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Date:   Tue, 12 Oct 2021 09:56:11 -0700
Message-Id: <20211012165614.2873369-1-tkjos@google.com>
Mime-Version: 1.0
Subject: [PATCH v5 0/3] binder: use cred instead of task for security context
From:   Todd Kjos <tkjos@google.com>
To:     gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com,
        maco@android.com, christian@brauner.io, jmorris@namei.org,
        serge@hallyn.com, paul@paul-moore.com,
        stephen.smalley.work@gmail.com, eparis@parisplace.org,
        keescook@chromium.org, jannh@google.com, jeffv@google.com,
        zohar@linux.ibm.com, linux-security-module@vger.kernel.org,
        selinux@vger.kernel.org, devel@driverdev.osuosl.org,
        linux-kernel@vger.kernel.org
Cc:     joel@joelfernandes.org, kernel-team@android.com,
        Todd Kjos <tkjos@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

This series fixes the possible use of an incorrect security context
when checking selinux permissions, getting a security ID, or lookup
up the euid.

The previous behavior was to save the group_leader 'struct task_struct'
in binder_open() and using that to obtain security IDs or euids.

This has been shown to be unreliable, so this series instead saves the
'struct cred' of the task that called binder_open(). This cred is used
for these lookups instead of the task.

v1 and v2 of this series were a single patch "binder: use euid from"
cred instead of using task". During review, Stephen Smalley identified
two more related issues so the corresponding patches were added to
the series.

v3:
- add 2 patches to fix getsecid and euid

v4:
- fix minor checkpatch issues
- fix build-break for !CONFIG_SECURITY

v5:
- reorder/refactor patches as suggested by Stephen Smalley so eiud fix
  is first and saves the cred during binder_open()
- set *secid=0 for !CONFIG_SECURITY version of secuirty_cred_getsecid()

Todd Kjos (3):
  binder: use euid from cred instead of using task
  binder: use cred instead of task for selinux checks
  binder: use cred instead of task for getsecid

 drivers/android/binder.c          | 14 ++++++++------
 drivers/android/binder_internal.h |  4 ++++
 include/linux/lsm_hook_defs.h     | 14 +++++++-------
 include/linux/lsm_hooks.h         | 14 +++++++-------
 include/linux/security.h          | 28 ++++++++++++++--------------
 security/security.c               | 14 +++++++-------
 security/selinux/hooks.c          | 48 +++++++++++++-----------------------------------
 7 files changed, 60 insertions(+), 76 deletions(-)