linux-kernel - [PATCH 1/2] rust_binder: freeze_notif

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Message-ID: <20251004-binder-freeze-v1-1-fb9fcdcf2b73@google.com>
Date: Sat, 04 Oct 2025 10:07:57 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Arve Hjønnevåg" <arve@...roid.com>, Todd Kjos <tkjos@...roid.com>, 
	Martijn Coenen <maco@...roid.com>, Joel Fernandes <joelagnelf@...dia.com>, 
	Christian Brauner <brauner@...nel.org>, Carlos Llamas <cmllamas@...gle.com>, 
	Suren Baghdasaryan <surenb@...gle.com>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH 1/2] rust_binder: freeze_notif_done should resend if wrong state

Consider the following scenario:
1. A freeze notification is delivered to thread 1.
2. The process becomes frozen or unfrozen.
3. The message for step 2 is delivered to thread 2 and ignored because
   there is already a pending notification from step 1.
4. Thread 1 acknowledges the notification from step 1.
In this case, step 4 should ensure that the message ignored in step 3 is
resent as it can now be delivered.

Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 drivers/android/binder/freeze.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/android/binder/freeze.rs b/drivers/android/binder/freeze.rs
index e68c3c8bc55a203c32261c23915d8c427569e3b0..74bebb8d4d9b24860eed34363ce69b1c6df58028 100644
--- a/drivers/android/binder/freeze.rs
+++ b/drivers/android/binder/freeze.rs
@@ -245,8 +245,9 @@ pub(crate) fn freeze_notif_done(self: &Arc<Self>, reader: &mut UserSliceReader)
                 );
                 return Err(EINVAL);
             }
-            if freeze.is_clearing {
-                // Immediately send another FreezeMessage for BR_CLEAR_FREEZE_NOTIFICATION_DONE.
+            let is_frozen = freeze.node.owner.inner.lock().is_frozen;
+            if freeze.is_clearing || freeze.last_is_frozen != Some(is_frozen) {
+                // Immediately send another FreezeMessage.
                 clear_msg = Some(FreezeMessage::init(alloc, cookie));
             }
             freeze.is_pending = false;

-- 
2.51.0.618.g983fd99d29-goog