..e175aefe86151 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -29,6 +29,11 @@
/// Rust code, the recommendation is to use [`Arc`](crate::sync::Arc) to create reference-counted
/// instances of a type.
///
+/// Note: Implementing this trait allows types to be wrapped in an [`ARef<Self>`]. It requires an
+/// internal reference count and provides only shared references. If unique references are required
+/// [`Ownable`](crate::types::Ownable) should be implemented which allows types to be wrapped in an
+/// [`Owned<Self>`](crate::types::Owned).
+///
/// # Safety
///
/// Implementers must ensure that increments to the reference count keep the object alive in memory
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 9c5e7dbf16323..4aec7b699269a 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -11,7 +11,16 @@
};
use pin_init::{PinInit, Wrapper, Zeroable};
-pub use crate::sync::aref::{ARef, AlwaysRefCounted};
+pub use crate::{
+ owned::{
+ Ownable,
+ Owned, //
+ },
+ sync::aref::{
+ ARef,
+ AlwaysRefCounted, //
+ }, //
+};
/// Used to transfer ownership to and from foreign (non-Rust) languages.
///
--
2.51.2
^ permalink raw reply related
* [PATCH v15 7/9] rust: page: convert to `Ownable`
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg, Asahi Lina, Asahi Lina
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
From: Asahi Lina <lina+kernel@asahilina.net>
This allows Page references to be returned as borrowed references,
without necessarily owning the struct page.
Signed-off-by: Asahi Lina <lina@asahilina.net>
[ Andreas: Fix formatting and add a safety comment. ]
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/page.rs | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index bf3bed7e2d3fe..4591b7b01c3d2 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -10,6 +10,11 @@
bindings,
error::code::*,
error::Result,
+ types::{
+ Opaque,
+ Ownable,
+ Owned, //
+ },
uaccess::UserSliceReader, //
};
use core::{
@@ -83,7 +88,7 @@ pub const fn page_align(addr: usize) -> usize {
///
/// [`VBox`]: kernel::alloc::VBox
/// [`Vmalloc`]: kernel::alloc::allocator::Vmalloc
-pub struct BorrowedPage<'a>(ManuallyDrop<Page>, PhantomData<&'a Page>);
+pub struct BorrowedPage<'a>(ManuallyDrop<Owned<Page>>, PhantomData<&'a Owned<Page>>);
impl<'a> BorrowedPage<'a> {
/// Constructs a [`BorrowedPage`] from a raw pointer to a `struct page`.
@@ -93,7 +98,9 @@ impl<'a> BorrowedPage<'a> {
/// - `ptr` must point to a valid `bindings::page`.
/// - `ptr` must remain valid for the entire lifetime `'a`.
pub unsafe fn from_raw(ptr: NonNull<bindings::page>) -> Self {
- let page = Page { page: ptr };
+ let page: Owned<Page> =
+ // SAFETY: By function safety requirements `ptr` is non null and valid for 'a.
+ unsafe { Owned::from_raw(NonNull::new_unchecked(ptr.as_ptr().cast())) };
// INVARIANT: The safety requirements guarantee that `ptr` is valid for the entire lifetime
// `'a`.
@@ -126,8 +133,9 @@ pub trait AsPageIter {
/// # Invariants
///
/// The pointer is valid, and has ownership over the page.
+#[repr(transparent)]
pub struct Page {
- page: NonNull<bindings::page>,
+ page: Opaque<bindings::page>,
}
// SAFETY: Pages have no logic that relies on them staying on a given thread, so moving them across
@@ -161,19 +169,20 @@ impl Page {
/// # Ok::<(), kernel::alloc::AllocError>(())
/// ```
#[inline]
- pub fn alloc_page(flags: Flags) -> Result<Self, AllocError> {
+ pub fn alloc_page(flags: Flags) -> Result<Owned<Self>, AllocError> {
// SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
// is always safe to call this method.
let page = unsafe { bindings::alloc_pages(flags.as_raw(), 0) };
let page = NonNull::new(page).ok_or(AllocError)?;
- // INVARIANT: We just successfully allocated a page, so we now have ownership of the newly
- // allocated page. We transfer that ownership to the new `Page` object.
- Ok(Self { page })
+ // SAFETY: We just successfully allocated a page, so we now have ownership of the newly
+ // allocated page. We transfer that ownership to the new `Owned<Page>` object.
+ // Since `Page` is transparent, we can cast the pointer directly.
+ Ok(unsafe { Owned::from_raw(page.cast()) })
}
/// Returns a raw pointer to the page.
pub fn as_ptr(&self) -> *mut bindings::page {
- self.page.as_ptr()
+ Opaque::cast_into(&self.page)
}
/// Get the node id containing this page.
@@ -348,10 +357,13 @@ pub unsafe fn copy_from_user_slice_raw(
}
}
-impl Drop for Page {
+// SAFETY: `Owned<Page>` objects returned by Page::alloc_page() follow the requirements of
+// the Ownable abstraction.
+unsafe impl Ownable for Page {
#[inline]
- fn drop(&mut self) {
+ unsafe fn release(this: NonNull<Self>) {
// SAFETY: By the type invariants, we have ownership of the page and can free it.
- unsafe { bindings::__free_pages(self.page.as_ptr(), 0) };
+ // Since Page is transparent, we can cast the raw pointer directly.
+ unsafe { bindings::__free_pages(this.cast().as_ptr(), 0) };
}
}
--
2.51.2
^ permalink raw reply related
* [PATCH v15 5/9] rust: Add `OwnableRefCounted`
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg, Oliver Mangold
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
From: Oliver Mangold <oliver.mangold@pm.me>
Types implementing one of these traits can safely convert between an
`ARef<T>` and an `Owned<T>`.
This is useful for types which generally are accessed through an `ARef`
but have methods which can only safely be called when the reference is
unique, like e.g. `block::mq::Request::end_ok()`.
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
[ Andreas: Fix formatting, update documentation, fix error handling in
examples. ]
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/owned.rs | 143 ++++++++++++++++++++++++++++++++++++++++++++---
rust/kernel/sync/aref.rs | 15 ++++-
rust/kernel/types.rs | 1 +
3 files changed, 150 insertions(+), 9 deletions(-)
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index b8d3b9c725cf6..a9bc871e07ce1 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -14,18 +14,24 @@
pin::Pin,
ptr::NonNull, //
};
+use kernel::{
+ sync::aref::ARef,
+ types::RefCounted, //
+};
/// Types that specify their own way of performing allocation and destruction. Typically, this trait
/// is implemented on types from the C side.
///
-/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type. This
-/// is useful when it is desirable to tie the lifetime of the reference to an owned object, rather
-/// than pass around a bare reference. [`Ownable`] types can define custom drop logic that is
-/// executed when the owned reference [`Owned<Self>`] pointing to the object is dropped.
+/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type.
+/// - This is useful when it is desirable to tie the lifetime of an object reference to an owned
+/// object, rather than pass around a bare reference.
+/// - [`Ownable`] types can define custom drop logic that is executed when the owned reference
+/// of type [`Owned<_>`] pointing to the object is dropped.
///
/// Note: The underlying object is not required to provide internal reference counting, because it
/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
-/// [`RefCounted`](crate::types::RefCounted) should be implemented.
+/// [`RefCounted`] should be implemented. [`OwnableRefCounted`] should be implemented if conversion
+/// between unique and shared (reference counted) ownership is needed.
///
/// # Safety
///
@@ -63,8 +69,7 @@
/// Foo {},
/// flags::GFP_KERNEL,
/// )?;
-/// let result = NonNull::new(KBox::into_raw(result))
-/// .expect("Raw pointer to newly allocation KBox is null, this should never happen.");
+/// let result = NonNull::new(KBox::into_raw(result)).ok_or(ENOMEM)?;
/// // Count new allocation
/// *FOO_ALLOC_COUNT.lock() += 1;
/// // SAFETY: We just allocated the `Self`, thus it is valid and there cannot be any other
@@ -88,11 +93,12 @@
/// }
///
/// {
-/// let foo = Foo::new().expect("Failed to allocate a Foo. This shouldn't happen");
+/// let foo = Foo::new()?;
/// assert!(*FOO_ALLOC_COUNT.lock() == 1);
/// }
/// // `foo` is out of scope now, so we expect no live allocations.
/// assert!(*FOO_ALLOC_COUNT.lock() == 0);
+/// # Ok::<(), Error>(())
/// ```
pub unsafe trait Ownable {
/// Releases the object.
@@ -194,3 +200,124 @@ fn drop(&mut self) {
unsafe { T::release(self.ptr) };
}
}
+
+/// A trait for objects that can be wrapped in either one of the reference types [`Owned`] and
+/// [`ARef`].
+///
+/// # Examples
+///
+/// A minimal example implementation of [`OwnableRefCounted`], [`Ownable`] and its usage with
+/// [`ARef`] and [`Owned`] looks like this:
+///
+/// ```
+/// # #![expect(clippy::disallowed_names)]
+/// # use core::cell::Cell;
+/// # use core::ptr::NonNull;
+/// # use kernel::alloc::{flags, kbox::KBox, AllocError};
+/// # use kernel::sync::aref::{ARef, RefCounted};
+/// # use kernel::types::{Owned, Ownable, OwnableRefCounted};
+///
+/// // An internally refcounted struct for demonstration purposes.
+/// //
+/// // # Invariants
+/// //
+/// // - `refcount` is always non-zero for a valid object.
+/// // - `refcount` is >1 if there is more than one Rust reference to it.
+/// //
+/// struct Foo {
+/// refcount: Cell<usize>,
+/// }
+///
+/// impl Foo {
+/// fn new() -> Result<Owned<Self>> {
+/// // We are just using a `KBox` here to handle the actual allocation, as our `Foo` is
+/// // not actually a C-allocated object.
+/// let result = KBox::new(
+/// Foo {
+/// refcount: Cell::new(1),
+/// },
+/// flags::GFP_KERNEL,
+/// )?;
+/// let result = NonNull::new(KBox::into_raw(result)).ok_or(ENOMEM)?;
+/// // SAFETY: We just allocated the `Self`, thus it is valid and there cannot be any other
+/// // Rust references. Calling `into_raw()` makes us responsible for ownership and
+/// // we won't use the raw pointer anymore, thus we can transfer ownership to the `Owned`.
+/// Ok(unsafe { Owned::from_raw(result) })
+/// }
+/// }
+///
+/// // SAFETY: We increment and decrement each time the respective function is called and only free
+/// // the `Foo` when the refcount reaches zero.
+/// unsafe impl RefCounted for Foo {
+/// fn inc_ref(&self) {
+/// self.refcount.replace(self.refcount.get() + 1);
+/// }
+///
+/// unsafe fn dec_ref(this: NonNull<Self>) {
+/// // SAFETY: By requirement on calling this function, the refcount is non-zero,
+/// // implying the underlying object is valid.
