X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/2d21ac55c334faf3a56e5634905ed6987fc787d4..d9a64523371fa019c4575bb400cbbc3a50ac9903:/bsd/kern/tty_tty.c

diff --git a/bsd/kern/tty_tty.c b/bsd/kern/tty_tty.c
index 1c9882d96..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@
  * 
@@ -82,13 +82,14 @@ int cttyioctl(dev_t dev, u_long cmd, caddr_t addr, int flag, proc_t p);
 int cttyselect(dev_t dev, int flag, void* wql, proc_t p);
 static vnode_t cttyvp(proc_t p);
 
-
 int
-cttyopen(__unused dev_t dev, int flag, __unused int mode, proc_t p)
+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);
@@ -96,7 +97,61 @@ cttyopen(__unused dev_t dev, int flag, __unused int mode, proc_t p)
 	context.vc_thread = current_thread();
 	context.vc_ucred = kauth_cred_proc_ref(p);
 
-	error = VNOP_OPEN(ttyvp, flag, &context);
+	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. To avoid opencount leak,
+	 * open the vnode only for the first time. 
+	 */
+	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);
 
@@ -158,7 +213,7 @@ cttyioctl(__unused dev_t dev, u_long cmd, caddr_t addr, int flag, proc_t p)
 	if (cmd == TIOCNOTTY) {
 		sessp = proc_session(p);
 		if (!SESS_LEADER(p, sessp)) {
-			OSBitAndAtomic(~((uint32_t)P_CONTROLT), (UInt32 *)&p->p_flag);
+			OSBitAndAtomic(~((uint32_t)P_CONTROLT), &p->p_flag);
 			if (sessp != SESSION_NULL)
 				session_rele(sessp);
 			error = 0;