binder: prevent transactions to context manager from its own process.

commit 49ed96943a8e0c62cc5a9b0a6cfc88be87d1fcec upstream.

Currently, a transaction to context manager from its own process
is prevented by checking if its binder_proc struct is the same as
that of the sender. However, this would not catch cases where the
process opens the binder device again and uses the new fd to send
a transaction to the context manager.

Reported-by: syzbot+8b3c354d33c4ac78bfad@syzkaller.appspotmail.com
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Acked-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20190715191804.112933-1-hridya@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 1af9f36f89cfb41de6bd60ab54031d44cd6aeb62..e694fd2c4ed0fd08d744bed8a72a4b13512f3e58 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2785,7 +2785,7 @@ static void binder_transaction(struct binder_proc *proc,
                        else
                                return_error = BR_DEAD_REPLY;
                        mutex_unlock(&context->context_mgr_node_lock);
-                       if (target_node && target_proc == proc) {
+                       if (target_node && target_proc->pid == proc->pid) {
                                binder_user_error("%d:%d got transaction to context manager from process owning it\n",
                                                  proc->pid, thread->pid);
                                return_error = BR_FAILED_REPLY;