+/// let refcount = unsafe { &this.as_ref().refcount };
+/// let new_refcount = refcount.get() - 1;
+/// if new_refcount == 0 {
+/// // The `Foo` will be dropped when `KBox` goes out of scope.
+/// // SAFETY: The [`KBox<Foo>`] is still alive as the old refcount is 1. We can pass
+/// // ownership to the [`KBox`] as by requirement on calling this function,
+/// // the `Self` will no longer be used by the caller.
+/// unsafe { KBox::from_raw(this.as_ptr()) };
+/// } else {
+/// refcount.replace(new_refcount);
+/// }
+/// }
+/// }
+///
+/// impl OwnableRefCounted for Foo {
+/// fn try_from_shared(this: ARef<Self>) -> Result<Owned<Self>, ARef<Self>> {
+/// if this.refcount.get() == 1 {
+/// // SAFETY: The `Foo` is still alive and has no other Rust references as the refcount
+/// // is 1.
+/// Ok(unsafe { Owned::from_raw(ARef::into_raw(this)) })
+/// } else {
+/// Err(this)
+/// }
+/// }
+/// }
+///
+/// // SAFETY: This implementation of `release()` is safe for any valid `Self`.
+/// unsafe impl Ownable for Foo {
+/// unsafe fn release(this: NonNull<Self>) {
+/// // SAFETY: Using `dec_ref()` from [`RefCounted`] to release is okay, as the refcount is
+/// // always 1 for an [`Owned<Foo>`].
+/// unsafe{ Foo::dec_ref(this) };
+/// }
+/// }
+///
+/// let foo = Foo::new()?;
+/// let mut foo = ARef::from(foo);
+/// {
+/// let bar = foo.clone();
+/// assert!(Owned::try_from(bar).is_err());
+/// }
+/// assert!(Owned::try_from(foo).is_ok());
+/// # Ok::<(), Error>(())
+/// ```
+pub trait OwnableRefCounted: RefCounted + Ownable + Sized {
+ /// Checks if the [`ARef`] is unique and converts it to an [`Owned`] if that is the case.
+ /// Otherwise it returns again an [`ARef`] to the same underlying object.
+ fn try_from_shared(this: ARef<Self>) -> Result<Owned<Self>, ARef<Self>>;
+
+ /// Converts the [`Owned`] into an [`ARef`].
+ fn into_shared(this: Owned<Self>) -> ARef<Self> {
+ // SAFETY: Safe by the requirements on implementing the trait.
+ unsafe { ARef::from_raw(Owned::into_raw(this)) }
+ }
+}
+
+impl<T: OwnableRefCounted> TryFrom<ARef<T>> for Owned<T> {
+ type Error = ARef<T>;
+ /// Tries to convert the [`ARef`] to an [`Owned`] by calling
+ /// [`try_from_shared()`](OwnableRefCounted::try_from_shared). In case the [`ARef`] is not
+ /// unique, it returns again an [`ARef`] to the same underlying object.
+ fn try_from(b: ARef<T>) -> Result<Owned<T>, Self::Error> {
+ T::try_from_shared(b)
+ }
+}
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index 3c63c9a5fb9be..77f6c8dc411eb 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -23,6 +23,10 @@
ops::Deref,
ptr::NonNull, //
};
+use kernel::types::{
+ OwnableRefCounted,
+ Owned, //
+};
/// Types that are internally reference counted.
///
@@ -35,7 +39,10 @@
/// Note: Implementing this trait allows types to be wrapped in an [`ARef<Self>`]. It requires an
/// internal reference count and provides only shared references. If unique references are required
/// [`Ownable`](crate::types::Ownable) should be implemented which allows types to be wrapped in an
-/// [`Owned<Self>`](crate::types::Owned).
+/// [`Owned<Self>`](crate::types::Owned). Implementing the trait
+/// [`OwnableRefCounted`] allows to convert between unique and
+/// shared references (i.e. [`Owned<Self>`](crate::types::Owned) and
+/// [`ARef<Self>`](crate::types::Owned)).
///
/// # Safety
///
@@ -185,6 +192,12 @@ fn from(b: &T) -> Self {
}
}
+impl<T: OwnableRefCounted> From<Owned<T>> for ARef<T> {
+ fn from(b: Owned<T>) -> Self {
+ T::into_shared(b)
+ }
+}
+
impl<T: RefCounted> Drop for ARef<T> {
fn drop(&mut self) {
// SAFETY: The type invariants guarantee that the `ARef` owns the reference we're about to
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 9b96aa2ebdb7e..f43c091eeb8b7 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -14,6 +14,7 @@
pub use crate::{
owned::{
Ownable,
+ OwnableRefCounted,
Owned, //
},
sync::aref::{
--
2.51.2
^ permalink raw reply related
* [PATCH v15 3/9] rust: Add missing SAFETY documentation for `ARef` example
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg, Oliver Mangold
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
From: Oliver Mangold <oliver.mangold@pm.me>
SAFETY comment in rustdoc example was just 'TODO'. Fixed.
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/sync/aref.rs | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index 61caddfd89619..efe16a7fdfa5d 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -129,12 +129,14 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
/// # Examples
///
/// ```
- /// use core::ptr::NonNull;
- /// use kernel::sync::aref::{ARef, RefCounted};
+ /// # use core::ptr::NonNull;
+ /// # use kernel::sync::aref::{ARef, RefCounted};
///
/// struct Empty {}
///
- /// # // SAFETY: TODO.
+ /// // SAFETY: The `RefCounted` implementation for `Empty` does not count references and never
+ /// // frees the underlying object. Thus we can act as owning an increment on the refcount for
+ /// // the object that we pass to the newly created `ARef`.
/// unsafe impl RefCounted for Empty {
/// fn inc_ref(&self) {}
/// unsafe fn dec_ref(_obj: NonNull<Self>) {}
@@ -142,7 +144,7 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// let mut data = Empty {};
/// let ptr = NonNull::<Empty>::new(&mut data).unwrap();
- /// # // SAFETY: TODO.
+ /// // SAFETY: We keep `data` around longer than the `ARef`.
/// let data_ref: ARef<Empty> = unsafe { ARef::from_raw(ptr) };
/// let raw_ptr: NonNull<Empty> = ARef::into_raw(data_ref);
///
--
2.51.2
^ permalink raw reply related
* [PATCH v15 6/9] rust: page: update formatting of `use` statements
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
Update formatting in preparation for next patch
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/page.rs | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 432fc0297d4a8..bf3bed7e2d3fe 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -3,17 +3,23 @@
//! Kernel page allocation and management.
use crate::{
- alloc::{AllocError, Flags},
+ alloc::{
+ AllocError,
+ Flags, //
+ },
bindings,
error::code::*,
error::Result,
- uaccess::UserSliceReader,
+ uaccess::UserSliceReader, //
};
use core::{
marker::PhantomData,
mem::ManuallyDrop,
ops::Deref,
- ptr::{self, NonNull},
+ ptr::{
+ self,
+ NonNull, //
+ }, //
};
/// A bitwise shift for the page size.
--
2.51.2
^ permalink raw reply related
* [PATCH v15 9/9] rust: page: add `from_raw()`
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg, Andreas Hindborg
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
Add a method to `Page` that allows construction of an instance from `struct
page` pointer.
Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
---
rust/kernel/page.rs | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 4591b7b01c3d2..803f3e3d76b22 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -191,6 +191,17 @@ pub fn nid(&self) -> i32 {
unsafe { bindings::page_to_nid(self.as_ptr()) }
}
+ /// Create a `&Page` from a raw `struct page` pointer
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must be valid for use as a reference for the duration of `'a`.
+ pub unsafe fn from_raw<'a>(ptr: *const bindings::page) -> &'a Self {
+ // SAFETY: By function safety requirements, ptr is not null and is
+ // valid for use as a reference.
+ unsafe { &*Opaque::cast_from(ptr).cast::<Self>() }
+ }
+
/// Runs a piece of code with this page mapped to an address.
///
/// The page is unmapped when this call returns.
--
2.51.2
^ permalink raw reply related
* [PATCH v15 0/9] rust: add `Ownable` trait and `Owned` type
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg, Asahi Lina, Oliver Mangold, Viresh Kumar,
Asahi Lina, Andreas Hindborg
Add a new trait `Ownable` and type `Owned` for types that specify their
own way of performing allocation and destruction. This is useful for
types from the C side.
Add the trait `OwnableRefCounted` that allows conversion between
`ARef` and `Owned`. This is analogous to conversion between `Arc` and
`UniqueArc`.
Convert `Page` to be `Ownable` and add a `from_raw` method.
Implement `ForeignOwnable` for `Owned`.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
Changes in v15:
- Update series with original SoB's.
- Rename `AlwaysRefCounted` in `kernel::usb`.
- Rename `Owned::get_pin_mut` to `Owned::as_pin_mut`.
- Link to v14: https://msgid.link/20260204-unique-ref-v14-0-17cb29ebacbb@kernel.org
Changes in v14:
- Rebase on v6.19-rc7.
- Rewrite cover letter.
- Update documentation and safety comments based on v13 feedback.
- Update commit messages.
- Reorder implementation blocks in owned.rs.
- Update example in owned.rs to use try operator rather than `expect`.
- Reformat use statements.
- Add patch: rust: page: convert to `Ownable`.
- Add patch: rust: implement `ForeignOwnable` for `Owned`.
- Add patch: rust: page: add `from_raw()`.
- Link to v13: https://lore.kernel.org/r/20251117-unique-ref-v13-0-b5b243df1250@pm.me
Changes in v13:
- Rebase onto v6.18-rc1 (Andreas's work).
- Documentation and style fixes contributed by Andreas
- Link to v12: https://lore.kernel.org/r/20251001-unique-ref-v12-0-fa5c31f0c0c4@pm.me
Changes in v12:
-
- Rebase onto v6.17-rc1 (Andreas's work).
- moved kernel/types/ownable.rs to kernel/owned.rs
- Drop OwnableMut, make DerefMut depend on Unpin instead. I understood
ML discussion as that being okay, but probably needs further scrunity.
- Lots of more documentation changes suggested by reviewers.
- Usage example for Ownable/Owned.
- Link to v11: https://lore.kernel.org/r/20250618-unique-ref-v11-0-49eadcdc0aa6@pm.me
Changes in v11:
- Rework of documentation. I tried to honor all requests for changes "in
spirit" plus some clearifications and corrections of my own.
- Dropping `SimpleOwnedRefCounted` by request from Alice, as it creates a
potentially problematic blanket implementation (which a derive macro that
could be created later would not have).
- Dropping Miguel's "kbuild: provide `RUSTC_HAS_DO_NOT_RECOMMEND` symbol"
patch, as it is not needed anymore after dropping `SimpleOwnedRefCounted`.
(I can add it again, if it is considered useful anyway).
