This is a note to let you know that I've just added the patch titled
binder: use euid from cred instead of using task
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
binder-use-euid-from-cred-instead-of-using-task.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <sta...@vger.kernel.org> know about it.
>From foo@baz Sat Nov 13 12:23:35 PM CET 2021
From: Todd Kjos <tk...@google.com>
Date: Wed, 10 Nov 2021 15:00:34 -0800
Subject: binder: use euid from cred instead of using task
To: sta...@vger.kernel.org, gre...@linuxfoundation.org, a...@android.com,
tk...@android.com, m...@android.com, christ...@brauner.io, jmor...@namei.org,
se...@hallyn.com, p...@paul-moore.com, stephen.smalley.w...@gmail.com,
epa...@parisplace.org, keesc...@chromium.org, ja...@google.com,
je...@google.com, zo...@linux.ibm.com, linux-security-mod...@vger.kernel.org,
seli...@vger.kernel.org, de...@driverdev.osuosl.org
Cc: j...@joelfernandes.org, kernel-t...@android.com, Todd Kjos
<tk...@google.com>, Casey Schaufler <ca...@schaufler-ca.com>
Message-ID: <20211110230036.3274365-1-tk...@google.com>
From: Todd Kjos <tk...@google.com>
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: sta...@vger.kernel.org # 4.4+
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Signed-off-by: Todd Kjos <tk...@google.com>
Suggested-by: Stephen Smalley <stephen.smalley.w...@gmail.com>
Suggested-by: Jann Horn <ja...@google.com>
Acked-by: Casey Schaufler <ca...@schaufler-ca.com>
Signed-off-by: Paul Moore <p...@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/android/binder.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- 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;
@@ -3087,7 +3091,7 @@ static void binder_transaction(struct bi
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 bind
}
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 *nod
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 */
Patches currently in stable-queue which might be from tk...@google.com are
queue-5.10/binder-use-cred-instead-of-task-for-selinux-checks.patch
queue-5.10/binder-use-cred-instead-of-task-for-getsecid.patch
queue-5.10/binder-use-euid-from-cred-instead-of-using-task.patch
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