xnu-4903.221.2.tar.gz

[apple/xnu.git] / bsd / kern / tty_tty.c

diff --git a/bsd/kern/tty_tty.c b/bsd/kern/tty_tty.c
index ec7bee44581c5c532a900866909200d716b5fe66..84960728d5a22739e99d7d089113688bc955556f 100644 (file)
--- a/bsd/kern/tty_tty.c
+++ b/bsd/kern/tty_tty.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997-2006 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 1997-2013 Apple Computer, Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
@@ -87,7 +87,9 @@ cttyopen(dev_t dev, int flag, __unused int mode, proc_t p)
 {
        vnode_t ttyvp = cttyvp(p);
        struct vfs_context context;
-       int error;
+       int error = 0;
+       int cttyflag, doclose = 0;
+       struct session *sessp;
 
        if (ttyvp == NULL)
                return (ENXIO);
@@ -95,17 +97,60 @@ cttyopen(dev_t dev, int flag, __unused int mode, proc_t p)
        context.vc_thread = current_thread();
        context.vc_ucred = kauth_cred_proc_ref(p);
 
+       sessp = proc_session(p);
+       session_lock(sessp);
+       cttyflag = sessp->s_flags & S_CTTYREF;  
+       session_unlock(sessp);
+
        /*
         * A little hack--this device, used by many processes,
         * happens to do an open on another device, which can 
         * cause unhappiness if the second-level open blocks indefinitely 
         * (as could be the case if the master side has hung up).  Since
         * we know that this driver doesn't care about the serializing
-        * opens and closes, we can drop the lock.
+        * opens and closes, we can drop the lock. To avoid opencount leak,
+        * open the vnode only for the first time. 
         */
-       devsw_unlock(dev, S_IFCHR);
-       error = VNOP_OPEN(ttyvp, flag, &context);
-       devsw_lock(dev, S_IFCHR);
+       if (cttyflag == 0) {
+               devsw_unlock(dev, S_IFCHR);
+               error = VNOP_OPEN(ttyvp, flag, &context);
+               devsw_lock(dev, S_IFCHR);
+
+               if (error) 
+                       goto out;
+       
+               /*
+                * If S_CTTYREF is set, some other thread did an open
+                * and was able to set the flag, now perform a close, else
+                * set the flag.
+                */
+               session_lock(sessp);
+               if (cttyflag == (sessp->s_flags & S_CTTYREF))
+                       sessp->s_flags |= S_CTTYREF;
+               else
+                       doclose = 1;
+               session_unlock(sessp);
+
+               /*
+                * We have to take a reference here to make sure a close
+                * gets called during revoke. Note that once a controlling 
+                * tty gets opened by this driver, the only way close will
+                * get called is when the session leader , whose controlling
+                * tty is ttyvp, exits and vnode is revoked. We cannot 
+                * redirect close from this driver because underlying controlling
+                * terminal might change and close may get redirected to a 
+                * wrong vnode causing panic.
+                */
+               if (doclose) {
+                       devsw_unlock(dev, S_IFCHR);
+                       VNOP_CLOSE(ttyvp, flag, &context);
+                       devsw_lock(dev, S_IFCHR);
+               } else {
+                       error = vnode_ref(ttyvp);
+               }
+       }
+out:
+       session_rele(sessp);
 
        vnode_put(ttyvp);
        kauth_cred_unref(&context.vc_ucred);