- Link to v10: https://lore.kernel.org/r/20250502-unique-ref-v10-0-25de64c0307f@pm.me
Changes in v10:
- Moved kernel/ownable.rs to kernel/types/ownable.rs
- Fixes in documentation / comments as suggested by Andreas Hindborg
- Added Reviewed-by comment for Andreas Hindborg
- Fix rustfmt of pid_namespace.rs
- Link to v9: https://lore.kernel.org/r/20250325-unique-ref-v9-0-e91618c1de26@pm.me
Changes in v9:
- Rebase onto v6.14-rc7
- Move Ownable/OwnedRefCounted/Ownable, etc., into separate module
- Documentation fixes to Ownable/OwnableMut/OwnableRefCounted
- Add missing SAFETY documentation to ARef example
- Link to v8: https://lore.kernel.org/r/20250313-unique-ref-v8-0-3082ffc67a31@pm.me
Changes in v8:
- Fix Co-developed-by and Suggested-by tags as suggested by Miguel and Boqun
- Some small documentation fixes in Owned/Ownable patch
- removing redundant trait constraint on DerefMut for Owned as suggested by Boqun Feng
- make SimpleOwnedRefCounted no longer implement RefCounted as suggested by Boqun Feng
- documentation for RefCounted as suggested by Boqun Feng
- Link to v7: https://lore.kernel.org/r/20250310-unique-ref-v7-0-4caddb78aa05@pm.me
Changes in v7:
- Squash patch to make Owned::from_raw/into_raw public into parent
- Added Signed-off-by to other people's commits
- Link to v6: https://lore.kernel.org/r/20250310-unique-ref-v6-0-1ff53558617e@pm.me
Changes in v6:
- Changed comments/formatting as suggested by Miguel Ojeda
- Included and used new config flag RUSTC_HAS_DO_NOT_RECOMMEND,
thus no changes to types.rs will be needed when the attribute
becomes available.
- Fixed commit message for Owned patch.
- Link to v5: https://lore.kernel.org/r/20250307-unique-ref-v5-0-bffeb633277e@pm.me
Changes in v5:
- Rebase the whole thing on top of the Ownable/Owned traits by Asahi Lina.
- Rename AlwaysRefCounted to RefCounted and make AlwaysRefCounted a
marker trait instead to allow to obtain an ARef<T> from an &T,
which (as Alice pointed out) is unsound when combined with UniqueRef/Owned.
- Change the Trait design and naming to implement this feature,
UniqueRef/UniqueRefCounted is dropped in favor of Ownable/Owned and
OwnableRefCounted is used to provide the functions to convert
between Owned and ARef.
- Link to v4: https://lore.kernel.org/r/20250305-unique-ref-v4-1-a8fdef7b1c2c@pm.me
Changes in v4:
- Just a minor change in naming by request from Andreas Hindborg,
try_shared_to_unique() -> try_from_shared(),
unique_to_shared() -> into_shared(),
which is more in line with standard Rust naming conventions.
- Link to v3: https://lore.kernel.org/r/Z8Wuud2UQX6Yukyr@mango
---
Andreas Hindborg (4):
rust: aref: update formatting of use statements
rust: page: update formatting of `use` statements
rust: implement `ForeignOwnable` for `Owned`
rust: page: add `from_raw()`
Asahi Lina (2):
rust: types: Add Ownable/Owned types
rust: page: convert to `Ownable`
Oliver Mangold (3):
rust: rename `AlwaysRefCounted` to `RefCounted`.
rust: Add missing SAFETY documentation for `ARef` example
rust: Add `OwnableRefCounted`
rust/kernel/auxiliary.rs | 7 +-
rust/kernel/block/mq/request.rs | 15 +-
rust/kernel/cred.rs | 13 +-
rust/kernel/device.rs | 10 +-
rust/kernel/device/property.rs | 7 +-
rust/kernel/drm/device.rs | 10 +-
rust/kernel/drm/gem/mod.rs | 8 +-
rust/kernel/fs/file.rs | 16 +-
rust/kernel/i2c.rs | 16 +-
rust/kernel/lib.rs | 1 +
rust/kernel/mm.rs | 15 +-
rust/kernel/mm/mmput_async.rs | 9 +-
rust/kernel/opp.rs | 10 +-
rust/kernel/owned.rs | 366 ++++++++++++++++++++++++++++++++++++++++
rust/kernel/page.rs | 57 +++++--
rust/kernel/pci.rs | 10 +-
rust/kernel/pid_namespace.rs | 12 +-
rust/kernel/platform.rs | 7 +-
rust/kernel/sync/aref.rs | 80 ++++++---
rust/kernel/task.rs | 10 +-
rust/kernel/types.rs | 13 +-
rust/kernel/usb.rs | 15 +-
22 files changed, 624 insertions(+), 83 deletions(-)
---
base-commit: b8d687c7eeb52d0353ac27c4f71594a2e6aa365f
change-id: 20250305-unique-ref-29fcd675f9e9
Best regards,
--
Andreas Hindborg <a.hindborg@kernel.org>
^ permalink raw reply
* [PATCH v15 2/9] rust: rename `AlwaysRefCounted` to `RefCounted`.
From: Andreas Hindborg @ 2026-02-20 9:51 UTC (permalink / raw)
To: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, Boqun Feng
Cc: linux-kernel, rust-for-linux, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-mm, linux-pm, linux-pci,
Andreas Hindborg, Oliver Mangold, Viresh Kumar
In-Reply-To: <20260220-unique-ref-v15-0-893ed86b06cc@kernel.org>
From: Oliver Mangold <oliver.mangold@pm.me>
There are types where it may both be reference counted in some cases and
owned in others. In such cases, obtaining `ARef<T>` from `&T` would be
unsound as it allows creation of `ARef<T>` copy from `&Owned<T>`.
Therefore, we split `AlwaysRefCounted` into `RefCounted` (which `ARef<T>`
would require) and a marker trait to indicate that the type is always
reference counted (and not `Ownable`) so the `&T` -> `ARef<T>` conversion
is possible.
- Rename `AlwaysRefCounted` to `RefCounted`.
- Add a new unsafe trait `AlwaysRefCounted`.
- Implement the new trait `AlwaysRefCounted` for the newly renamed
`RefCounted` implementations. This leaves functionality of existing
implementers of `AlwaysRefCounted` intact.
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
[ Andreas: Updated commit message and rebase on rust-6.20-7.0 ]
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/auxiliary.rs | 7 +++++-
rust/kernel/block/mq/request.rs | 15 +++++++------
rust/kernel/cred.rs | 13 ++++++++++--
rust/kernel/device.rs | 10 ++++++---
rust/kernel/device/property.rs | 7 +++++-
rust/kernel/drm/device.rs | 10 ++++++---
rust/kernel/drm/gem/mod.rs | 8 ++++---
rust/kernel/fs/file.rs | 16 ++++++++++----
rust/kernel/i2c.rs | 16 +++++++++-----
rust/kernel/mm.rs | 15 +++++++++----
rust/kernel/mm/mmput_async.rs | 9 ++++++--
rust/kernel/opp.rs | 10 ++++++---
rust/kernel/owned.rs | 2 +-
rust/kernel/pci.rs | 10 ++++++++-
rust/kernel/pid_namespace.rs | 12 +++++++++--
rust/kernel/platform.rs | 7 +++++-
rust/kernel/sync/aref.rs | 47 ++++++++++++++++++++++++++---------------
rust/kernel/task.rs | 10 ++++++---
rust/kernel/types.rs | 3 ++-
rust/kernel/usb.rs | 15 ++++++++++---
20 files changed, 176 insertions(+), 66 deletions(-)
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index 56f3c180e8f69..234003341294f 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -11,6 +11,7 @@
driver,
error::{from_result, to_result, Result},
prelude::*,
+ sync::aref::{AlwaysRefCounted, RefCounted},
types::Opaque,
ThisModule,
};
@@ -258,7 +259,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx>
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -277,6 +278,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs
index ce3e30c81cb5e..cf013b9e2cacf 100644
--- a/rust/kernel/block/mq/request.rs
+++ b/rust/kernel/block/mq/request.rs
@@ -9,7 +9,7 @@
block::mq::Operations,
error::Result,
sync::{
- aref::{ARef, AlwaysRefCounted},
+ aref::{ARef, AlwaysRefCounted, RefCounted},
atomic::Relaxed,
Refcount,
},
@@ -229,11 +229,10 @@ unsafe impl<T: Operations> Send for Request<T> {}
// mutate `self` are internally synchronized`
unsafe impl<T: Operations> Sync for Request<T> {}
-// SAFETY: All instances of `Request<T>` are reference counted. This
-// implementation of `AlwaysRefCounted` ensure that increments to the ref count
-// keeps the object alive in memory at least until a matching reference count
-// decrement is executed.
-unsafe impl<T: Operations> AlwaysRefCounted for Request<T> {
+// SAFETY: All instances of `Request<T>` are reference counted. This implementation of `RefCounted`
+// ensure that increments to the ref count keeps the object alive in memory at least until a
+// matching reference count decrement is executed.
+unsafe impl<T: Operations> RefCounted for Request<T> {
fn inc_ref(&self) {
self.wrapper_ref().refcount().inc();
}
@@ -255,3 +254,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
}
}
}
+
+// SAFETY: We currently do not implement `Ownable`, thus it is okay to obtain an `ARef<Request>`
+// from a `&Request` (but this will change in the future).
+unsafe impl<T: Operations> AlwaysRefCounted for Request<T> {}
diff --git a/rust/kernel/cred.rs b/rust/kernel/cred.rs
index ffa156b9df377..20ef0144094be 100644
--- a/rust/kernel/cred.rs
+++ b/rust/kernel/cred.rs
@@ -8,7 +8,12 @@
//!
//! Reference: <https://www.kernel.org/doc/html/latest/security/credentials.html>
-use crate::{bindings, sync::aref::AlwaysRefCounted, task::Kuid, types::Opaque};
+use crate::{
+ bindings,
+ sync::aref::RefCounted,
+ task::Kuid,
+ types::{AlwaysRefCounted, Opaque},
+};
/// Wraps the kernel's `struct cred`.
///
@@ -76,7 +81,7 @@ pub fn euid(&self) -> Kuid {
}
// SAFETY: The type invariants guarantee that `Credential` is always ref-counted.
-unsafe impl AlwaysRefCounted for Credential {
+unsafe impl RefCounted for Credential {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -90,3 +95,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Credential>) {
unsafe { bindings::put_cred(obj.cast().as_ptr()) };
}
}
+
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Credential>` from a
+// `&Credential`.
