[PATCH v5 2/2] cred: delete task_euid()
From: Alice Ryhl <aliceryhl@google.com>
Date: 2026-07-03 06:57:15
Also in:
linux-doc, lkml, rust-for-linux
Subsystem:
chinese documentation, credentials, documentation, rust, the rest · Maintainers:
Alex Shi, Yanteng Si, Paul Moore, Jonathan Corbet, Miguel Ojeda, Linus Torvalds
task_euid() is a very weird operation. You can see how weird it is by grepping for task_euid() - binder is its only user. task_euid() obtains the objective effective UID - it looks at the credentials of the task for purposes of acting on it as an object, but then accesses the effective UID (which the credentials.7 man page describes as "[...] used by the kernel to determine the permissions that the process will have when accessing shared resources [...]"). Since usage in Binder has now been removed, get rid of the resulting dead code. Changes to the zh_CN translation was carried out with the help of Gemini and Google Translate, and since adjusted as per Alex Shi's feedback. Suggested-by: Jann Horn <jannh@google.com> Reviewed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Alice Ryhl <aliceryhl@google.com> --- Documentation/security/credentials.rst | 6 ++---- Documentation/translations/zh_CN/security/credentials.rst | 4 +--- include/linux/cred.h | 1 - rust/helpers/task.c | 5 ----- rust/kernel/task.rs | 10 ---------- 5 files changed, 3 insertions(+), 23 deletions(-)
diff --git a/Documentation/security/credentials.rst b/Documentation/security/credentials.rst
index 4996838491b1..a39a2a2f67aa 100644
--- a/Documentation/security/credentials.rst
+++ b/Documentation/security/credentials.rst@@ -393,16 +393,14 @@ the credentials so obtained when they're finished with. The result of ``__task_cred()`` should not be passed directly to ``get_cred()`` as this may race with ``commit_cred()``. -There are a couple of convenience functions to access bits of another task's -credentials, hiding the RCU magic from the caller:: +There is a convenience function to access bits of another task's credentials, +hiding the RCU magic from the caller:: uid_t task_uid(task) Task's real UID - uid_t task_euid(task) Task's effective UID If the caller is holding the RCU read lock at the time anyway, then:: __task_cred(task)->uid - __task_cred(task)->euid should be used instead. Similarly, if multiple aspects of a task's credentials need to be accessed, RCU read lock should be used, ``__task_cred()`` called,
diff --git a/Documentation/translations/zh_CN/security/credentials.rst b/Documentation/translations/zh_CN/security/credentials.rst
index 88fcd9152ffe..20c8696f8198 100644
--- a/Documentation/translations/zh_CN/security/credentials.rst
+++ b/Documentation/translations/zh_CN/security/credentials.rst@@ -337,15 +337,13 @@ const指针上操作，因此不需要进行类型转换，但需要临时放弃 ``__task_cred()`` 的结果不应直接传递给 ``get_cred()`` ， 因为这可能与 ``commit_cred()`` 发生竞争条件。 -还有一些方便的函数可以访问另一个任务凭据的特定部分，将RCU操作对调用方隐藏起来:: +有一个方便的函数可用于访问另一个任务凭据的特定部分，从而对调用方隐藏RCU机制:: uid_t task_uid(task) Task's real UID - uid_t task_euid(task) Task's effective UID 如果调用方在此时已经持有RCU读锁，则应使用:: __task_cred(task)->uid - __task_cred(task)->euid 类似地，如果需要访问任务凭据的多个方面，应使用RCU读锁，调用 ``__task_cred()`` 函数，将结果存储在临时指针中，然后从临时指针中调用凭据的各个方面，最后释放锁。
diff --git a/include/linux/cred.h b/include/linux/cred.h
index c6676265a985..6ef1750c93e2 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h@@ -371,7 +371,6 @@ DEFINE_FREE(put_cred, struct cred *, if (!IS_ERR_OR_NULL(_T)) put_cred(_T)) }) #define task_uid(task) (task_cred_xxx((task), uid)) -#define task_euid(task) (task_cred_xxx((task), euid)) #define task_ucounts(task) (task_cred_xxx((task), ucounts)) #define current_cred_xxx(xxx) \
diff --git a/rust/helpers/task.c b/rust/helpers/task.c
index c0e1a06ede78..b46b1433a67e 100644
--- a/rust/helpers/task.c
+++ b/rust/helpers/task.c@@ -28,11 +28,6 @@ __rust_helper kuid_t rust_helper_task_uid(struct task_struct *task) return task_uid(task); } -__rust_helper kuid_t rust_helper_task_euid(struct task_struct *task) -{ - return task_euid(task); -} - #ifndef CONFIG_USER_NS __rust_helper uid_t rust_helper_from_kuid(struct user_namespace *to, kuid_t uid) {
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index eabd65bfde12..c2b3457b700c 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs@@ -217,16 +217,6 @@ pub fn uid(&self) -> Kuid { Kuid::from_raw(unsafe { bindings::task_uid(self.as_ptr()) }) } - /// Returns the objective effective UID of the given task. - /// - /// You should probably not be using this; the effective UID is normally - /// only relevant in subjective credentials. - #[inline] - pub fn euid(&self) -> Kuid { - // SAFETY: It's always safe to call `task_euid` on a valid task. - Kuid::from_raw(unsafe { bindings::task_euid(self.as_ptr()) }) - } - /// Determines whether the given task has pending signals. #[inline] pub fn signal_pending(&self) -> bool {
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2.55.0.rc0.799.gd6f94ed593-goog