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AHgh+RoWusrZIyzqbO6wOTAX3xspVHHbl3uS791j284OtLNFeRKqUucnrT5fZJc0pPMwYywbBYRhOYz5EW9nZ0bd8pcjb+jFQ2I=@vger.kernel.org X-Gm-Message-State: AOJu0YyZdWF839dULkS5sHChUggXv5LSCXWuwMwh581RKo7qgg5SBHXS p6yxe0w5ux7dorOJOiC7pwIGPYsezd9+peKSlzGXRk744/y6ToBKn+VAJVFUqVDQQ0kW1TBv43/ OQjEQ7AzvSiaZzoehGw== X-Received: from wrxt5.prod.google.com ([2002:a05:6000:1c5:b0:46d:90df:9c14]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:2689:b0:472:55a:ef89 with SMTP id ffacd0b85a97d-47759097f62mr13285700f8f.27.1783061833360; Thu, 02 Jul 2026 23:57:13 -0700 (PDT) Date: Fri, 03 Jul 2026 06:57:02 +0000 In-Reply-To: <20260703-remove-task-euid-v5-0-c90c7e2ddf54@google.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260703-remove-task-euid-v5-0-c90c7e2ddf54@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=5389; i=aliceryhl@google.com; h=from:subject:message-id; bh=k7dZr0CQTzIcUvurCwCdMJZeoApiVYyv+YRvyaWrWfU=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBqR11Fem++4KKosCqI8D8y37ZxeOM4s61nbQk+I RxT/EXjjX+JAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCakddRQAKCRAEWL7uWMY5 RnmzEACZ/hgyrN3Ua95FLrJ8iWTcluJCg4Kt9ynUR7von/wbqiE7jVMzse6QA/HFqOnxepgKi7j poWLbwm7jnkoigmK5DoFGRlypwdN14RLjomQ7ih38G3QDvO94h7LsCemRZUNbjA+tW7AGnehaPm 8aEIwD7g8Rd3GDrf8tNaA59SCpKauREWe/QqFM1sdpzaIPyRtzVKzq/+LLkYCQ5NgIVa7ojVt4Y ZCCYZ+ZFodAakL1VE1krxN3qRWWMwyAGx9RZ225hueWYODKYN2inKyMzt++uoXGa24ggA1vhGa2 7435pI2XcTGKC+r6njgulMtZUdidFPO2s5/WS6d8cGfcWZxtVtF9oEbmaa6DXANGImUF47comj+ BqPrhVccUowl990JVPlgB6eY/wX4aYaz/QewUGueGhqPCHt4cOXZk4ARCmq3xGq2HCFXY+RTZRl MotQ6By/2f1vjd62hM47E8Cqr01WTDV4gVDR3EuJiFKJPzqWEW9VFLTNQIRkjh4KnFrXDZ8h4CG 3/nbTxt0NTDEyFTt743yTY4aJAvMa1EnA0TfnTOuoXv+om2vvoGlzyJPJtbREkXuDvZbgIyH8d5 0vzegkyHdyYsTg1QgcTLBA2PibJk0TgZ5l5Ih6NRoYxjSckojSvYgVBPiqAXR1XNJc5Rx5o+6Lo CLupUn4Rdj6fF7Q== X-Mailer: b4 0.14.3 Message-ID: <20260703-remove-task-euid-v5-2-c90c7e2ddf54@google.com> Subject: [PATCH v5 2/2] cred: delete task_euid() From: Alice Ryhl 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 , "=?utf-8?q?Bj=C3=B6rn_Roy_Baron?=" , Benno Lossin , Andreas Hindborg , Trevor Gross , Danilo Krummrich , Jann Horn , linux-security-module@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Alice Ryhl Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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 Reviewed-by: Gary Guo Signed-off-by: Alice Ryhl --- 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/securit= y/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 wit= h. The result of ``__task_cred()`` should not be passed directly to ``get_cred()`` as this may race with ``commit_cred()``. =20 -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 credentia= ls, +hiding the RCU magic from the caller:: =20 uid_t task_uid(task) Task's real UID - uid_t task_euid(task) Task's effective UID =20 If the caller is holding the RCU read lock at the time anyway, then:: =20 __task_cred(task)->uid - __task_cred(task)->euid =20 should be used