+unsafe impl AlwaysRefCounted for Credential {}
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 71b200df0f400..2a3bed19b9495 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -7,8 +7,8 @@
use crate::{
bindings, fmt,
prelude::*,
- sync::aref::ARef,
- types::{ForeignOwnable, Opaque},
+ sync::aref::{ARef, RefCounted},
+ types::{AlwaysRefCounted, ForeignOwnable, Opaque},
};
use core::{any::TypeId, marker::PhantomData, ptr};
@@ -490,7 +490,7 @@ pub fn fwnode(&self) -> Option<&property::FwNode> {
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_raw()) };
@@ -502,6 +502,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
// SAFETY: As by the type invariant `Device` can be sent to any thread.
unsafe impl Send for Device {}
diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs
index 3a332a8c53a9e..a8bb824ad0ec1 100644
--- a/rust/kernel/device/property.rs
+++ b/rust/kernel/device/property.rs
@@ -14,6 +14,7 @@
fmt,
prelude::*,
str::{CStr, CString},
+ sync::aref::{AlwaysRefCounted, RefCounted},
types::{ARef, Opaque},
};
@@ -359,7 +360,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
}
// SAFETY: Instances of `FwNode` are always reference-counted.
-unsafe impl crate::types::AlwaysRefCounted for FwNode {
+unsafe impl RefCounted for FwNode {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the
// refcount is non-zero.
@@ -373,6 +374,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<FwNode>` from a
+// `&FwNode`.
+unsafe impl AlwaysRefCounted for FwNode {}
+
enum Node<'a> {
Borrowed(&'a FwNode),
Owned(ARef<FwNode>),
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 3ce8f62a00569..38ce7f389ed00 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -11,8 +11,8 @@
error::from_err_ptr,
error::Result,
prelude::*,
- sync::aref::{ARef, AlwaysRefCounted},
- types::Opaque,
+ sync::aref::{AlwaysRefCounted, RefCounted},
+ types::{ARef, Opaque},
};
use core::{alloc::Layout, mem, ops::Deref, ptr, ptr::NonNull};
@@ -198,7 +198,7 @@ fn deref(&self) -> &Self::Target {
// SAFETY: DRM device objects are always reference counted and the get/put functions
// satisfy the requirements.
-unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {
+unsafe impl<T: drm::Driver> RefCounted for Device<T> {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::drm_dev_get(self.as_raw()) };
@@ -213,6 +213,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {}
+
impl<T: drm::Driver> AsRef<device::Device> for Device<T> {
fn as_ref(&self) -> &device::Device {
// SAFETY: `bindings::drm_device::dev` is valid as long as the DRM device itself is valid,
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index a7f682e95c018..ad6840a440165 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -10,8 +10,7 @@
drm::driver::{AllocImpl, AllocOps},
error::{to_result, Result},
prelude::*,
- sync::aref::{ARef, AlwaysRefCounted},
- types::Opaque,
+ types::{ARef, AlwaysRefCounted, Opaque},
};
use core::{ops::Deref, ptr::NonNull};
@@ -253,7 +252,7 @@ extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
}
// SAFETY: Instances of `Object<T>` are always reference-counted.
-unsafe impl<T: DriverObject> crate::types::AlwaysRefCounted for Object<T> {
+unsafe impl<T: DriverObject> crate::types::RefCounted for Object<T> {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::drm_gem_object_get(self.as_raw()) };
@@ -267,6 +266,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
unsafe { bindings::drm_gem_object_put(obj.as_raw()) }
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Object`.
+unsafe impl<T: DriverObject> crate::types::AlwaysRefCounted for Object<T> {}
impl<T: DriverObject> super::private::Sealed for Object<T> {}
diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 23ee689bd2400..06e457d62a939 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -12,8 +12,8 @@
cred::Credential,
error::{code::*, to_result, Error, Result},
fmt,
- sync::aref::{ARef, AlwaysRefCounted},
- types::{NotThreadSafe, Opaque},
+ sync::aref::RefCounted,
+ types::{ARef, AlwaysRefCounted, NotThreadSafe, Opaque},
};
use core::ptr;
@@ -197,7 +197,7 @@ unsafe impl Sync for File {}
// SAFETY: The type invariants guarantee that `File` is always ref-counted. This implementation
// makes `ARef<File>` own a normal refcount.
-unsafe impl AlwaysRefCounted for File {
+unsafe impl RefCounted for File {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -212,6 +212,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<File>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<File>` from a
+// `&File`.
+unsafe impl AlwaysRefCounted for File {}
+
/// Wraps the kernel's `struct file`. Not thread safe.
///
/// This type represents a file that is not known to be safe to transfer across thread boundaries.
@@ -233,7 +237,7 @@ pub struct LocalFile {
// SAFETY: The type invariants guarantee that `LocalFile` is always ref-counted. This implementation
// makes `ARef<LocalFile>` own a normal refcount.
-unsafe impl AlwaysRefCounted for LocalFile {
+unsafe impl RefCounted for LocalFile {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -249,6 +253,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<LocalFile>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<LocalFile>` from a
+// `&LocalFile`.
+unsafe impl AlwaysRefCounted for LocalFile {}
+
impl LocalFile {
/// Constructs a new `struct file` wrapper from a file descriptor.
///
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 792a71b154630..683950057423d 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -17,8 +17,10 @@
of,
prelude::*,
types::{
+ ARef,
AlwaysRefCounted,
- Opaque, //
+ Opaque,
+ RefCounted, //
}, //
};
@@ -31,8 +33,6 @@
}, //
};
-use kernel::types::ARef;
-
/// An I2C device id table.
#[repr(transparent)]
#[derive(Clone, Copy)]
@@ -407,7 +407,7 @@ pub fn get(index: i32) -> Result<ARef<Self>> {
kernel::impl_device_context_into_aref!(I2cAdapter);
// SAFETY: Instances of `I2cAdapter` are always reference-counted.
-unsafe impl crate::types::AlwaysRefCounted for I2cAdapter {
+unsafe impl crate::types::RefCounted for I2cAdapter {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::i2c_get_adapter(self.index()) };
@@ -418,6 +418,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
unsafe { bindings::i2c_put_adapter(obj.as_ref().as_raw()) }
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from an
+// `&I2cAdapter`.
+unsafe impl AlwaysRefCounted for I2cAdapter {}
/// The i2c board info representation
///
@@ -483,7 +486,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for I2cClient<C
kernel::impl_device_context_into_aref!(I2cClient);
// SAFETY: Instances of `I2cClient` are always reference-counted.
-unsafe impl AlwaysRefCounted for I2cClient {
+unsafe impl RefCounted for I2cClient {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -494,6 +497,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
unsafe { bindings::put_device(&raw mut (*obj.as_ref().as_raw()).dev) }
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from an
+// `&I2cClient`.
+unsafe impl AlwaysRefCounted for I2cClient {}
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for I2cClient<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs
index 4764d7b68f2a7..dd9e3969e7206 100644
--- a/rust/kernel/mm.rs
+++ b/rust/kernel/mm.rs
@@ -13,8 +13,8 @@
use crate::{
bindings,
- sync::aref::{ARef, AlwaysRefCounted},
- types::{NotThreadSafe, Opaque},
+ sync::aref::RefCounted,
+ types::{ARef, AlwaysRefCounted, NotThreadSafe, Opaque},
};
use core::{ops::Deref, ptr::NonNull};
@@ -55,7 +55,7 @@ unsafe impl Send for Mm {}
unsafe impl Sync for Mm {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for Mm {
+unsafe impl RefCounted for Mm {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -69,6 +69,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Mm>` from a `&Mm`.
+unsafe impl AlwaysRefCounted for Mm {}
+
/// A wrapper for the kernel's `struct mm_struct`.
///
/// This type is like [`Mm`], but with non-zero `mm_users`. It can only be used when `mm_users` can
@@ -91,7 +94,7 @@ unsafe impl Send for MmWithUser {}
unsafe impl Sync for MmWithUser {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for MmWithUser {
+unsafe impl RefCounted for MmWithUser {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -105,6 +108,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<MmWithUser>` from a
+// `&MmWithUser`.
+unsafe impl AlwaysRefCounted for MmWithUser {}
+
// Make all `Mm` methods available on `MmWithUser`.
impl Deref for MmWithUser {
type Target = Mm;
diff --git a/rust/kernel/mm/mmput_async.rs b/rust/kernel/mm/mmput_async.rs
index b8d2f051225c7..aba4ce675c860 100644
--- a/rust/kernel/mm/mmput_async.rs
+++ b/rust/kernel/mm/mmput_async.rs
@@ -10,7 +10,8 @@
use crate::{
bindings,
mm::MmWithUser,
- sync::aref::{ARef, AlwaysRefCounted},
+ sync::aref::RefCounted,
+ types::{ARef, AlwaysRefCounted},
};
use core::{ops::Deref, ptr::NonNull};
@@ -34,7 +35,7 @@ unsafe impl Send for MmWithUserAsync {}
unsafe impl Sync for MmWithUserAsync {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for MmWithUserAsync {
+unsafe impl RefCounted for MmWithUserAsync {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -48,6 +49,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<MmWithUserAsync>`
+// from a `&MmWithUserAsync`.
+unsafe impl AlwaysRefCounted for MmWithUserAsync {}
+
// Make all `MmWithUser` methods available on `MmWithUserAsync`.
impl Deref for MmWithUserAsync {
type Target = MmWithUser;
diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs
index a760fac287655..06fe2ca776a4f 100644
--- a/rust/kernel/opp.rs
+++ b/rust/kernel/opp.rs
@@ -16,8 +16,8 @@
ffi::{c_char, c_ulong},
prelude::*,
str::CString,
- sync::aref::{ARef, AlwaysRefCounted},
- types::Opaque,
+ sync::aref::RefCounted,
+ types::{ARef, AlwaysRefCounted, Opaque},
};
#[cfg(CONFIG_CPU_FREQ)]
@@ -1041,7 +1041,7 @@ unsafe impl Send for OPP {}
unsafe impl Sync for OPP {}
/// SAFETY: The type invariants guarantee that [`OPP`] is always refcounted.
-unsafe impl AlwaysRefCounted for OPP {
+unsafe impl RefCounted for OPP {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
unsafe { bindings::dev_pm_opp_get(self.0.get()) };
@@ -1053,6 +1053,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<OPP>` from an
+// `&OPP`.
+unsafe impl AlwaysRefCounted for OPP {}
+
impl OPP {
/// Creates an owned reference to a [`OPP`] from a valid pointer.
///
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index d566ad0aa1c99..b8d3b9c725cf6 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -25,7 +25,7 @@
///
/// Note: The underlying object is not required to provide internal reference counting, because it
/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
-/// [`AlwaysRefCounted`](crate::types::AlwaysRefCounted) should be implemented.
+/// [`RefCounted`](crate::types::RefCounted) should be implemented.
///
/// # Safety
///
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 82e128431f080..a73551dedee8f 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -19,6 +19,10 @@
},
prelude::*,
str::CStr,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque,
ThisModule, //
};
@@ -458,7 +462,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx>
impl crate::dma::Device for Device<device::Core> {}
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::pci_dev_get(self.as_raw()) };
@@ -470,6 +474,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/pid_namespace.rs b/rust/kernel/pid_namespace.rs
index 979a9718f153d..4f6a94540e33d 100644
--- a/rust/kernel/pid_namespace.rs
+++ b/rust/kernel/pid_namespace.rs
@@ -7,7 +7,11 @@
//! C header: [`include/linux/pid_namespace.h`](srctree/include/linux/pid_namespace.h) and
//! [`include/linux/pid.h`](srctree/include/linux/pid.h)
-use crate::{bindings, sync::aref::AlwaysRefCounted, types::Opaque};
+use crate::{
+ bindings,
+ sync::aref::RefCounted,
+ types::{AlwaysRefCounted, Opaque},
+};
use core::ptr;
/// Wraps the kernel's `struct pid_namespace`. Thread safe.
