[v4,0/3] binder: use cred instead of task for security context

Message

Todd Kjos Oct. 7, 2021, 12:46 a.m. UTC

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

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

 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(-)