On Wed, Nov 29, 2023 at 01:12:17PM +0000, Alice Ryhl wrote:
> Adds a wrapper around `kuid_t` called `Kuid`. This allows us to define
> various operations on kuids such as equality and current_euid. It also
> lets us provide conversions from kuid into userspace values.
>
> Rust Binder needs these operations because it needs to compare kuids for
> equality, and it needs to tell userspace about the pid and uid of
> incoming transactions.
>
> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> ---
> rust/bindings/bindings_helper.h | 1 +
> rust/helpers.c | 45 ++++++++++++++++++++++++++
> rust/kernel/cred.rs | 5 +--
> rust/kernel/task.rs | 71 ++++++++++++++++++++++++++++++++++++++++-
> 4 files changed, 119 insertions(+), 3 deletions(-)
>
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 81b13a953eae..700f01840188 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -11,6 +11,7 @@
> #include <linux/errname.h>
> #include <linux/file.h>
> #include <linux/fs.h>
> +#include <linux/pid_namespace.h>
> #include <linux/security.h>
> #include <linux/slab.h>
> #include <linux/refcount.h>
> diff --git a/rust/helpers.c b/rust/helpers.c
> index fd633d9db79a..58e3a9dff349 100644
> --- a/rust/helpers.c
> +++ b/rust/helpers.c
> @@ -142,6 +142,51 @@ void rust_helper_put_task_struct(struct task_struct *t)
> }
> EXPORT_SYMBOL_GPL(rust_helper_put_task_struct);
>
> +kuid_t rust_helper_task_uid(struct task_struct *task)
> +{
> + return task_uid(task);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_task_uid);
> +
> +kuid_t rust_helper_task_euid(struct task_struct *task)
> +{
> + return task_euid(task);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_task_euid);
> +
> +#ifndef CONFIG_USER_NS
> +uid_t rust_helper_from_kuid(struct user_namespace *to, kuid_t uid)
> +{
> + return from_kuid(to, uid);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_from_kuid);
> +#endif /* CONFIG_USER_NS */
> +
> +bool rust_helper_uid_eq(kuid_t left, kuid_t right)
> +{
> + return uid_eq(left, right);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_uid_eq);
> +
> +kuid_t rust_helper_current_euid(void)
> +{
> + return current_euid();
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_current_euid);
> +
> +struct user_namespace *rust_helper_current_user_ns(void)
> +{
> + return current_user_ns();
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_current_user_ns);
> +
> +pid_t rust_helper_task_tgid_nr_ns(struct task_struct *tsk,
> + struct pid_namespace *ns)
> +{
> + return task_tgid_nr_ns(tsk, ns);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_task_tgid_nr_ns);
I'm a bit puzzled by all these rust_helper_*() calls. Can you explain
why they are needed? Because they are/can be static inlines and that
somehow doesn't work?
> +
> struct kunit *rust_helper_kunit_get_current_test(void)
> {
> return kunit_get_current_test();
> diff --git a/rust/kernel/cred.rs b/rust/kernel/cred.rs
> index 3794937b5294..fbc749788bfa 100644
> --- a/rust/kernel/cred.rs
> +++ b/rust/kernel/cred.rs
> @@ -8,6 +8,7 @@
>
> use crate::{
> bindings,
> + task::Kuid,
> types::{AlwaysRefCounted, Opaque},
> };
>
> @@ -52,9 +53,9 @@ pub fn get_secid(&self) -> u32 {
> }
>
> /// Returns the effective UID of the given credential.
> - pub fn euid(&self) -> bindings::kuid_t {
> + pub fn euid(&self) -> Kuid {
> // SAFETY: By the type invariant, we know that `self.0` is valid.
> - unsafe { (*self.0.get()).euid }
> + Kuid::from_raw(unsafe { (*self.0.get()).euid })
> }
> }
>
> diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
> index b2299bc7ac1f..1a27b968a907 100644
> --- a/rust/kernel/task.rs
> +++ b/rust/kernel/task.rs
> @@ -5,7 +5,12 @@
> //! C header: [`include/linux/sched.h`](../../../../include/linux/sched.h).
