commit 7fa495cdf750c257ed897eca189aabc3a62d5f2b
Author: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date:   Sat Nov 10 11:20:12 2018 +0000

    Hurd: Fix ulinks in fd table reallocation
    
            * hurd/hurd/userlink.h (_hurd_userlink_move): New function.
            * hurd/hurd/port.h (_hurd_port_move): New function.
            * sysdeps/mach/hurd/spawni.c (NEW_ULINK_TABLE): New macro.
            (EXPAND_DTABLE): Use NEW_ULINK_TABLE macro for ulink_dtable.

commit 278fdabd8c45dc215222facd36febfc3f6f2a95d
Author: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date:   Sun Nov 11 20:08:29 2018 +0100

    hurd: Fix spawni's user_link reallocation
    
    * hurd/hurd/userlink.h (_hurd_userlink_move): Make new_link's
    predecessor point to new_link instead of link.

---
 hurd/hurd/port.h           |   25 +++++++++++++++++++++++++
 hurd/hurd/userlink.h       |   24 ++++++++++++++++++++++++
 sysdeps/mach/hurd/spawni.c |   12 +++++++++++-
 3 files changed, 60 insertions(+), 1 deletion(-)

--- a/hurd/hurd/port.h
+++ b/hurd/hurd/port.h
@@ -128,6 +128,31 @@ _hurd_port_get (struct hurd_port *port,
 #endif
 
 
+/* Relocate LINK to NEW_LINK.
+   To be used when e.g. reallocating a link array.  */
+
+extern void
+_hurd_port_move (struct hurd_port *port,
+		 struct hurd_userlink *new_link,
+		 struct hurd_userlink *link);
+
+#if defined __USE_EXTERN_INLINES && defined _LIBC
+# if IS_IN (libc)
+_HURD_PORT_H_EXTERN_INLINE void
+_hurd_port_move (struct hurd_port *port,
+		 struct hurd_userlink *new_link,
+		 struct hurd_userlink *link)
+{
+  HURD_CRITICAL_BEGIN;
+  __spin_lock (&port->lock);
+  _hurd_userlink_move (new_link, link);
+  __spin_unlock (&port->lock);
+  HURD_CRITICAL_END;
+}
+# endif
+#endif
+
+
 /* Free a reference gotten with `USED_PORT = _hurd_port_get (PORT, LINK);' */
 
 extern void
--- a/hurd/hurd/userlink.h
+++ b/hurd/hurd/userlink.h
@@ -138,6 +138,30 @@ _hurd_userlink_unlink (struct hurd_userl
 # endif
 #endif
 
+/* Relocate LINK to NEW_LINK.
+   To be used when e.g. reallocating a link array.  */
+
+extern void _hurd_userlink_move (struct hurd_userlink *new_link,
+                                struct hurd_userlink *link);
+
+#if defined __USE_EXTERN_INLINES && defined _LIBC
+# if IS_IN (libc)
+_HURD_USERLINK_H_EXTERN_INLINE void
+_hurd_userlink_move (struct hurd_userlink *new_link,
+                     struct hurd_userlink *link)
+{
+  *new_link = *link;
+
+  if (new_link->resource.next != NULL)
+    new_link->resource.next->resource.prevp = &new_link->resource.next;
+  *new_link->resource.prevp = new_link;
+
+  if (new_link->thread.next != NULL)
+    new_link->thread.next->thread.prevp = &new_link->thread.next;
+  *new_link->thread.prevp = new_link;
+}
+# endif
+#endif
 
 /* Clear all users from *CHAINP.  Call this when the resource *CHAINP
    protects is changing.  If the return value is nonzero, no users are on
--- a/sysdeps/mach/hurd/spawni.c
+++ b/sysdeps/mach/hurd/spawni.c
@@ -406,7 +406,7 @@ __spawni (pid_t *pid, const char *file,
 	    {								      \
 	      /* We need to expand the dtable for the child.  */	      \
 	      NEW_TABLE (dtable, newfd);				      \
-	      NEW_TABLE (ulink_dtable, newfd);				      \
+	      NEW_ULINK_TABLE (ulink_dtable, newfd);			      \
 	      NEW_TABLE (dtable_cells, newfd);				      \
 	      dtablesize = newfd + 1;					      \
 	    }								      \
@@ -417,6 +417,16 @@ __spawni (pid_t *pid, const char *file,
   memcpy (new_##x, x, dtablesize * sizeof (x[0]));			      \
   memset (&new_##x[dtablesize], 0, (newfd + 1 - dtablesize) * sizeof (x[0])); \
   x = new_##x; } while (0)
+#define NEW_ULINK_TABLE(x, newfd) \
+  do { __typeof (x) new_##x = __alloca ((newfd + 1) * sizeof (x[0]));	      \
+  unsigned i;								      \
+  for (i = 0; i < dtablesize; i++)					      \
+    if (dtable_cells[i] != NULL)					      \
+      _hurd_port_move (dtable_cells[i], &new_##x[i], &x[i]);		      \
+    else								      \
+      memset(&new_##x[i], 0, sizeof(new_##x[i]));			      \
+  memset (&new_##x[dtablesize], 0, (newfd + 1 - dtablesize) * sizeof (x[0])); \
+  x = new_##x; } while (0)
 
 	struct __spawn_action *action = &file_actions->__actions[i];