This is a note to let you know that I've just added the patch titled
binder: signal epoll threads of self-work
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
binder-signal-epoll-threads-of-self-work.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 97830f3c3088638ff90b20dfba2eb4d487bf14d7 Mon Sep 17 00:00:00 2001
From: Carlos Llamas <cmllamas@xxxxxxxxxx>
Date: Wed, 31 Jan 2024 21:53:46 +0000
Subject: binder: signal epoll threads of self-work
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From: Carlos Llamas <cmllamas@xxxxxxxxxx>
commit 97830f3c3088638ff90b20dfba2eb4d487bf14d7 upstream.
In (e)poll mode, threads often depend on I/O events to determine when
data is ready for consumption. Within binder, a thread may initiate a
command via BINDER_WRITE_READ without a read buffer and then make use
of epoll_wait() or similar to consume any responses afterwards.
It is then crucial that epoll threads are signaled via wakeup when they
queue their own work. Otherwise, they risk waiting indefinitely for an
event leaving their work unhandled. What is worse, subsequent commands
won't trigger a wakeup either as the thread has pending work.
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Cc: Arve Hjønnevåg <arve@xxxxxxxxxxx>
Cc: Martijn Coenen <maco@xxxxxxxxxxx>
Cc: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Cc: Steven Moreland <smoreland@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.19+
Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240131215347.1808751-1-cmllamas@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/android/binder.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -477,6 +477,16 @@ binder_enqueue_thread_work_ilocked(struc
{
WARN_ON(!list_empty(&thread->waiting_thread_node));
binder_enqueue_work_ilocked(work, &thread->todo);
+
+ /* (e)poll-based threads require an explicit wakeup signal when
+ * queuing their own work; they rely on these events to consume
+ * messages without I/O block. Without it, threads risk waiting
+ * indefinitely without handling the work.
+ */
+ if (thread->looper & BINDER_LOOPER_STATE_POLL &&
+ thread->pid == current->pid && !thread->process_todo)
+ wake_up_interruptible_sync(&thread->wait);
+
thread->process_todo = true;
}
Patches currently in stable-queue which might be from cmllamas@xxxxxxxxxx are
queue-6.1/binder-signal-epoll-threads-of-self-work.patch