>
> use crate::{bindings, types::Opaque};
> -use core::{marker::PhantomData, ops::Deref, ptr};
> +use core::{
> + cmp::{Eq, PartialEq},
> + marker::PhantomData,
> + ops::Deref,
> + ptr,
> +};
>
> /// Returns the currently running task.
> #[macro_export]
> @@ -78,6 +83,12 @@ unsafe impl Sync for Task {}
> /// The type of process identifiers (PIDs).
> type Pid = bindings::pid_t;
>
> +/// The type of user identifiers (UIDs).
> +#[derive(Copy, Clone)]
> +pub struct Kuid {
> + kuid: bindings::kuid_t,
> +}
> +
> impl Task {
> /// Returns a task reference for the currently executing task/thread.
> ///
> @@ -132,12 +143,34 @@ pub fn pid(&self) -> Pid {
> unsafe { *ptr::addr_of!((*self.0.get()).pid) }
> }
>
> + /// Returns the UID of the given task.
> + pub fn uid(&self) -> Kuid {
> + // SAFETY: By the type invariant, we know that `self.0` is valid.
> + Kuid::from_raw(unsafe { bindings::task_uid(self.0.get()) })
> + }
> +
> + /// Returns the effective UID of the given task.
> + pub fn euid(&self) -> Kuid {
> + // SAFETY: By the type invariant, we know that `self.0` is valid.
> + Kuid::from_raw(unsafe { bindings::task_euid(self.0.get()) })
> + }
> +
> /// Determines whether the given task has pending signals.
> pub fn signal_pending(&self) -> bool {
> // SAFETY: By the type invariant, we know that `self.0` is valid.
> unsafe { bindings::signal_pending(self.0.get()) != 0 }
> }
>
> + /// Returns the given task's pid in the current pid namespace.
> + pub fn pid_in_current_ns(&self) -> Pid {
> + // SAFETY: We know that `self.0.get()` is valid by the type invariant. The rest is just FFI
> + // calls.
> + unsafe {
> + let namespace = bindings::task_active_pid_ns(bindings::get_current());
> + bindings::task_tgid_nr_ns(self.0.get(), namespace)
> + }
> + }
> +
> /// Wakes up the task.
> pub fn wake_up(&self) {
> // SAFETY: By the type invariant, we know that `self.0.get()` is non-null and valid.
> @@ -147,6 +180,42 @@ pub fn wake_up(&self) {
> }
> }
>
> +impl Kuid {
> + /// Get the current euid.
> + pub fn current_euid() -> Kuid {
> + // SAFETY: Just an FFI call.
> + Self {
> + kuid: unsafe { bindings::current_euid() },
> + }
> + }
> +
> + /// Create a `Kuid` given the raw C type.
> + pub fn from_raw(kuid: bindings::kuid_t) -> Self {
> + Self { kuid }
> + }
> +
> + /// Turn this kuid into the raw C type.
> + pub fn into_raw(self) -> bindings::kuid_t {
> + self.kuid
> + }
> +
> + /// Converts this kernel UID into a UID that userspace understands. Uses the namespace of the
> + /// current task.
> + pub fn into_uid_in_current_ns(self) -> bindings::uid_t {
Hm, I wouldn't special-case this. Just expose from_kuid() and let it
take a namespace argument, no? You don't need to provide bindings for
namespaces ofc.
> + // SAFETY: Just an FFI call.
> + unsafe { bindings::from_kuid(bindings::current_user_ns(), self.kuid) }
> + }
> +}
> +
> +impl PartialEq for Kuid {
> + fn eq(&self, other: &Kuid) -> bool {
> + // SAFETY: Just an FFI call.
> + unsafe { bindings::uid_eq(self.kuid, other.kuid) }
> + }
> +}
> +
> +impl Eq for Kuid {}
Do you need that?
> +
> // SAFETY: The type invariants guarantee that `Task` is always ref-counted.
> unsafe impl crate::types::AlwaysRefCounted for Task {
> fn inc_ref(&self) {
>
> --
> 2.43.0.rc1.413.gea7ed67945-goog
>
