[PATCH v2] binder: fix atomic sleep when get extended error

From: Schspa Shi <schspa@gmail.com>
To: gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com,
	maco@android.com, joel@joelfernandes.org, brauner@kernel.org,
	hridya@google.com, surenb@google.com, cmllamas@google.com
Cc: linux-kernel@vger.kernel.org, schspa@gmail.com,
	syzbot+46fff6434a7f968ecb39@syzkaller.appspotmail.com
Subject: [PATCH v2] binder: fix atomic sleep when get extended error
Date: Wed, 18 May 2022 09:17:54 +0800	[thread overview]
Message-ID: <20220518011754.49348-1-schspa@gmail.com> (raw)

binder_inner_proc_lock(thread->proc) is a spin lock, copy_to_user can't
be called with in this lock.

Copy it as a local variable to fix it.

Reported-by: syzbot+46fff6434a7f968ecb39@syzkaller.appspotmail.com
Fixes: bd32889e841c ("binder: add BINDER_GET_EXTENDED_ERROR ioctl")
Signed-off-by: Schspa Shi <schspa@gmail.com>

---

Changelog:
v1 -> v2:
        - Remove the retry as Carlos Llamas adviced.
        - Use binder_set_extended_error to reset the error info.
---
 drivers/android/binder.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index d9253b2a7bd9..1a6b7a8c8346 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5162,19 +5162,16 @@ static int binder_ioctl_get_freezer_info(
 static int binder_ioctl_get_extended_error(struct binder_thread *thread,
 					   void __user *ubuf)
 {
-	struct binder_extended_error *ee = &thread->ee;
+	struct binder_extended_error ee;
 
 	binder_inner_proc_lock(thread->proc);
-	if (copy_to_user(ubuf, ee, sizeof(*ee))) {
-		binder_inner_proc_unlock(thread->proc);
-		return -EFAULT;
-	}
-
-	ee->id = 0;
-	ee->command = BR_OK;
-	ee->param = 0;
+	ee = thread->ee;
+	binder_set_extended_error(&thread->ee, 0, BR_OK, 0);
 	binder_inner_proc_unlock(thread->proc);
 
+	if (copy_to_user(ubuf, &ee, sizeof(ee)))
+		return -EFAULT;
+
 	return 0;
 }
 
-- 
2.24.3 (Apple Git-128)

