From: Todd Kjos <tkjos@google.com>
To: stable@vger.kernel.org, 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
Cc: joel@joelfernandes.org, kernel-team@android.com,
Todd Kjos <tkjos@google.com>,
Casey Schaufler <casey@schaufler-ca.com>
Subject: [PATCH 5.10 1/3] binder: use euid from cred instead of using task
Date: Wed, 10 Nov 2021 15:00:34 -0800 [thread overview]
Message-ID: <20211110230036.3274365-1-tkjos@google.com> (raw)
commit 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b upstream.
Save the 'struct cred' associated with a binder process
at initial open to avoid potential race conditions
when converting to an euid.
Set a transaction's sender_euid from the 'struct cred'
saved at binder_open() instead of looking up the euid
from the binder proc's 'struct task'. This ensures
the euid is associated with the security context that
of the task that opened binder.
Cc: stable@vger.kernel.org # 4.4+
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Signed-off-by: Todd Kjos <tkjos@google.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Suggested-by: Jann Horn <jannh@google.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Change-Id: I91922e7f359df5901749f1b09094c3c68d45aed4
---
drivers/android/binder.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 65b22b5af51a..4e33f6e42ac4 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -420,6 +420,9 @@ enum binder_deferred_state {
* (invariant after initialized)
* @tsk task_struct for group_leader of process
* (invariant after initialized)
+ * @cred struct cred associated with the `struct file`
+ * in binder_open()
+ * (invariant after initialized)
* @deferred_work_node: element for binder_deferred_list
* (protected by binder_deferred_lock)
* @deferred_work: bitmap of deferred work to perform
@@ -465,6 +468,7 @@ struct binder_proc {
struct list_head waiting_threads;
int pid;
struct task_struct *tsk;
+ const struct cred *cred;
struct hlist_node deferred_work_node;
int deferred_work;
bool is_dead;
@@ -3088,7 +3092,7 @@ static void binder_transaction(struct binder_proc *proc,
t->from = thread;
else
t->from = NULL;
- t->sender_euid = task_euid(proc->tsk);
+ t->sender_euid = proc->cred->euid;
t->to_proc = target_proc;
t->to_thread = target_thread;
t->code = tr->code;
@@ -4703,6 +4707,7 @@ static void binder_free_proc(struct binder_proc *proc)
}
binder_alloc_deferred_release(&proc->alloc);
put_task_struct(proc->tsk);
+ put_cred(proc->cred);
binder_stats_deleted(BINDER_STAT_PROC);
kfree(proc);
}
@@ -5220,6 +5225,7 @@ static int binder_open(struct inode *nodp, struct file *filp)
spin_lock_init(&proc->outer_lock);
get_task_struct(current->group_leader);
proc->tsk = current->group_leader;
+ proc->cred = get_cred(filp->f_cred);
INIT_LIST_HEAD(&proc->todo);
proc->default_priority = task_nice(current);
/* binderfs stashes devices in i_private */
--
2.34.0.rc0.344.g81b53c2807-goog
next reply other threads:[~2021-11-10 23:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-10 23:00 Todd Kjos [this message]
2021-11-10 23:00 ` [PATCH 5.10 2/3] binder: use cred instead of task for selinux checks Todd Kjos
2021-11-10 23:00 ` [PATCH 5.10 3/3] binder: use cred instead of task for getsecid Todd Kjos
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