From 22676a3a6e4d99e13ee75c1ad2f4976ae6b0ce52 Mon Sep 17 00:00:00 2001
From: Damien Zammit <damien@zamaudio.com>
Date: Thu, 8 Sep 2022 09:32:52 +0000
Subject: machdev, pci-arbiter, rumpdisk: Fix race condition in bootstrap

This fixes a known race condition in bootstrapping by
separating the fsys_startup call from the server demuxer loop
into two separate functions that the caller can decide
when to call.
Message-Id: <20220908093229.499494-1-damien@zamaudio.com>
---
 libmachdev/machdev.h       |  3 ++-
 libmachdev/trivfs_server.c | 18 ++++++++++++------
 2 files changed, 14 insertions(+), 7 deletions(-)

(limited to 'libmachdev')

diff --git a/libmachdev/machdev.h b/libmachdev/machdev.h
index e1833cff..50bfd41b 100644
--- a/libmachdev/machdev.h
+++ b/libmachdev/machdev.h
@@ -37,7 +37,8 @@ void * machdev_server(void *);
 error_t machdev_create_device_port (size_t size, void *result);
 int machdev_trivfs_init(int argc, char **argv, mach_port_t bootstrap_resume_task, const char *name, const char *path, mach_port_t *bootstrap);
 int machdev_demuxer(mach_msg_header_t *inp, mach_msg_header_t *outp);
-void machdev_trivfs_server(mach_port_t bootstrap);
+void machdev_trivfs_server_startup(mach_port_t bootstrap);
+void * machdev_trivfs_server_loop(void *);
 boolean_t machdev_is_master_device (mach_port_t port);
 
 #endif
diff --git a/libmachdev/trivfs_server.c b/libmachdev/trivfs_server.c
index 21684dab..979741d1 100644
--- a/libmachdev/trivfs_server.c
+++ b/libmachdev/trivfs_server.c
@@ -84,6 +84,9 @@ static task_t parent_task;
 /* Our argument vector */
 static char **machdev_argv;
 
+/* Our trivfs control port to use in server loop */
+static struct trivfs_control *global_fsys;
+
 static void
 install_as_translator (mach_port_t bootport)
 {
@@ -513,9 +516,8 @@ trivfs_modify_stat (struct trivfs_protid *cred, io_statbuf_t *stat)
 }
 
 void
-machdev_trivfs_server(mach_port_t bootstrap)
+machdev_trivfs_server_startup(mach_port_t bootstrap)
 {
-  struct trivfs_control *fsys = NULL;
   int err;
 
   if (bootstrapping == FALSE)
@@ -523,7 +525,7 @@ machdev_trivfs_server(mach_port_t bootstrap)
       /* This path is executed when a parent exists */
       err = trivfs_startup (bootstrap, 0,
                             trivfs_cntl_class, port_bucket,
-                            trivfs_protid_class, port_bucket, &fsys);
+                            trivfs_protid_class, port_bucket, &global_fsys);
       mach_port_deallocate (mach_task_self (), bootstrap);
       if (err)
         error (1, err, "Contacting parent");
@@ -532,14 +534,18 @@ machdev_trivfs_server(mach_port_t bootstrap)
     }
   else
     {
-      fsys = control;
+      global_fsys = control;
     }
+}
 
+void *
+machdev_trivfs_server_loop(void *arg)
+{
   /* Launch.  */
   do
     {
       ports_manage_port_operations_one_thread (port_bucket, demuxer, 0);
-    } while (trivfs_goaway (fsys, 0));
+    } while (trivfs_goaway (global_fsys, 0));
 
-  /* Never reached */
+  return NULL;
 }
-- 
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