hurd: Replace reply port with a dead name on failed interruption

If we're trying to interrupt an interruptible RPC, but the server fails
to respond to our __interrupt_operation () call, we instead destroy the
reply port we were expecting the reply to the RPC on.

Instead of deallocating the name completely, replace it with a dead
name, so the name won't get reused for some other right, and deallocate
it in _hurd_intr_rpc_mach_msg once we return from the signal handler.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230429201822.2605207-4-bugaevc@gmail.com>

2 files changed, 13 insertions, 3 deletions

diff --git a/hurd/hurdsig.c b/hurd/hurdsig.c
index b3808f9e49..78ea59d97d 100644
--- a/hurd/hurdsig.c
+++ b/hurd/hurdsig.c
@@ -477,9 +477,18 @@ _hurdsig_abort_rpcs (struct hurd_sigstate *ss, int signo, int sigthread,
           if (reply)
             {
               /* The interrupt didn't work.
-                 Destroy the receive right the thread is blocked on.  */
-              __mach_port_destroy (__mach_task_self (), *reply);
-              *reply = MACH_PORT_NULL;
+                 Destroy the receive right the thread is blocked on, and
+                 replace it with a dead name to keep the name from reuse until
+                 the therad is done with it.  To do this atomically, first
+                 insert a send right, and then destroy the receive right,
+                 turning the send right into a dead name.  */
+              err = __mach_port_insert_right (__mach_task_self (),
+                                              *reply, *reply,
+                                              MACH_MSG_TYPE_MAKE_SEND);
+              assert_perror (err);
+              err = __mach_port_mod_refs (__mach_task_self (), *reply,
+                                          MACH_PORT_RIGHT_RECEIVE, -1);
+              assert_perror (err);
             }
 
           /* The system call return value register now contains
diff --git a/hurd/intr-msg.c b/hurd/intr-msg.c
index 1a086b5141..716d87ab6a 100644
--- a/hurd/intr-msg.c
+++ b/hurd/intr-msg.c
@@ -305,6 +305,7 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
 	{
 	  /* Make sure we have a valid reply port.  The one we were using
 	     may have been destroyed by interruption.  */
+	  __mig_dealloc_reply_port (rcv_name);
 	  m->header.msgh_local_port = rcv_name = __mig_get_reply_port ();
 	  m->header.msgh_bits = msgh_bits;
 	  option = user_option;