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

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Date:   Wed, 18 May 2022 09:17:54 +0800
From:   Schspa Shi <schspa@...il.com>
To:     gregkh@...uxfoundation.org, arve@...roid.com, tkjos@...roid.com,
        maco@...roid.com, joel@...lfernandes.org, brauner@...nel.org,
        hridya@...gle.com, surenb@...gle.com, cmllamas@...gle.com
Cc:     linux-kernel@...r.kernel.org, schspa@...il.com,
        syzbot+46fff6434a7f968ecb39@...kaller.appspotmail.com
Subject: [PATCH v2] binder: fix atomic sleep when get extended error

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@...kaller.appspotmail.com
Fixes: bd32889e841c ("binder: add BINDER_GET_EXTENDED_ERROR ioctl")
Signed-off-by: Schspa Shi <schspa@...il.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)