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Commit 7dabb675 authored by Todd Kjos's avatar Todd Kjos Committed by Bernhard Thoben
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UPSTREAM: binder: use euid from cred instead of using task 



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.

Bug: 200688826
Cc: stable@vger.kernel.org # 4.4+
Fixes: 457b9a6f ("Staging: android: add binder driver")
Signed-off-by: default avatarTodd Kjos <tkjos@google.com>
Suggested-by: default avatarStephen Smalley <stephen.smalley.work@gmail.com>
Suggested-by: default avatarJann Horn <jannh@google.com>
Acked-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
Change-Id: I91922e7f359df5901749f1b09094c3c68d45aed4
(cherry picked from commit b3444eeb300e28d380ac8d716b7b6a3502acb3b4)
parent ebbaae99

drivers/android/binder.c

+7 −1
Original line number Diff line number Diff line
@@ -461,6 +461,9 @@ struct binder_priority { 
 * @files                 files_struct for process

 *                        (protected by @files_lock)

 * @files_lock            mutex to protect @files

 * @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
@@ -519,6 +522,7 @@ struct binder_proc { 
	struct task_struct *tsk;

	struct files_struct *files;

	struct mutex files_lock;

	const struct cred *cred;

	struct hlist_node deferred_work_node;

	int deferred_work;

	int outstanding_txns;
@@ -3181,7 +3185,7 @@ 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;
@@ -4634,6 +4638,7 @@ 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);

}
@@ -5342,6 +5347,7 @@ static int binder_open(struct inode *nodp, struct file *filp) 
	get_task_struct(current->group_leader);

	proc->tsk = current->group_leader;

	mutex_init(&proc->files_lock);

	proc->cred = get_cred(filp->f_cred);

	INIT_LIST_HEAD(&proc->todo);

	init_waitqueue_head(&proc->freeze_wait);

	if (binder_supported_policy(current->policy)) {