@@ -41,7 +45,7 @@ pub unsafe fn from_ptr<'a>(ptr: *const bindings::pid_namespace) -> &'a Self {
}
// SAFETY: Instances of `PidNamespace` are always reference-counted.
-unsafe impl AlwaysRefCounted for PidNamespace {
+unsafe impl RefCounted for PidNamespace {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -55,6 +59,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<PidNamespace>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<PidNamespace>` from
+// a `&PidNamespace`.
+unsafe impl AlwaysRefCounted for PidNamespace {}
+
// SAFETY:
// - `PidNamespace::dec_ref` can be called from any thread.
// - It is okay to send ownership of `PidNamespace` across thread boundaries.
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index ed889f079cab6..9f1cd0b8fb0bc 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -13,6 +13,7 @@
irq::{self, IrqRequest},
of,
prelude::*,
+ sync::aref::{AlwaysRefCounted, RefCounted},
types::Opaque,
ThisModule,
};
@@ -481,7 +482,7 @@ pub fn optional_irq_by_name(&self, name: &CStr) -> Result<IrqRequest<'_>> {
impl crate::dma::Device for Device<device::Core> {}
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -493,6 +494,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index e175aefe86151..61caddfd89619 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -19,11 +19,9 @@
use core::{marker::PhantomData, mem::ManuallyDrop, ops::Deref, ptr::NonNull};
-/// Types that are _always_ reference counted.
+/// Types that are internally reference counted.
///
/// It allows such types to define their own custom ref increment and decrement functions.
-/// Additionally, it allows users to convert from a shared reference `&T` to an owned reference
-/// [`ARef<T>`].
///
/// This is usually implemented by wrappers to existing structures on the C side of the code. For
/// Rust code, the recommendation is to use [`Arc`](crate::sync::Arc) to create reference-counted
@@ -40,9 +38,8 @@
/// at least until matching decrements are performed.
///
/// Implementers must also ensure that all instances are reference-counted. (Otherwise they
-/// won't be able to honour the requirement that [`AlwaysRefCounted::inc_ref`] keep the object
-/// alive.)
-pub unsafe trait AlwaysRefCounted {
+/// won't be able to honour the requirement that [`RefCounted::inc_ref`] keep the object alive.)
+pub unsafe trait RefCounted {
/// Increments the reference count on the object.
fn inc_ref(&self);
@@ -55,11 +52,27 @@ pub unsafe trait AlwaysRefCounted {
/// Callers must ensure that there was a previous matching increment to the reference count,
/// and that the object is no longer used after its reference count is decremented (as it may
/// result in the object being freed), unless the caller owns another increment on the refcount
- /// (e.g., it calls [`AlwaysRefCounted::inc_ref`] twice, then calls
- /// [`AlwaysRefCounted::dec_ref`] once).
+ /// (e.g., it calls [`RefCounted::inc_ref`] twice, then calls [`RefCounted::dec_ref`] once).
unsafe fn dec_ref(obj: NonNull<Self>);
}
+/// Always reference-counted type.
+///
+/// It allows deriving a counted reference [`ARef<T>`] from a `&T`.
+///
+/// This provides some convenience, but it allows "escaping" borrow checks on `&T`. As it
+/// complicates attempts to ensure that a reference to T is unique, it is optional to provide for
+/// [`RefCounted`] types. See *Safety* below.
+///
+/// # Safety
+///
+/// Implementers must ensure that no safety invariants are violated by upgrading an `&T` to an
+/// [`ARef<T>`]. In particular that implies [`AlwaysRefCounted`] and [`crate::types::Ownable`]
+/// cannot be implemented for the same type, as this would allow violating the uniqueness guarantee
+/// of [`crate::types::Owned<T>`] by dereferencing it into an `&T` and obtaining an [`ARef`] from
+/// that.
+pub unsafe trait AlwaysRefCounted: RefCounted {}
+
/// An owned reference to an always-reference-counted object.
///
/// The object's reference count is automatically decremented when an instance of [`ARef`] is
@@ -70,7 +83,7 @@ pub unsafe trait AlwaysRefCounted {
///
/// The pointer stored in `ptr` is non-null and valid for the lifetime of the [`ARef`] instance. In
/// particular, the [`ARef`] instance owns an increment on the underlying object's reference count.
-pub struct ARef<T: AlwaysRefCounted> {
+pub struct ARef<T: RefCounted> {
ptr: NonNull<T>,
_p: PhantomData<T>,
}
@@ -79,16 +92,16 @@ pub struct ARef<T: AlwaysRefCounted> {
// it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
// `T` to be `Send` because any thread that has an `ARef<T>` may ultimately access `T` using a
// mutable reference, for example, when the reference count reaches zero and `T` is dropped.
-unsafe impl<T: AlwaysRefCounted + Sync + Send> Send for ARef<T> {}
+unsafe impl<T: RefCounted + Sync + Send> Send for ARef<T> {}
// SAFETY: It is safe to send `&ARef<T>` to another thread when the underlying `T` is `Sync`
// because it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally,
// it needs `T` to be `Send` because any thread that has a `&ARef<T>` may clone it and get an
// `ARef<T>` on that thread, so the thread may ultimately access `T` using a mutable reference, for
// example, when the reference count reaches zero and `T` is dropped.
-unsafe impl<T: AlwaysRefCounted + Sync + Send> Sync for ARef<T> {}
+unsafe impl<T: RefCounted + Sync + Send> Sync for ARef<T> {}
-impl<T: AlwaysRefCounted> ARef<T> {
+impl<T: RefCounted> ARef<T> {
/// Creates a new instance of [`ARef`].
///
/// It takes over an increment of the reference count on the underlying object.
@@ -117,12 +130,12 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// ```
/// use core::ptr::NonNull;
- /// use kernel::sync::aref::{ARef, AlwaysRefCounted};
+ /// use kernel::sync::aref::{ARef, RefCounted};
///
/// struct Empty {}
///
/// # // SAFETY: TODO.
- /// unsafe impl AlwaysRefCounted for Empty {
+ /// unsafe impl RefCounted for Empty {
/// fn inc_ref(&self) {}
/// unsafe fn dec_ref(_obj: NonNull<Self>) {}
/// }
@@ -140,7 +153,7 @@ pub fn into_raw(me: Self) -> NonNull<T> {
}
}
-impl<T: AlwaysRefCounted> Clone for ARef<T> {
+impl<T: RefCounted> Clone for ARef<T> {
fn clone(&self) -> Self {
self.inc_ref();
// SAFETY: We just incremented the refcount above.
@@ -148,7 +161,7 @@ fn clone(&self) -> Self {
}
}
-impl<T: AlwaysRefCounted> Deref for ARef<T> {
+impl<T: RefCounted> Deref for ARef<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
@@ -165,7 +178,7 @@ fn from(b: &T) -> Self {
}
}
-impl<T: AlwaysRefCounted> Drop for ARef<T> {
+impl<T: RefCounted> Drop for ARef<T> {
fn drop(&mut self) {
// SAFETY: The type invariants guarantee that the `ARef` owns the reference we're about to
// decrement.
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 49fad6de06740..0a6e38d984560 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -9,8 +9,8 @@
ffi::{c_int, c_long, c_uint},
mm::MmWithUser,
pid_namespace::PidNamespace,
- sync::aref::ARef,
- types::{NotThreadSafe, Opaque},
+ sync::aref::{AlwaysRefCounted, RefCounted},
+ types::{ARef, NotThreadSafe, Opaque},
};
use core::{
cmp::{Eq, PartialEq},
@@ -348,7 +348,7 @@ pub fn active_pid_ns(&self) -> Option<&PidNamespace> {
}
// SAFETY: The type invariants guarantee that `Task` is always refcounted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Task {
+unsafe impl RefCounted for Task {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -362,6 +362,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Task>` from a
+// `&Task`.
+unsafe impl AlwaysRefCounted for Task {}
+
impl Kuid {
/// Get the current euid.
#[inline]
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 4aec7b699269a..9b96aa2ebdb7e 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -18,7 +18,8 @@
},
sync::aref::{
ARef,
- AlwaysRefCounted, //
+ AlwaysRefCounted,
+ RefCounted, //
}, //
};
diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index d10b65e9fb6ad..089823b608333 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -12,7 +12,8 @@
error::{from_result, to_result, Result},
prelude::*,
str::CStr,
- types::{AlwaysRefCounted, Opaque},
+ sync::aref::{AlwaysRefCounted, RefCounted},
+ types::Opaque,
ThisModule,
};
use core::{
@@ -365,7 +366,7 @@ fn as_ref(&self) -> &Device {
}
// SAFETY: Instances of `Interface` are always reference-counted.
-unsafe impl AlwaysRefCounted for Interface {
+unsafe impl RefCounted for Interface {
fn inc_ref(&self) {
// SAFETY: The invariants of `Interface` guarantee that `self.as_raw()`
// returns a valid `struct usb_interface` pointer, for which we will
@@ -379,6 +380,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Interface>` from a
+// `&Interface`.
+unsafe impl AlwaysRefCounted for Interface {}
+
// SAFETY: A `Interface` is always reference-counted and can be released from any thread.
unsafe impl Send for Interface {}
@@ -416,7 +421,7 @@ fn as_raw(&self) -> *mut bindings::usb_device {
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The invariants of `Device` guarantee that `self.as_raw()`
// returns a valid `struct usb_device` pointer, for which we will
@@ -430,6 +435,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
--
2.51.2
^ permalink raw reply related
* Re: [PATCH v15 1/9] rust: types: Add Ownable/Owned types
From: Alice Ryhl @ 2026-02-20 10:35 UTC (permalink / raw)
To: Andreas Hindborg
Cc: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, linux-kernel, rust-for-linux, linux-block,
linux-security-module, dri-devel, linux-fsdevel, linux-mm,
linux-pm, linux-pci, Asahi Lina, Oliver Mangold
In-Reply-To: <20260220-unique-ref-v15-1-893ed86b06cc@kernel.org>
On Fri, Feb 20, 2026 at 10:51:10AM +0100, Andreas Hindborg wrote:
> From: Asahi Lina <lina+kernel@asahilina.net>
>
> By analogy to `AlwaysRefCounted` and `ARef`, an `Ownable` type is a
> (typically C FFI) type that *may* be owned by Rust, but need not be. Unlike
> `AlwaysRefCounted`, this mechanism expects the reference to be unique
> within Rust, and does not allow cloning.
>
> Conceptually, this is similar to a `KBox<T>`, except that it delegates
> resource management to the `T` instead of using a generic allocator.