instead. Similarly, if multiple aspects of a task's creden= tials need to be accessed, RCU read lock should be used, ``__task_cred()`` calle= d, diff --git a/Documentation/translations/zh_CN/security/credentials.rst b/Do= cumentation/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=E6=8C=87=E9=92=88=E4=B8=8A=E6=93=8D=E4=BD=9C=EF= =BC=8C=E5=9B=A0=E6=AD=A4=E4=B8=8D=E9=9C=80=E8=A6=81=E8=BF=9B=E8=A1=8C=E7=B1= =BB=E5=9E=8B=E8=BD=AC=E6=8D=A2=EF=BC=8C=E4=BD=86=E9=9C=80=E8=A6=81=E4=B8=B4= =E6=97=B6=E6=94=BE=E5=BC=83 ``__task_cred()`` =E7=9A=84=E7=BB=93=E6=9E=9C=E4=B8=8D=E5=BA=94=E7=9B= =B4=E6=8E=A5=E4=BC=A0=E9=80=92=E7=BB=99 ``get_cred()`` =EF=BC=8C =E5=9B=A0=E4=B8=BA=E8=BF=99=E5=8F=AF=E8=83=BD=E4=B8=8E ``commit_cred()`= ` =E5=8F=91=E7=94=9F=E7=AB=9E=E4=BA=89=E6=9D=A1=E4=BB=B6=E3=80=82 =20 -=E8=BF=98=E6=9C=89=E4=B8=80=E4=BA=9B=E6=96=B9=E4=BE=BF=E7=9A=84=E5=87=BD= =E6=95=B0=E5=8F=AF=E4=BB=A5=E8=AE=BF=E9=97=AE=E5=8F=A6=E4=B8=80=E4=B8=AA=E4= =BB=BB=E5=8A=A1=E5=87=AD=E6=8D=AE=E7=9A=84=E7=89=B9=E5=AE=9A=E9=83=A8=E5=88= =86=EF=BC=8C=E5=B0=86RCU=E6=93=8D=E4=BD=9C=E5=AF=B9=E8=B0=83=E7=94=A8=E6=96= =B9=E9=9A=90=E8=97=8F=E8=B5=B7=E6=9D=A5:: +=E6=9C=89=E4=B8=80=E4=B8=AA=E6=96=B9=E4=BE=BF=E7=9A=84=E5=87=BD=E6=95=B0= =E5=8F=AF=E7=94=A8=E4=BA=8E=E8=AE=BF=E9=97=AE=E5=8F=A6=E4=B8=80=E4=B8=AA=E4= =BB=BB=E5=8A=A1=E5=87=AD=E6=8D=AE=E7=9A=84=E7=89=B9=E5=AE=9A=E9=83=A8=E5=88= =86=EF=BC=8C=E4=BB=8E=E8=80=8C=E5=AF=B9=E8=B0=83=E7=94=A8=E6=96=B9=E9=9A=90= =E8=97=8FRCU=E6=9C=BA=E5=88=B6:: =20 uid_t task_uid(task) Task's real UID - uid_t task_euid(task) Task's effective UID =20 =E5=A6=82=E6=9E=9C=E8=B0=83=E7=94=A8=E6=96=B9=E5=9C=A8=E6=AD=A4=E6=97=B6= =E5=B7=B2=E7=BB=8F=E6=8C=81=E6=9C=89RCU=E8=AF=BB=E9=94=81=EF=BC=8C=E5=88=99= =E5=BA=94=E4=BD=BF=E7=94=A8:: =20 __task_cred(task)->uid - __task_cred(task)->euid =20 =E7=B1=BB=E4=BC=BC=E5=9C=B0=EF=BC=8C=E5=A6=82=E6=9E=9C=E9=9C=80=E8=A6=81= =E8=AE=BF=E9=97=AE=E4=BB=BB=E5=8A=A1=E5=87=AD=E6=8D=AE=E7=9A=84=E5=A4=9A=E4= =B8=AA=E6=96=B9=E9=9D=A2=EF=BC=8C=E5=BA=94=E4=BD=BF=E7=94=A8RCU=E8=AF=BB=E9= =94=81=EF=BC=8C=E8=B0=83=E7=94=A8 ``__task_cred()`` =E5=87=BD=E6=95=B0=EF=BC=8C=E5=B0=86=E7=BB=93=E6=9E=9C=E5=AD=98=E5=82=A8= =E5=9C=A8=E4=B8=B4=E6=97=B6=E6=8C=87=E9=92=88=E4=B8=AD=EF=BC=8C=E7=84=B6=E5= =90=8E=E4=BB=8E=E4=B8=B4=E6=97=B6=E6=8C=87=E9=92=88=E4=B8=AD=E8=B0=83=E7=94= =A8=E5=87=AD=E6=8D=AE=E7=9A=84=E5=90=84=E4=B8=AA=E6=96=B9=E9=9D=A2=EF=BC=8C= =E6=9C=80=E5=90=8E=E9=87=8A=E6=94=BE=E9=94=81=E3=80=82 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_NUL= L(_T)) put_cred(_T)) }) =20 #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)) =20 #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_st= ruct *task) return task_uid(task); } =20 -__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()) }) } =20 - /// Returns the objective effective UID of the given task. - /// - /// You should probably not be using this; the effective UID is normal= ly - /// 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 { --=20 2.55.0.rc0.799.gd6f94ed593-goog