From ddf30b829a804a3c30e3fa04078c5eefad077b10 Mon Sep 17 00:00:00 2001 From: Todd Kjos Date: Tue, 9 May 2017 08:31:32 -0700 Subject: [PATCH] FROMLIST: binder: avoid race conditions when enqueuing txn (from https://patchwork.kernel.org/patch/9817813/) Currently, the transaction complete work item is queued after the transaction. This means that it is possible for the transaction to be handled and a reply to be enqueued in the current thread before the transaction complete is enqueued, which violates the protocol with userspace who may not expect the transaction complete. Fixed by always enqueing the transaction complete first. Also, once the transaction is enqueued, it is unsafe to access since it might be freed. Currently, t->flags is accessed to determine whether a sync wake is needed. Changed to access tr->flags instead. Change-Id: I6c01566e167a39cf17c9027c3817618182e56975 Signed-off-by: Todd Kjos --- drivers/android/binder.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index d11de47f1d78..0c7f5972ccfb 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -1801,6 +1801,9 @@ static void binder_transaction(struct binder_proc *proc, goto err_bad_object_type; } } + tcomplete->type = BINDER_WORK_TRANSACTION_COMPLETE; + list_add_tail(&tcomplete->entry, &thread->todo); + if (reply) { BUG_ON(t->buffer->async_transaction != 0); binder_pop_transaction(target_thread, in_reply_to); @@ -1820,10 +1823,8 @@ static void binder_transaction(struct binder_proc *proc, } t->work.type = BINDER_WORK_TRANSACTION; list_add_tail(&t->work.entry, target_list); - tcomplete->type = BINDER_WORK_TRANSACTION_COMPLETE; - list_add_tail(&tcomplete->entry, &thread->todo); if (target_wait) { - if (reply || !(t->flags & TF_ONE_WAY)) + if (reply || !(tr->flags & TF_ONE_WAY)) wake_up_interruptible_sync(target_wait); else wake_up_interruptible(target_wait);