>
> [ om:
> - Split code into separate file and `pub use` it from types.rs.
> - Make from_raw() and into_raw() public.
> - Remove OwnableMut, and make DerefMut dependent on Unpin instead.
> - Usage example/doctest for Ownable/Owned.
> - Fixes to documentation and commit message.
> ]
>
> Link: https://lore.kernel.org/all/20250202-rust-page-v1-1-e3170d7fe55e@asahilina.net/
> Signed-off-by: Asahi Lina <lina+kernel@asahilina.net>
> Co-developed-by: Oliver Mangold <oliver.mangold@pm.me>
> Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
> Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
> [ Andreas: Updated documentation, examples, and formatting ]
> Reviewed-by: Gary Guo <gary@garyguo.net>
> Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> +/// let result = NonNull::new(KBox::into_raw(result))
> +/// .expect("Raw pointer to newly allocation KBox is null, this should never happen.");
KBox should probably have an into_raw_nonnull().
> +/// let foo = Foo::new().expect("Failed to allocate a Foo. This shouldn't happen");
> +/// assert!(*FOO_ALLOC_COUNT.lock() == 1);
Use ? here.
> +/// }
> +/// // `foo` is out of scope now, so we expect no live allocations.
> +/// assert!(*FOO_ALLOC_COUNT.lock() == 0);
> +/// ```
> +pub unsafe trait Ownable {
> + /// Releases the object.
> + ///
> + /// # Safety
> + ///
> + /// Callers must ensure that:
> + /// - `this` points to a valid `Self`.
> + /// - `*this` is no longer used after this call.
> + unsafe fn release(this: NonNull<Self>);
Honestly, not using it after this call may be too strong. I can imagine
wanting a value where I have both an ARef<_> and Owned<_> reference to
something similar to the existing Arc<_>/ListArc<_> pattern, and in that
case the value may in fact be accessed after this call if you still have
an ARef<_>.
If you modify Owned<_> invariants and Owned::from_raw() safety
requirements along the lines of what I say below, then this could just
say that the caller must have permission to call this function. The
concrete implementer can specify what that means more directly, but here
all it means is that a prior call to Owned::from_raw() promised to give
you permission to call it.
> +/// A mutable reference to an owned `T`.
> +///
> +/// The [`Ownable`] is automatically freed or released when an instance of [`Owned`] is
> +/// dropped.
> +///
> +/// # Invariants
> +///
> +/// - The [`Owned<T>`] has exclusive access to the instance of `T`.
> +/// - The instance of `T` will stay alive at least as long as the [`Owned<T>`] is alive.
> +pub struct Owned<T: Ownable> {
> + ptr: NonNull<T>,
> +}
I think some more direct and less fuzzy invariants would be:
- This `Owned<T>` holds permissions to call `T::release()` on the value once.
- Until `T::release()` is called, this `Owned<T>` may perform mutable access on the `T`.
- The `T` value is pinned.
> + /// Get a pinned mutable reference to the data owned by this `Owned<T>`.
> + pub fn as_pin_mut(&mut self) -> Pin<&mut T> {
> + // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
> + // return a mutable reference to it.
> + let unpinned = unsafe { self.ptr.as_mut() };
> +
> + // SAFETY: We never hand out unpinned mutable references to the data in
> + // `Self`, unless the contained type is `Unpin`.
> + unsafe { Pin::new_unchecked(unpinned) }
I'd prefer if "pinned" was a type invariant, rather than make an
argument about what kind of APIs exist.
> +impl<T: Ownable + Unpin> DerefMut for Owned<T> {
> + fn deref_mut(&mut self) -> &mut Self::Target {
> + // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
> + // return a mutable reference to it.
> + unsafe { self.ptr.as_mut() }
Surely this safety comment should say something about pinning.
Alice
^ permalink raw reply
* Re: [PATCH] task: delete task_euid()
From: Alice Ryhl @ 2026-02-20 10:43 UTC (permalink / raw)
To: Paul Moore, Serge Hallyn, Jonathan Corbet, Greg Kroah-Hartman,
Shuah Khan, Alex Shi, Yanteng Si, Dongliang Mu
Cc: Miguel Ojeda, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Andreas Hindborg, Trevor Gross, Danilo Krummrich,
linux-security-module, linux-doc, linux-kernel, rust-for-linux,
Jann Horn
In-Reply-To: <20260219-remove-task-euid-v1-1-904060826e07@google.com>
On Thu, Feb 19, 2026 at 12:14:39PM +0000, Alice Ryhl wrote:
> include/linux/cred.h | 1 -
I guess the title of this should probably be
cred: delete task_euid()
rather than use the 'task:' prefix.
Alice
^ permalink raw reply
* Re: [PATCH v15 9/9] rust: page: add `from_raw()`
From: Alice Ryhl @ 2026-02-20 10:49 UTC (permalink / raw)
To: Andreas Hindborg
Cc: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, linux-kernel, rust-for-linux, linux-block,
linux-security-module, dri-devel, linux-fsdevel, linux-mm,
linux-pm, linux-pci
In-Reply-To: <20260220-unique-ref-v15-9-893ed86b06cc@kernel.org>
On Fri, Feb 20, 2026 at 10:52 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
> Add a method to `Page` that allows construction of an instance from `struct
> page` pointer.
>
> Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
> ---
> rust/kernel/page.rs | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
> index 4591b7b01c3d2..803f3e3d76b22 100644
> --- a/rust/kernel/page.rs
> +++ b/rust/kernel/page.rs
> @@ -191,6 +191,17 @@ pub fn nid(&self) -> i32 {
> unsafe { bindings::page_to_nid(self.as_ptr()) }
> }
>
> + /// Create a `&Page` from a raw `struct page` pointer
> + ///
> + /// # Safety
> + ///
> + /// `ptr` must be valid for use as a reference for the duration of `'a`.
> + pub unsafe fn from_raw<'a>(ptr: *const bindings::page) -> &'a Self {
> + // SAFETY: By function safety requirements, ptr is not null and is
> + // valid for use as a reference.
> + unsafe { &*Opaque::cast_from(ptr).cast::<Self>() }
If you're going to do a pointer cast, then keep it simple and just do
&*ptr.cast().
Alice
^ permalink raw reply
* Re: [PATCH v15 3/9] rust: Add missing SAFETY documentation for `ARef` example
From: Alice Ryhl @ 2026-02-20 10:49 UTC (permalink / raw)
To: Andreas Hindborg
Cc: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, linux-kernel, rust-for-linux, linux-block,
linux-security-module, dri-devel, linux-fsdevel, linux-mm,
linux-pm, linux-pci, Oliver Mangold
In-Reply-To: <20260220-unique-ref-v15-3-893ed86b06cc@kernel.org>
On Fri, Feb 20, 2026 at 10:52 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
> From: Oliver Mangold <oliver.mangold@pm.me>
>
> SAFETY comment in rustdoc example was just 'TODO'. Fixed.
>
> Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
> Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
> rust/kernel/sync/aref.rs | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
> index 61caddfd89619..efe16a7fdfa5d 100644
> --- a/rust/kernel/sync/aref.rs
> +++ b/rust/kernel/sync/aref.rs
> @@ -129,12 +129,14 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
> /// # Examples
> ///
> /// ```
> - /// use core::ptr::NonNull;
> - /// use kernel::sync::aref::{ARef, RefCounted};
> + /// # use core::ptr::NonNull;
> + /// # use kernel::sync::aref::{ARef, RefCounted};
> ///
Either keep the imports visible or delete this empty line. And either
way, it doesn't really fit in this commit.
> /// struct Empty {}
> ///
> - /// # // SAFETY: TODO.
> + /// // SAFETY: The `RefCounted` implementation for `Empty` does not count references and never
> + /// // frees the underlying object. Thus we can act as owning an increment on the refcount for
> + /// // the object that we pass to the newly created `ARef`.
> /// unsafe impl RefCounted for Empty {
> /// fn inc_ref(&self) {}
> /// unsafe fn dec_ref(_obj: NonNull<Self>) {}
> @@ -142,7 +144,7 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
> ///
> /// let mut data = Empty {};
> /// let ptr = NonNull::<Empty>::new(&mut data).unwrap();
> - /// # // SAFETY: TODO.
> + /// // SAFETY: We keep `data` around longer than the `ARef`.
> /// let data_ref: ARef<Empty> = unsafe { ARef::from_raw(ptr) };
> /// let raw_ptr: NonNull<Empty> = ARef::into_raw(data_ref);
> ///
>
> --
> 2.51.2
>
>
^ permalink raw reply
* Re: [PATCH v5 2/9] landlock: Control pathname UNIX domain socket resolution by path
From: Günther Noack @ 2026-02-20 14:33 UTC (permalink / raw)
To: Mickaël Salaün
Cc: John Johansen, Tingmao Wang, Justin Suess, Jann Horn,
linux-security-module, Samasth Norway Ananda, Matthieu Buffet,
Mikhail Ivanov, konstantin.meskhidze, Demi Marie Obenour,
Alyssa Ross, Tahera Fahimi, netdev
In-Reply-To: <20260217.lievaS8eeng8@digikod.net>
+netdev, we could use some advice on the locking approach in af_unix (see below)
On Wed, Feb 18, 2026 at 10:37:14AM +0100, Mickaël Salaün wrote:
> On Sun, Feb 15, 2026 at 11:51:50AM +0100, Günther Noack wrote:
> > diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
> > index f88fa1f68b77..3a8fc3af0d64 100644
> > --- a/include/uapi/linux/landlock.h
> > +++ b/include/uapi/linux/landlock.h
> > @@ -248,6 +248,15 @@ struct landlock_net_port_attr {
> > *
> > * This access right is available since the fifth version of the Landlock
> > * ABI.
> > + * - %LANDLOCK_ACCESS_FS_RESOLVE_UNIX: Look up pathname UNIX domain sockets
> > + * (:manpage:`unix(7)`). On UNIX domain sockets, this restricts both calls to
> > + * :manpage:`connect(2)` as well as calls to :manpage:`sendmsg(2)` with an
> > + * explicit recipient address.
> > + *
> > + * This access right only applies to connections to UNIX server sockets which
> > + * were created outside of the newly created Landlock domain (e.g. from within
> > + * a parent domain or from an unrestricted process). Newly created UNIX
> > + * servers within the same Landlock domain continue to be accessible.
>
> It might help to add a reference to the explicit scope mechanism.
>
> Please squash patch 9/9 into this one and also add a reference here to
> the rationale described in security/landlock.rst
Sounds good, will do.
> > +static void unmask_scoped_access(const struct landlock_ruleset *const client,
> > + const struct landlock_ruleset *const server,
> > + struct layer_access_masks *const masks,
> > + const access_mask_t access)
>
> This helper should be moved to task.c and factored out with
> domain_is_scoped(). This should be a dedicated patch.
