selinux: fix data race on AVC latest_notif

avc_policy_seqno() reads latest_notif without holding notif_lock, while
avc_latest_notif_update() can update it under that lock. KCSAN reports
these concurrent accesses during policy boolean updates and permission
checks.

Use READ_ONCE() for the lockless read and WRITE_ONCE() for the update.
The spinlock continues to serialize the comparison and update against
other writers. Reads made while holding notif_lock cannot race with a
writer and can remain plain accesses.

This marks both sides of the intentional concurrent access and constrains
compiler transformations, without suppressing checking with data_race().

Cc: stable@vger.kernel.org
Fixes: 788e7dd4c22e ("SELinux: Improve read/write performance")
Reported-by: syzbot+a7f7cb0737bd91aa698c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=a7f7cb0737bd91aa698c
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

0 files changed, 0 insertions, 0 deletions