[PATCH 09/13] trans: fix locking in fakeroot's netfs_S_dir_lookup

[Justus Winter]

* trans/fakeroot.c (netfs_S_dir_lookup): Fix locking.
---
 trans/fakeroot.c |   45 ++++++++++++++++++++++++++++-----------------
 1 file changed, 28 insertions(+), 17 deletions(-)

diff --git a/trans/fakeroot.c b/trans/fakeroot.c
index eff5225..d5cb0e6 100644
--- a/trans/fakeroot.c
+++ b/trans/fakeroot.c
@@ -322,7 +322,10 @@ netfs_S_dir_lookup (struct protid *diruser,
   np = 0;
   err = io_identity (file, &idport, &fsidport, &fileno);
   if (err)
-    mach_port_deallocate (mach_task_self (), file);
+    {
+      mach_port_deallocate (mach_task_self (), file);
+      return err;
+    }
   else
     {
       mach_port_deallocate (mach_task_self (), fsidport);
@@ -335,6 +338,7 @@ netfs_S_dir_lookup (struct protid *diruser,
       else
        {
          pthread_mutex_lock (&idport_ihash_lock);
+         pthread_mutex_lock (&dnp->lock);
          struct netnode *nn = hurd_ihash_find (&idport_ihash, idport);
          if (nn != NULL)
            {
@@ -342,33 +346,38 @@ netfs_S_dir_lookup (struct protid *diruser,
              np = nn->np;
              /* We already know about this node.  */
              mach_port_deallocate (mach_task_self (), idport);
-             pthread_mutex_lock (&np->lock);
-             err = check_openmodes (np->nn, (flags & (O_RDWR|O_EXEC)), file);
-             if (!err)
+
+             if (np == dnp)
                {
-                 /* If the looked-up file carries a fake reference, we
-                    use that and clear the FAKE_REFERENCE flag.  */
-                 if (np->nn->faked & FAKE_REFERENCE)
-                   np->nn->faked &= ~FAKE_REFERENCE;
-                 else
-                   netfs_nref (np);
+                 /* dnp is already locked.  */
                }
-             pthread_mutex_unlock (&np->lock);
+             else
+               {
+                 pthread_mutex_lock (&np->lock);
+                 pthread_mutex_unlock (&dnp->lock);
+               }
+
+             /* If the looked-up file carries a fake reference, we
+                use that and clear the FAKE_REFERENCE flag.  */
+             if (np->nn->faked & FAKE_REFERENCE)
+               np->nn->faked &= ~FAKE_REFERENCE;
+             else
+               netfs_nref (np);
+
+             err = check_openmodes (np->nn, (flags & (O_RDWR|O_EXEC)), file);
              pthread_mutex_unlock (&idport_ihash_lock);
            }
          else
            {
              err = new_node (file, idport, 1, flags, &np);
+             pthread_mutex_unlock (&dnp->lock);
              if (!err)
-               {
-                 pthread_mutex_unlock (&np->lock);
-                 err = netfs_validate_stat (np, diruser->user);
-               }
+               err = netfs_validate_stat (np, diruser->user);
            }
        }
     }
   if (err)
-    return err;
+    goto lose;
 
   if (retry_name[0] == '\0' && *do_retry == FS_RETRY_NORMAL)
     flags &= ~(O_CREAT|O_EXCL|O_NOLINK|O_NOTRANS|O_NONBLOCK);
@@ -393,7 +402,9 @@ netfs_S_dir_lookup (struct protid *diruser,
        }
     }
 
-  netfs_nrele (np);
+ lose:
+  if (np != NULL)
+    netfs_nput (np);
   return err;
 }
 
-- 
1.7.10.4