X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/6d2010ae8f7a6078e10b361c6962983bab233e0f..d9a64523371fa019c4575bb400cbbc3a50ac9903:/bsd/kern/tty_tty.c

diff --git a/bsd/kern/tty_tty.c b/bsd/kern/tty_tty.c
index ec7bee445..84960728d 100644
--- 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);