xnu-3789.31.2.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 9cb8339bf59943b261f8ce4c8de547fc6589c21d..84960728d5a22739e99d7d089113688bc955556f 100644 (file)
--- a/bsd/kern/tty_tty.c
+++ b/bsd/kern/tty_tty.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997-2012 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 1997-2013 Apple Computer, Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
@@ -76,7 +76,6 @@
 /* Forward declarations for cdevsw[] entry */
 /* XXX we should consider making these static */
 int cttyopen(dev_t dev, int flag, int mode, proc_t p);
-int cttyclose(dev_t dev, int flag, int mode, proc_t p);
 int cttyread(dev_t dev, struct uio *uio, int flag);
 int cttywrite(dev_t dev, struct uio *uio, int flag);
 int cttyioctl(dev_t dev, u_long cmd, caddr_t addr, int flag, proc_t p);
@@ -86,65 +85,76 @@ static vnode_t cttyvp(proc_t p);
 int
 cttyopen(dev_t dev, int flag, __unused int mode, proc_t p)
 {
-       vnode_t ttyvp;
-       int error;
+       vnode_t ttyvp = cttyvp(p);
+       struct vfs_context context;
+       int error = 0;
+       int cttyflag, doclose = 0;
+       struct session *sessp;
 
-       /*
-        * A little hack--this device, used by many processes,
-        * does an open on another device, which can cause unhappiness
-        * if the second-level open blocks indefinitely (e.g. if the
-        * master side has hung up).  This driver doesn't care
-        * about serializing opens and closes, so drop the lock.
-        */
-       devsw_unlock(dev, S_IFCHR);
+       if (ttyvp == NULL)
+               return (ENXIO);
 
-       if ((ttyvp = cttyvp(p)) == NULL) {
-               error = ENXIO;
-       } else {
-               struct vfs_context context;
+       context.vc_thread = current_thread();
+       context.vc_ucred = kauth_cred_proc_ref(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. 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);
 
-               kauth_cred_unref(&context.vc_ucred);
-               vnode_put(ttyvp);
+               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);
 
-       devsw_lock(dev, S_IFCHR);
-       return (error);
-}
-
-/*
- * This driver is marked D_TRACKCLOSE and so gets a close
- * for every open so that ttyvp->v_specinfo->si_count can be kept sane.
- */
-int
-cttyclose(dev_t dev, int flag, __unused int mode, proc_t p)
-{
-       vnode_t ttyvp;
-       int error;
-
-       /* See locking commentary above. */
-
-       devsw_unlock(dev, S_IFCHR);
-
-       if ((ttyvp = cttyvp(p)) == NULL) {
-               error = ENXIO;
-       } else {
-               struct vfs_context context;
-
-               context.vc_thread = current_thread();
-               context.vc_ucred = kauth_cred_proc_ref(p);
-
-               error = VNOP_CLOSE(ttyvp, flag, &context);
-
-               kauth_cred_unref(&context.vc_ucred);
-               vnode_put(ttyvp);
-       }
+       vnode_put(ttyvp);
+       kauth_cred_unref(&context.vc_ucred);
 
-       devsw_lock(dev, S_IFCHR);
        return (error);
 }