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binder: avoid race conditions when enqueuing txn

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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.

Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Todd Kjos 2017-06-29 12:01:48 -07:00 committed by Greg Kroah-Hartman
parent 26b47d8a16
commit ccae6f6760
1 changed files with 4 additions and 3 deletions
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7
drivers/android/binder.c
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@ -1799,6 +1799,9 @@ 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);
@ -1818,10 +1821,8 @@ 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);