4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Carlos Llamas <cmllamas@xxxxxxxxxx>
commit 31643d84b8c3d9c846aa0e20bc033e46c68c7e7d upstream.
With the introduction of binder_available_for_proc_work_ilocked() in
commit 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue") a binder
thread can only "wait_for_proc_work" after its thread->looper has been
marked as BINDER_LOOPER_STATE_{ENTERED|REGISTERED}.
This means an unregistered reader risks waiting indefinitely for work
since it never gets added to the proc->waiting_threads. If there are no
further references to its waitqueue either the task will hang. The same
applies to readers using the (e)poll interface.
I couldn't find the rationale behind this restriction. So this patch
restores the previous behavior of allowing unregistered threads to
"wait_for_proc_work". Note that an error message for this scenario,
which had previously become unreachable, is now re-enabled.
Fixes: 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue")
Cc: stable@xxxxxxxxxxxxxxx
Cc: Martijn Coenen <maco@xxxxxxxxxx>
Cc: Arve Hjønnevåg <arve@xxxxxxxxxx>
Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240711201452.2017543-1-cmllamas@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/android/binder.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -998,9 +998,7 @@ static bool binder_has_work(struct binde
static bool binder_available_for_proc_work_ilocked(struct binder_thread *thread)
{
return !thread->transaction_stack &&
- binder_worklist_empty_ilocked(&thread->todo) &&
- (thread->looper & (BINDER_LOOPER_STATE_ENTERED |
- BINDER_LOOPER_STATE_REGISTERED));
+ binder_worklist_empty_ilocked(&thread->todo);
}
static void binder_wakeup_poll_threads_ilocked(struct binder_proc *proc,