(already discussed in another follow-up mail)
> > +static int hook_unix_find(const struct path *const path, struct sock *other,
> > + int flags)
> > +{
> > + const struct landlock_ruleset *dom_other;
> > + const struct landlock_cred_security *subject;
> > + struct layer_access_masks layer_masks;
> > + struct landlock_request request = {};
> > + static const struct access_masks fs_resolve_unix = {
> > + .fs = LANDLOCK_ACCESS_FS_RESOLVE_UNIX,
> > + };
> > +
> > + /* Lookup for the purpose of saving coredumps is OK. */
> > + if (unlikely(flags & SOCK_COREDUMP))
> > + return 0;
> > +
> > + /* Access to the same (or a lower) domain is always allowed. */
> > + subject = landlock_get_applicable_subject(current_cred(),
> > + fs_resolve_unix, NULL);
> > +
> > + if (!subject)
> > + return 0;
> > +
> > + if (!landlock_init_layer_masks(subject->domain, fs_resolve_unix.fs,
> > + &layer_masks, LANDLOCK_KEY_INODE))
> > + return 0;
> > +
> > + /* Checks the layers in which we are connecting within the same domain. */
> > + dom_other = landlock_cred(other->sk_socket->file->f_cred)->domain;
>
> We need to call unix_state_lock(other) before reading it, and check for
> SOCK_DEAD, and check sk_socket before dereferencing it. Indeed,
> the socket can be make orphan (see unix_dgram_sendmsg and
> unix_stream_connect). I *think* a socket cannot be "resurrected" or
> recycled once dead, so we may assume there is no race condition wrt
> dom_other, but please double check. This lockless call should be made
> clear in the LSM hook. It's OK to not lock the socket before
> security_unix_find() (1) because no LSM might implement and (2) they
> might not need to lock the socket (e.g. if the caller is not sandboxed).
>
> The updated code should look something like this:
>
> unix_state_unlock(other);
> if (unlikely(sock_flag(other, SOCK_DEAD) || !other->sk_socket)) {
> unix_state_unlock(other);
> return 0;
> }
>
> dom_other = landlock_cred(other->sk_socket->file->f_cred)->domain;
> unix_state_unlock(other);
Thank you for spotting the locking concern!
@anyone from netdev, could you please advise on the correct locking
approach here?
* Do we need ot check SOCK_DEAD?
You are saying that we need to do that, but it's not clear to me
why.
If you look at the places where unix_find_other() is called in
af_unix.c, then you'll find that all of them check for SOCK_DEAD and
then restart from unix_find_other() if they do actually discover
that the socket is dead. I think that this is catching this race
condition scenario:
* a server socket exists and is alive
* A client connects: af_unix.c's unix_stream_connect() calls
unix_find_other() and finds the server socket...
* (Concurrently): The server closes the socket and enters
unix_release_sock(). This function:
1. disassociates the server sock from the named socket inode
number in the hash table (=> future unix_find_other() calls
will fail).
2. calls sock_orphan(), which sets SOCK_DEAD.
* ...(client connection resuming): unix_stream_connect() continues,
grabs the unix_state_lock(), which apparently protects everything
here, checks that the socket is not dead - and discovers that it
IS suddenly dead. This was not supposed to happen. The code
recovers from that by retrying everything starting with the
unix_find_other() call. From unix_release_sock(), we know that
the inode is not associated with the sock any more -- so the
unix_find_socket_by_inode() call should be failing on the next
attempt.
(This works with unix_dgram_connect() and unix_dgram_sendmsg() as
well.)
The comments next to the SOCK_DEAD checks are also suggesting this.
* What lock to use
I am having trouble reasoning about what lock is used for what in
this code.
Is it possible that the lock protecting ->sk_socket is the
->sk_callback_lock, not the unix_state_lock()? The only callers to
sk_set_socket are either sock_orphan/sock_graft (both grabbing
sk_callback_lock), or they are creating new struct sock objects that
they own exclusively, and don't need locks yet.
Admittedly, in af_unix.c, sock_orphan() and sock_graft() only get
called in contexts where the unix_state_lock() is held, so it would
probably work as well to lock that, but it is maybe a more
fine-grained approach to use sk_callback_lock?
So... how about a scheme where we only check for ->sk_socket not being
NULL:
read_lock_bh(&other->sk_callback_lock);
struct sock *other_sk = other->sk_socket;
if (!other_sk) {
read_unlock_bh(&other->sk_callback_lock);
return 0;
}
/* XXX double check whether we need a lock here too */
struct file *file = other_sk->file;
if (!other_file) {
read_unlock_bh(&other->sk_callback_lock);
return 0;
}
read_unlock_bh(&other->sk_callback_lock);
If this fails, that would in my understanding also be because the
socket has died after the path lookup. We'd then return 0 (success),
because we know that the surrounding SOCK_DEAD logic will repeat
everything starting from the path lookup operation (this time likely
failing with ECONNREFUSED, but maybe also with a success, if another
server process was quick enough).
Does this sound reasonable?
–Günther
^ permalink raw reply
* Re: [PATCH v6] lsm: Add LSM hook security_unix_find
From: Günther Noack @ 2026-02-20 15:49 UTC (permalink / raw)
To: Justin Suess
Cc: brauner, demiobenour, fahimitahera, hi, horms, ivanov.mikhail1,
jannh, jmorris, john.johansen, konstantin.meskhidze,
linux-security-module, m, matthieu, mic, netdev, paul,
samasth.norway.ananda, serge, viro
In-Reply-To: <20260219200459.1474232-1-utilityemal77@gmail.com>
Hello!
On Thu, Feb 19, 2026 at 03:04:59PM -0500, Justin Suess wrote:
> diff --git a/security/security.c b/security/security.c
> index 67af9228c4e9..c73196b8db4b 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -4731,6 +4731,26 @@ int security_mptcp_add_subflow(struct sock *sk, struct sock *ssk)
>
> #endif /* CONFIG_SECURITY_NETWORK */
>
> +#if defined(CONFIG_SECURITY_NETWORK) && defined(CONFIG_SECURITY_PATH)
> +/**
> + * security_unix_find() - Check if a named AF_UNIX socket can connect
> + * @path: path of the socket being connected to
> + * @other: peer sock
> + * @flags: flags associated with the socket
> + *
> + * This hook is called to check permissions before connecting to a named
> + * AF_UNIX socket.
Nit: Could we please insert a sentence about locking here?
Something like:
The caller holds no locks on @other.
(Originally brought up by Mickaël in
https://lore.kernel.org/all/20260217.lievaS8eeng8@digikod.net/)
Thanks,
–Günther
^ permalink raw reply
* [PATCH] samples/landlock: Bump ABI version to 8
From: Günther Noack @ 2026-02-20 16:06 UTC (permalink / raw)
To: Mickaël Salaün; +Cc: linux-security-module, Günther Noack
The sample tool should print a warning if it is not running on a
kernel that provides the newest Landlock ABI version.
Link: https://lore.kernel.org/all/20260218.ufao5Vaefa2u@digikod.net/
Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
samples/landlock/sandboxer.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index e7af02f98208..9f21088c0855 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -299,7 +299,7 @@ static bool check_ruleset_scope(const char *const env_var,
/* clang-format on */
-#define LANDLOCK_ABI_LAST 7
+#define LANDLOCK_ABI_LAST 8
#define XSTR(s) #s
#define STR(s) XSTR(s)
@@ -436,7 +436,8 @@ int main(const int argc, char *const argv[], char *const *const envp)
/* Removes LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON for ABI < 7 */
supported_restrict_flags &=
~LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON;
-
+ __attribute__((fallthrough));
+ case 7:
/* Must be printed for any ABI < LANDLOCK_ABI_LAST. */
fprintf(stderr,
"Hint: You should update the running kernel "
--
2.52.0
^ permalink raw reply related
* Re: [PATCH v5 3/9] samples/landlock: Add support for named UNIX domain socket restrictions
From: Günther Noack @ 2026-02-20 16:08 UTC (permalink / raw)
To: Mickaël Salaün
Cc: John Johansen, Justin Suess, linux-security-module, Tingmao Wang,
Samasth Norway Ananda, Matthieu Buffet, Mikhail Ivanov,
konstantin.meskhidze, Demi Marie Obenour, Alyssa Ross, Jann Horn,
Tahera Fahimi
In-Reply-To: <20260218.ufao5Vaefa2u@digikod.net>
On Wed, Feb 18, 2026 at 10:37:31AM +0100, Mickaël Salaün wrote:
> On Sun, Feb 15, 2026 at 11:51:51AM +0100, Günther Noack wrote:
> > @@ -444,6 +446,13 @@ int main(const int argc, char *const argv[], char *const *const envp)
> > "provided by ABI version %d (instead of %d).\n",
> > LANDLOCK_ABI_LAST, abi);
> > __attribute__((fallthrough));
> > + case 7:
> > + __attribute__((fallthrough));
>
> The current code should print the hint when ABI <= 7. Please send a
> dedicated patch to fix the TSYNC-related changes.
Good catch, thanks! I sent a follow-up.
https://lore.kernel.org/all/20260220160627.53913-1-gnoack3000@gmail.com/
–Günther
^ permalink raw reply
* Re: [PATCH v5 4/9] landlock/selftests: Test LANDLOCK_ACCESS_FS_RESOLVE_UNIX
From: Günther Noack @ 2026-02-20 16:27 UTC (permalink / raw)
To: Mickaël Salaün
Cc: John Johansen, Justin Suess, Tingmao Wang, linux-security-module,
Samasth Norway Ananda, Matthieu Buffet, Mikhail Ivanov,
konstantin.meskhidze, Demi Marie Obenour, Alyssa Ross, Jann Horn,
Tahera Fahimi
In-Reply-To: <20260218.aser1cu7Aewi@digikod.net>
On Wed, Feb 18, 2026 at 08:11:26PM +0100, Mickaël Salaün wrote:
> On Sun, Feb 15, 2026 at 11:51:52AM +0100, Günther Noack wrote:
> > --- a/tools/testing/selftests/landlock/fs_test.c
> > +++ b/tools/testing/selftests/landlock/fs_test.c
> > + strncpy(addr.sun_path, path, sizeof(addr.sun_path));
>
> fs_test.c: In function ‘set_up_named_unix_server’:
> fs_test.c:4125:9: error: ‘strncpy’ specified bound 108 equals destination size [-Werror=stringop-truncation]
> 4125 | strncpy(addr.sun_path, path, sizeof(addr.sun_path));
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> We should also ASSERT the result to make sure path's length is not too big.
Fair enough, will do, because it's less confusing.
(FWIW though, I think Linux can technically deal with a sun_path that
does not end in a NUL byte. See the long comment in unix_mkname_bsd().
But that's a Linux peculiarity.)
