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Currently, the driver's device private data is allocated and initialized
from driver core code called from bus abstractions after the driver's
probe() callback returned the corresponding initializer.
Similarly, the driver's device private data is dropped within the
remove() callback of bus abstractions after calling the remove()
callback of the corresponding driver.
However, commit 6f61a2637abe ("rust: device: introduce
Device::drvdata()") introduced an accessor for the driver's device
private data for a Device<Bound>, i.e. a device that is currently bound
to a driver.
Obviously, this is in conflict with dropping the driver's device private
data in remove(), since a device can not be considered to be fully
unbound after remove() has finished:
We also have to consider registrations guarded by devres - such as IRQ
or class device registrations - which are torn down after remove() in
devres_release_all().
Thus, it can happen that, for instance, a class device or IRQ callback
still calls Device::drvdata(), which then runs concurrently to remove()
(which sets dev->driver_data to NULL and drops the driver's device
private data), before devres_release_all() started to tear down the
corresponding registration. This is because devres guarded registrations
can, as expected, access the corresponding Device<Bound> that defines
their scope.
In C it simply is the driver's responsibility to ensure that its device
private data is freed after e.g. an IRQ registration is unregistered.
Typically, C drivers achieve this by allocating their device private data
with e.g. devm_kzalloc() before doing anything else, i.e. before e.g.
registering an IRQ with devm_request_threaded_irq(), relying on the
reverse order cleanup of devres.
Technically, we could do something similar in Rust. However, the
resulting code would be pretty messy:
In Rust we have to differentiate between allocated but uninitialized
memory and initialized memory in the type system. Thus, we would need to
somehow keep track of whether the driver's device private data object
has been initialized (i.e. probe() was successful and returned a valid
initializer for this memory) and conditionally call the destructor of
the corresponding object when it is freed.
This is because we'd need to allocate and register the memory of the
driver's device private data *before* it is initialized by the
initializer returned by the driver's probe() callback, because the
driver could already register devres guarded registrations within
probe() outside of the driver's device private data initializer.
Luckily there is a much simpler solution: Instead of dropping the
driver's device private data at the end of remove(), we just drop it
after the device has been fully unbound, i.e. after all devres callbacks
have been processed.
For this, we introduce a new post_unbind() callback private to the
driver-core, i.e. the callback is neither exposed to drivers, nor to bus
abstractions.
This way, the driver-core code can simply continue to conditionally
allocate the memory for the driver's device private data when the
driver's initializer is returned from probe() - no change needed - and
drop it when the driver-core code receives the post_unbind() callback.
Closes: https://lore.kernel.org/all/DEZMS6Y4A7XE.XE7EUBT5SJFJ@kernel.org/
Fixes: 6f61a2637abe ("rust: device: introduce Device::drvdata()")
Acked-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20260107103511.570525-7-dakr@kernel.org
[ Remove #ifdef CONFIG_RUST, rename post_unbind() to post_unbind_rust().
- Danilo]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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Add an associated type DriverData to the DriverLayout trait indicating
the type of the driver's device private data.
Acked-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20260107103511.570525-6-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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Add an associated const DEVICE_DRIVER_OFFSET to the DriverLayout trait
indicating the offset of the embedded struct device_driver within
Self::DriverType, i.e. the specific driver structs, such as struct
pci_driver or struct platform_driver.
Acked-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20260107103511.570525-5-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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The DriverLayout trait describes the layout of a specific driver
structure, such as `struct pci_driver` or `struct platform_driver`.
In a first step, this replaces the associated type RegType of the
RegistrationOps with the DriverLayout::DriverType associated type.
Acked-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20260107103511.570525-4-dakr@kernel.org
[ Rename driver::Driver to driver::DriverLayout, as it represents the
layout of a driver structure rather than the driver structure itself.
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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We must not drop the device private data on shutdown(); none of the
registrations attached to devres that might access the device private
data are released before shutdown() is called.
Hence, freeing the device private data on shutdown() can cause UAF bugs.
Fixes: 57c5bd9aee94 ("rust: i2c: add basic I2C device and driver abstractions")
Acked-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20260107103511.570525-2-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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The rust-next tree contains commit:
3b83f5d5e78a ("rust: replace `CStr` with `core::ffi::CStr`")
which, when merged together with commits:
57c5bd9aee94 ("rust: i2c: add basic I2C device and driver abstractions")
f3cc26a417b7 ("rust: i2c: add manual I2C device creation abstractions")
from this tree (driver-core), produces errors like the following:
error[E0599]: no method named `len_with_nul` found for reference `&'static ffi::CStr` in the current scope
--> rust/kernel/i2c.rs:48:16
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48 | id.len_with_nul() <= Self::I2C_NAME_SIZE,
| ^^^^^^^^^^^^ method not found in `&CStr`
error[E0599]: no method named `as_bytes_with_nul` found for reference `&'static ffi::CStr` in the current scope
--> rust/kernel/i2c.rs:51:22
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51 | let src = id.as_bytes_with_nul();
| ^^^^^^^^^^^^^^^^^
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help: there is a method `to_bytes_with_nul` with a similar name
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51 | let src = id.to_bytes_with_nul();
| ~~~~~~~~~~~~~~~~~
which were detected in linux-next by Stephen [1].
The `i2c` code can be independently prepared to be ready for the change,
thus do so.
The change is similar to the one done by Tamir in commit 657403637f7d
("rust: acpi: use `core::ffi::CStr` method names").
Link: https://lore.kernel.org/all/20251120181111.65ce75a0@canb.auug.org.au/ [1]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://patch.msgid.link/20251123163536.1771801-1-ojeda@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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Implement the `AsBusDevice` trait for converting a `Device` reference to a
bus device reference for all bus devices.
The `AsBusDevice` trait allows abstractions to provide the bus device in
class device callbacks. It must not be used by drivers and is intended for
bus and class device abstractions only.
Signed-off-by: Markus Probst <markus.probst@posteo.de>
Link: https://patch.msgid.link/20251027200547.1038967-2-markus.probst@posteo.de
[ * Remove unused import.
* Change visibility of AsBusDevice to public.
* Fix build for USB.
* Add impl for I2cClient.
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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In addition to the basic I2C device support, add rust abstractions
upon `i2c_new_client_device`/`i2c_unregister_device` C functions.
Implement the core abstractions needed for manual creation/deletion
of I2C devices, including:
* `i2c::Registration` — a NonNull pointer created by the function
`i2c_new_client_device`
* `i2c::I2cAdapter` — a ref counted wrapper around `struct i2c_adapter`
* `i2c::I2cBoardInfo` — a safe wrapper around `struct i2c_board_info`
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20251116162154.171493-1-igor.korotin.linux@gmail.com
[ Remove unnecessary safety comment. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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Implement the core abstractions needed for I2C drivers, including:
* `i2c::Driver` — the trait drivers must implement, including `probe`
* `i2c::I2cClient` — a safe wrapper around `struct i2c_client`
* `i2c::Adapter` — implements `driver::RegistrationOps` to hook into the
generic `driver::Registration` machinery
* `i2c::DeviceId` — a `RawDeviceIdIndex` implementation for I2C device IDs
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20251116162144.171469-1-igor.korotin.linux@gmail.com
[ Remove unnecessary safety comment; fix rustdoc `Device` -> `I2cClient`.
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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