mirror of
https://github.com/torvalds/linux.git
synced 2025-10-31 08:38:45 +02:00
046c56178a
Update the import of `AlwaysRefCounted` in `cred.rs` to use `sync::aref` instead of `types`. This is part of the ongoing effort to move `ARef` and `AlwaysRefCounted` to the `sync` module for better modularity. Suggested-by: Benno Lossin <lossin@kernel.org> Link: https://github.com/Rust-for-Linux/linux/issues/1173 Signed-off-by: Shankari Anand <shankari.ak0208@gmail.com> Acked-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Benno Lossin <lossin@kernel.org> Reviewed-by: Alice Ryhl <aliceryhl@google.com> [PM: subj tweak] Signed-off-by: Paul Moore <paul@paul-moore.com>
86 lines
3.3 KiB
Rust
86 lines
3.3 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
|
|
|
|
// Copyright (C) 2024 Google LLC.
|
|
|
|
//! Credentials management.
|
|
//!
|
|
//! C header: [`include/linux/cred.h`](srctree/include/linux/cred.h).
|
|
//!
|
|
//! Reference: <https://www.kernel.org/doc/html/latest/security/credentials.html>
|
|
|
|
use crate::{bindings, sync::aref::AlwaysRefCounted, task::Kuid, types::Opaque};
|
|
|
|
/// Wraps the kernel's `struct cred`.
|
|
///
|
|
/// Credentials are used for various security checks in the kernel.
|
|
///
|
|
/// Most fields of credentials are immutable. When things have their credentials changed, that
|
|
/// happens by replacing the credential instead of changing an existing credential. See the [kernel
|
|
/// documentation][ref] for more info on this.
|
|
///
|
|
/// # Invariants
|
|
///
|
|
/// Instances of this type are always ref-counted, that is, a call to `get_cred` ensures that the
|
|
/// allocation remains valid at least until the matching call to `put_cred`.
|
|
///
|
|
/// [ref]: https://www.kernel.org/doc/html/latest/security/credentials.html
|
|
#[repr(transparent)]
|
|
pub struct Credential(Opaque<bindings::cred>);
|
|
|
|
// SAFETY:
|
|
// - `Credential::dec_ref` can be called from any thread.
|
|
// - It is okay to send ownership of `Credential` across thread boundaries.
|
|
unsafe impl Send for Credential {}
|
|
|
|
// SAFETY: It's OK to access `Credential` through shared references from other threads because
|
|
// we're either accessing properties that don't change or that are properly synchronised by C code.
|
|
unsafe impl Sync for Credential {}
|
|
|
|
impl Credential {
|
|
/// Creates a reference to a [`Credential`] from a valid pointer.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// The caller must ensure that `ptr` is valid and remains valid for the lifetime of the
|
|
/// returned [`Credential`] reference.
|
|
#[inline]
|
|
pub unsafe fn from_ptr<'a>(ptr: *const bindings::cred) -> &'a Credential {
|
|
// SAFETY: The safety requirements guarantee the validity of the dereference, while the
|
|
// `Credential` type being transparent makes the cast ok.
|
|
unsafe { &*ptr.cast() }
|
|
}
|
|
|
|
/// Get the id for this security context.
|
|
#[inline]
|
|
pub fn get_secid(&self) -> u32 {
|
|
let mut secid = 0;
|
|
// SAFETY: The invariants of this type ensures that the pointer is valid.
|
|
unsafe { bindings::security_cred_getsecid(self.0.get(), &mut secid) };
|
|
secid
|
|
}
|
|
|
|
/// Returns the effective UID of the given credential.
|
|
#[inline]
|
|
pub fn euid(&self) -> Kuid {
|
|
// SAFETY: By the type invariant, we know that `self.0` is valid. Furthermore, the `euid`
|
|
// field of a credential is never changed after initialization, so there is no potential
|
|
// for data races.
|
|
Kuid::from_raw(unsafe { (*self.0.get()).euid })
|
|
}
|
|
}
|
|
|
|
// SAFETY: The type invariants guarantee that `Credential` is always ref-counted.
|
|
unsafe impl AlwaysRefCounted for Credential {
|
|
#[inline]
|
|
fn inc_ref(&self) {
|
|
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
|
|
unsafe { bindings::get_cred(self.0.get()) };
|
|
}
|
|
|
|
#[inline]
|
|
unsafe fn dec_ref(obj: core::ptr::NonNull<Credential>) {
|
|
// SAFETY: The safety requirements guarantee that the refcount is nonzero. The cast is okay
|
|
// because `Credential` has the same representation as `struct cred`.
|
|
unsafe { bindings::put_cred(obj.cast().as_ptr()) };
|
|
}
|
|
}
|