diff --git a/Documentation/networking/ppp_generic.txt b/Documentation/networking/ppp_generic.txt
index 091d20273dcbbce70c75d1c1de76af25e100e344..61daf4b39600917a3baec3d9e200047f0831493a 100644
--- a/Documentation/networking/ppp_generic.txt
+++ b/Documentation/networking/ppp_generic.txt
@@ -300,12 +300,6 @@ unattached instance are:
 The ioctl calls available on an instance of /dev/ppp attached to a
 channel are:
 
-* PPPIOCDETACH detaches the instance from the channel.  This ioctl is
-  deprecated since the same effect can be achieved by closing the
-  instance.  In order to prevent possible races this ioctl will fail
-  with an EINVAL error if more than one file descriptor refers to this
-  instance (i.e. as a result of dup(), dup2() or fork()).
-
 * PPPIOCCONNECT connects this channel to a PPP interface.  The
   argument should point to an int containing the interface unit
   number.  It will return an EINVAL error if the channel is already
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index dc7c7ec432023a7ac8e7a63410f7ec04437ea7b7..02ad03a2fab773cd36707e50434cc559fc639f7c 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -605,30 +605,13 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 	if (cmd == PPPIOCDETACH) {
 		/*
-		 * We have to be careful here... if the file descriptor
-		 * has been dup'd, we could have another process in the
-		 * middle of a poll using the same file *, so we had
-		 * better not free the interface data structures -
-		 * instead we fail the ioctl.  Even in this case, we
-		 * shut down the interface if we are the owner of it.
-		 * Actually, we should get rid of PPPIOCDETACH, userland
-		 * (i.e. pppd) could achieve the same effect by closing
-		 * this fd and reopening /dev/ppp.
+		 * PPPIOCDETACH is no longer supported as it was heavily broken,
+		 * and is only known to have been used by pppd older than
+		 * ppp-2.4.2 (released November 2003).
 		 */
+		pr_warn_once("%s (%d) used obsolete PPPIOCDETACH ioctl\n",
+			     current->comm, current->pid);
 		err = -EINVAL;
-		if (pf->kind == INTERFACE) {
-			ppp = PF_TO_PPP(pf);
-			rtnl_lock();
-			if (file == ppp->owner)
-				unregister_netdevice(ppp->dev);
-			rtnl_unlock();
-		}
-		if (atomic_long_read(&file->f_count) < 2) {
-			ppp_release(NULL, file);
-			err = 0;
-		} else
-			pr_warn("PPPIOCDETACH file->f_count=%ld\n",
-				atomic_long_read(&file->f_count));
 		goto out;
 	}
 
diff --git a/include/uapi/linux/ppp-ioctl.h b/include/uapi/linux/ppp-ioctl.h
index b19a9c249b156f5877a0e8651a1d4d2330f6088d..784c2e3e572e013a24aeabf96ef400f453ffb72e 100644
--- a/include/uapi/linux/ppp-ioctl.h
+++ b/include/uapi/linux/ppp-ioctl.h
@@ -106,7 +106,7 @@ struct pppol2tp_ioc_stats {
 #define PPPIOCGIDLE	_IOR('t', 63, struct ppp_idle) /* get idle time */
 #define PPPIOCNEWUNIT	_IOWR('t', 62, int)	/* create new ppp unit */
 #define PPPIOCATTACH	_IOW('t', 61, int)	/* attach to ppp unit */
-#define PPPIOCDETACH	_IOW('t', 60, int)	/* detach from ppp unit/chan */
+#define PPPIOCDETACH	_IOW('t', 60, int)	/* obsolete, do not use */
 #define PPPIOCSMRRU	_IOW('t', 59, int)	/* set multilink MRU */
 #define PPPIOCCONNECT	_IOW('t', 58, int)	/* connect channel to unit */
 #define PPPIOCDISCONN	_IO('t', 57)		/* disconnect channel */