linux-kernel - [PATCH v5 0/3] binder: use cred instead of task for security context

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Message-Id: <20211012165614.2873369-1-tkjos@google.com>
Date:   Tue, 12 Oct 2021 09:56:11 -0700
From:   Todd Kjos <tkjos@...gle.com>
To:     gregkh@...uxfoundation.org, arve@...roid.com, tkjos@...roid.com,
        maco@...roid.com, christian@...uner.io, jmorris@...ei.org,
        serge@...lyn.com, paul@...l-moore.com,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        keescook@...omium.org, jannh@...gle.com, jeffv@...gle.com,
        zohar@...ux.ibm.com, linux-security-module@...r.kernel.org,
        selinux@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Cc:     joel@...lfernandes.org, kernel-team@...roid.com,
        Todd Kjos <tkjos@...gle.com>
Subject: [PATCH v5 0/3] binder: use cred instead of task for security context

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(-)