linux-kernel - [PATCH 1/4] binder: introduce BINDER_SET_PROC

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Date: Wed, 17 Apr 2024 19:13:41 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Arve Hjønnevåg" <arve@...roid.com>, Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>, 
	Joel Fernandes <joel@...lfernandes.org>, Christian Brauner <brauner@...nel.org>, 
	Carlos Llamas <cmllamas@...gle.com>, Suren Baghdasaryan <surenb@...gle.com>, 
	Alice Ryhl <aliceryhl@...gle.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: [PATCH 1/4] binder: introduce BINDER_SET_PROC_FLAGS ioctl

This new ioctl enables userspace to control the individual behavior of
the 'struct binder_proc' instance via flags. The driver validates and
returns the supported subset. Some existing ioctls are migrated to use
these flags in subsequent commits.

Suggested-by: Arve Hjønnevåg <arve@...roid.com>
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
 drivers/android/binder.c            | 25 +++++++++++++++++++++++++
 drivers/android/binder_internal.h   |  4 +++-
 include/uapi/linux/android/binder.h |  6 ++++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index bad28cf42010..e0d193bfb237 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5334,6 +5334,26 @@ static int binder_ioctl_get_extended_error(struct binder_thread *thread,
 	return 0;
 }
 
+static int binder_ioctl_set_proc_flags(struct binder_proc *proc,
+				       u32 __user *user)
+{
+	u32 flags;
+
+	if (get_user(flags, user))
+		return -EFAULT;
+
+	binder_inner_proc_lock(proc);
+	flags &= PF_SUPPORTED_FLAGS_MASK;
+	proc->flags = flags;
+	binder_inner_proc_unlock(proc);
+
+	/* confirm supported flags with user */
+	if (put_user(flags, user))
+		return -EFAULT;
+
+	return 0;
+}
+
 static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	int ret;
@@ -5542,6 +5562,11 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (ret < 0)
 			goto err;
 		break;
+	case BINDER_SET_PROC_FLAGS:
+		ret = binder_ioctl_set_proc_flags(proc, ubuf);
+		if (ret < 0)
+			goto err;
+		break;
 	default:
 		ret = -EINVAL;
 		goto err;
diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
index 7270d4d22207..a22e64cddbae 100644
--- a/drivers/android/binder_internal.h
+++ b/drivers/android/binder_internal.h
@@ -346,6 +346,8 @@ struct binder_ref {
  * @cred                  struct cred associated with the `struct file`
  *                        in binder_open()
  *                        (invariant after initialized)
+ * @flags:                enum proc_flags set via BINDER_SET_PROC_FLAGS.
+ *                        (protected by @inner_lock)
  * @deferred_work_node:   element for binder_deferred_list
  *                        (protected by binder_deferred_lock)
  * @deferred_work:        bitmap of deferred work to perform
@@ -409,6 +411,7 @@ struct binder_proc {
 	int pid;
 	struct task_struct *tsk;
 	const struct cred *cred;
+	u32 flags;
 	struct hlist_node deferred_work_node;
 	int deferred_work;
 	int outstanding_txns;
@@ -417,7 +420,6 @@ struct binder_proc {
 	bool sync_recv;
 	bool async_recv;
 	wait_queue_head_t freeze_wait;
-
 	struct list_head todo;
 	struct binder_stats stats;
 	struct list_head delivered_death;
diff --git a/include/uapi/linux/android/binder.h b/include/uapi/linux/android/binder.h
index d44a8118b2ed..281a8e2e734e 100644
--- a/include/uapi/linux/android/binder.h
+++ b/include/uapi/linux/android/binder.h
@@ -251,6 +251,11 @@ struct binder_extended_error {
 	__s32	param;
 };
 
+/* Used with BINDER_SET_PROC_FLAGS ioctl */
+enum proc_flags {
+	PF_SUPPORTED_FLAGS_MASK,
+};
+
 enum {
 	BINDER_WRITE_READ		= _IOWR('b', 1, struct binder_write_read),
 	BINDER_SET_IDLE_TIMEOUT		= _IOW('b', 3, __s64),
@@ -266,6 +271,7 @@ enum {
 	BINDER_GET_FROZEN_INFO		= _IOWR('b', 15, struct binder_frozen_status_info),
 	BINDER_ENABLE_ONEWAY_SPAM_DETECTION	= _IOW('b', 16, __u32),
 	BINDER_GET_EXTENDED_ERROR	= _IOWR('b', 17, struct binder_extended_error),
+	BINDER_SET_PROC_FLAGS		= _IOWR('b', 18, __u32),
 };
 
 /*
-- 
2.44.0.683.g7961c838ac-goog