[PATCH v5 1/3] binder: use euid from cred instead of using task
From: Todd Kjos <hidden>
Date: 2021-10-12 16:56:34
Also in:
lkml, selinux, stable
Subsystem:
android drivers, the rest · Maintainers:
Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos, Christian Brauner, Carlos Llamas, Alice Ryhl, Linus Torvalds
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.
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Signed-off-by: Todd Kjos <redacted>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Suggested-by: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org # 4.4+
---
v3: added this patch to series (as 3/3)
v5:
- combined with saving of 'struct cred' during binder_open()
- reordered to 1/1 as suggested by Stephen Smalley
drivers/android/binder.c | 4 +++-
drivers/android/binder_internal.h | 4 ++++
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 9edacc8b9768..a396015e874a 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c@@ -2711,7 +2711,7 @@ 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;
@@ -4353,6 +4353,7 @@ 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); }
@@ -5055,6 +5056,7 @@ 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); init_waitqueue_head(&proc->freeze_wait); proc->default_priority = task_nice(current);
diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
index 402c4d4362a8..d6b6b8cb7346 100644
--- a/drivers/android/binder_internal.h
+++ b/drivers/android/binder_internal.h@@ -364,6 +364,9 @@ struct binder_ref { * (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
@@ -426,6 +429,7 @@ 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; int outstanding_txns;
--
2.33.0.882.g93a45727a2-goog