–Günther
^ permalink raw reply
* Re: [PATCH v5 4/9] landlock/selftests: Test LANDLOCK_ACCESS_FS_RESOLVE_UNIX
From: Günther Noack @ 2026-02-20 17:04 UTC (permalink / raw)
To: Mickaël Salaün
Cc: John Johansen, Justin Suess, Tingmao Wang, linux-security-module,
Samasth Norway Ananda, Matthieu Buffet, Mikhail Ivanov,
konstantin.meskhidze, Demi Marie Obenour, Alyssa Ross, Jann Horn,
Tahera Fahimi
In-Reply-To: <20260220.5f431119d04a@gnoack.org>
On Fri, Feb 20, 2026 at 05:27:52PM +0100, Günther Noack wrote:
> On Wed, Feb 18, 2026 at 08:11:26PM +0100, Mickaël Salaün wrote:
> > On Sun, Feb 15, 2026 at 11:51:52AM +0100, Günther Noack wrote:
> > > --- a/tools/testing/selftests/landlock/fs_test.c
> > > +++ b/tools/testing/selftests/landlock/fs_test.c
>
> > > + strncpy(addr.sun_path, path, sizeof(addr.sun_path));
> >
> > fs_test.c: In function ‘set_up_named_unix_server’:
> > fs_test.c:4125:9: error: ‘strncpy’ specified bound 108 equals destination size [-Werror=stringop-truncation]
> > 4125 | strncpy(addr.sun_path, path, sizeof(addr.sun_path));
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > We should also ASSERT the result to make sure path's length is not too big.
>
> Fair enough, will do, because it's less confusing.
>
> (FWIW though, I think Linux can technically deal with a sun_path that
> does not end in a NUL byte. See the long comment in unix_mkname_bsd().
> But that's a Linux peculiarity.)
FYI, before the question comes up why I didn't use strscpy: We don't
have that library in these userspace tests, so it is now:
struct sockaddr_un addr = {
.sun_family = AF_UNIX,
};
ASSERT_LT(strlen(path), sizeof(addr.sun_path));
strncpy(addr.sun_path, path, sizeof(addr.sun_path)-1);
–Günther
^ permalink raw reply
* Re: [PATCH v15 9/9] rust: page: add `from_raw()`
From: Miguel Ojeda @ 2026-02-20 17:33 UTC (permalink / raw)
To: Andreas Hindborg, Tamir Duberstein, Benno Lossin
Cc: Miguel Ojeda, Gary Guo, Björn Roy Baron, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Igor Korotin, Daniel Almeida,
Lorenzo Stoakes, Liam R. Howlett, Viresh Kumar, Nishanth Menon,
Stephen Boyd, Bjorn Helgaas, Krzysztof Wilczyński,
Boqun Feng, linux-kernel, rust-for-linux, linux-block,
linux-security-module, dri-devel, linux-fsdevel, linux-mm,
linux-pm, linux-pci
In-Reply-To: <20260220-unique-ref-v15-9-893ed86b06cc@kernel.org>
On Fri, Feb 20, 2026 at 10:52 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
> + /// Create a `&Page` from a raw `struct page` pointer
Please end sentences with a period.
> + // SAFETY: By function safety requirements, ptr is not null and is
Please use Markdown in comments: `ptr`.
> + /// `ptr` must be valid for use as a reference for the duration of `'a`.
Since we will likely try to starting introducing at least a subset of
the Safety Standard soon, we should try to use standard terms.
So I think this "valid for use as a reference" is not an established
one, no? Isn't "convertible to a shared reference" the official term?
https://doc.rust-lang.org/std/ptr/index.html#pointer-to-reference-conversion
In fact, I see `as_ref_unchecked()` and `as_mut_unchecked()` just got
stabilized for 1.95.0, so we should probably starting using those were
applicable as we bump the minimum, but we should probably use already
a similar wording as the standard library for the safety section and
the comment:
"`ptr` must be [convertible to a reference](...)."
where the term is a link to that section. Cc'ing Benno.
I have created a (future) issue for that:
https://github.com/Rust-for-Linux/linux/issues/1225
Cc'ing Tamir since this is close to the cast work, so it may interest
him as well.
Cheers,
Miguel
^ permalink raw reply
* Re: [PATCH v15 9/9] rust: page: add `from_raw()`
From: Tamir Duberstein @ 2026-02-20 17:50 UTC (permalink / raw)
To: Miguel Ojeda
Cc: Andreas Hindborg, Benno Lossin, Miguel Ojeda, Gary Guo,
Björn Roy Baron, Alice Ryhl, Trevor Gross, Danilo Krummrich,
Greg Kroah-Hartman, Dave Ertman, Ira Weiny, Leon Romanovsky,
Paul Moore, Serge Hallyn, Rafael J. Wysocki, David Airlie,
Simona Vetter, Alexander Viro, Christian Brauner, Jan Kara,
Igor Korotin, Daniel Almeida, Lorenzo Stoakes, Liam R. Howlett,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Boqun Feng, linux-kernel,
rust-for-linux, linux-block, linux-security-module, dri-devel,
linux-fsdevel, linux-mm, linux-pm, linux-pci
In-Reply-To: <CANiq72myc+tCEHm0WtZspZHWwsSzvesxsmUvk31=GCdUN_zVNA@mail.gmail.com>
On Fri, Feb 20, 2026 at 12:34 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> On Fri, Feb 20, 2026 at 10:52 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
> >
> > + /// Create a `&Page` from a raw `struct page` pointer
>
> Please end sentences with a period.
>
> > + // SAFETY: By function safety requirements, ptr is not null and is
>
> Please use Markdown in comments: `ptr`.
>
> > + /// `ptr` must be valid for use as a reference for the duration of `'a`.
>
> Since we will likely try to starting introducing at least a subset of
> the Safety Standard soon, we should try to use standard terms.
>
> So I think this "valid for use as a reference" is not an established
> one, no? Isn't "convertible to a shared reference" the official term?
>
> https://doc.rust-lang.org/std/ptr/index.html#pointer-to-reference-conversion
>
> In fact, I see `as_ref_unchecked()` and `as_mut_unchecked()` just got
> stabilized for 1.95.0, so we should probably starting using those were
> applicable as we bump the minimum, but we should probably use already
> a similar wording as the standard library for the safety section and
> the comment:
>
> "`ptr` must be [convertible to a reference](...)."
>
> where the term is a link to that section. Cc'ing Benno.
>
> I have created a (future) issue for that:
>
> https://github.com/Rust-for-Linux/linux/issues/1225
>
> Cc'ing Tamir since this is close to the cast work, so it may interest
> him as well.
Thanks Miguel -- FWIW there's no current cast work on my plate, I
believe everything was merged except for provenance which was a bit
too hard to work with given MSRV.
^ permalink raw reply
* Re: [PATCH v9 01/11] KEYS: trusted: Use get_random-fallback for TPM
From: Mimi Zohar @ 2026-02-20 18:04 UTC (permalink / raw)
To: Jarkko Sakkinen, linux-integrity, Chris Fenner, Jonathan McDowell
Cc: Eric Biggers, James Bottomley, David Howells, Paul Moore,
James Morris, Serge E. Hallyn, open list:KEYS-TRUSTED,
open list:SECURITY SUBSYSTEM, open list, Roberto Sassu
In-Reply-To: <20260125192526.782202-2-jarkko@kernel.org>
[Cc: Chris Fenner, Jonathan McDowell, Roberto]
On Sun, 2026-01-25 at 21:25 +0200, Jarkko Sakkinen wrote:
> 1. tpm2_get_random() is costly when TCG_TPM2_HMAC is enabled and thus its
> use should be pooled rather than directly used. This both reduces
> latency and improves its predictability.
If the concern is the latency of encrypting the bus session, please remember
that:
- Not all environments expose the TPM bus to sniffing.
- The current TPM trusted keys design is based on TPM RNG, but already allows it
to be replaced with the kernel RNG via the "trusted_rng=kernel" boot command
line option.
- The proposed patch removes that possibility for no reason.
Mimi & Elaine
^ permalink raw reply
* Re: [PATCH v9 01/11] KEYS: trusted: Use get_random-fallback for TPM
From: Chris Fenner @ 2026-02-20 18:30 UTC (permalink / raw)
To: Mimi Zohar
Cc: Jarkko Sakkinen, linux-integrity, Jonathan McDowell, Eric Biggers,
James Bottomley, David Howells, Paul Moore, James Morris,
Serge E. Hallyn, open list:KEYS-TRUSTED,
open list:SECURITY SUBSYSTEM, open list, Roberto Sassu
In-Reply-To: <06a08cbbe47111a1795e5dcd42fb8cc4be643a72.camel@linux.ibm.com>
My conclusion about TCG_TPM2_HMAC after [1] and [2] was that
TPM2_TCG_HMAC doesn't (or didn't at the time) actually solve the
threat model it claims to (active interposer adversaries), while
dramatically increasing the cost of many kernel TPM activities beyond
the amount that would have been required to just solve for
passive/bus-sniffer interposer adversaries. The added symmetric crypto
required to secure a TPM transaction is almost not noticeable; the big
performance problem is the re-bootstrapping of the session with ECDH
for every command.
My primary concern at that time was, essentially, that TCG_TPM2_HMAC
punts on checking that the key that was used to secure the session was
actually resident in a real TPM and not just an interposer adversary.
I wrote up my understanding at
https://www.dlp.rip/decorative-cryptography, for anyone who wants a
long-form opinionated take :).
Unless I'm wrong, or TCG_TPM2_HMAC has changed dramatically since
August, I don't think "TPM2_TCG_HMAC makes this too costly" is a
compelling reason to make a security decision. (There could be other
reasons to make choices about whether to use the TPM as a source of
randomness in the kernel! This just isn't one IMHO.)
The version of TCG_TPM2_HMAC that I'd like to see someday would be one
that fully admits that its threat model is only passive interposers,
and sets up one session upon startup and ContextSaves/ContextLoads it
back into the TPM as needed in order to secure parameter encryption
for e.g., GetRandom() and Unseal() calls.
[1]: https://lore.kernel.org/linux-integrity/CAMigqh2nwuRRxaLyOJ+QaTJ+XGmkQj=rMj5K9GP1bCcXp2OsBQ@mail.gmail.com/
[2]: https://lore.kernel.org/linux-integrity/20250825203223.629515-1-jarkko@kernel.org/
Thanks
Chris
On Fri, Feb 20, 2026 at 10:04 AM Mimi Zohar <zohar@linux.ibm.com> wrote:
>
> [Cc: Chris Fenner, Jonathan McDowell, Roberto]
>
> On Sun, 2026-01-25 at 21:25 +0200, Jarkko Sakkinen wrote:
> > 1. tpm2_get_random() is costly when TCG_TPM2_HMAC is enabled and thus its
> > use should be pooled rather than directly used. This both reduces
> > latency and improves its predictability.
>
> If the concern is the latency of encrypting the bus session, please remember
> that:
>
> - Not all environments expose the TPM bus to sniffing.
> - The current TPM trusted keys design is based on TPM RNG, but already allows it
> to be replaced with the kernel RNG via the "trusted_rng=kernel" boot command
> line option.
> - The proposed patch removes that possibility for no reason.
>
> Mimi & Elaine
>
>
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