From 18ae4fcc470e6f316195f916997df072c3335da3 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Tue, 29 Jul 2014 00:16:33 +0000
Subject: [PATCH] If telldir() is called immediately after a call to seekdir(),
 POSIX requires the return value of telldir() to equal the value passed to
 seekdir().  The current seekdir code with SINGLEUSE enabled breaks this case
 as each call to telldir() allocates a new cookie.  Instead, remove the
 SINGLEUSE code and change telldir() to look for an existing cookie for the
 directory's current location rather than always creating a new cookie.

CR:		https://phabric.freebsd.org/D490
PR:		121656
Reviewed by:	jilles
MFC after:	1 week
---
 lib/libc/gen/directory.3 | 13 +++++--------
 lib/libc/gen/telldir.c   | 41 ++++++++++++++++++++--------------------
 2 files changed, 26 insertions(+), 28 deletions(-)

diff --git a/lib/libc/gen/directory.3 b/lib/libc/gen/directory.3
index 4573d4513fe2..1e864f8dcbc5 100644
--- a/lib/libc/gen/directory.3
+++ b/lib/libc/gen/directory.3
@@ -28,7 +28,7 @@
 .\"     @(#)directory.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd August 18, 2013
+.Dd July 28, 2014
 .Dt DIRECTORY 3
 .Os
 .Sh NAME
@@ -169,6 +169,10 @@ If the directory is closed and then
 reopened, prior values returned by
 .Fn telldir
 will no longer be valid.
+Values returned by
+.Fn telldir
+are also invalidated by a call to
+.Fn rewinddir .
 .Pp
 The
 .Fn seekdir
@@ -182,13 +186,6 @@ The new position reverts to the one associated with the
 when the
 .Fn telldir
 operation was performed.
-State associated with the token returned by
-.Fn telldir is freed when it is passed to
-.Fn seekdir .
-If you wish return to the same location again,
-then you must create a new token with another
-.Fn telldir
-call.
 .Pp
 The
 .Fn rewinddir
diff --git a/lib/libc/gen/telldir.c b/lib/libc/gen/telldir.c
index 4954b973a915..d72b500b051c 100644
--- a/lib/libc/gen/telldir.c
+++ b/lib/libc/gen/telldir.c
@@ -46,13 +46,6 @@ __FBSDID("$FreeBSD$");
 #include "gen-private.h"
 #include "telldir.h"
 
-/*
- * The option SINGLEUSE may be defined to say that a telldir
- * cookie may be used only once before it is freed. This option
- * is used to avoid having memory usage grow without bound.
- */
-#define SINGLEUSE
-
 /*
  * return a pointer into a directory
  */
@@ -61,18 +54,31 @@ telldir(dirp)
 	DIR *dirp;
 {
 	struct ddloc *lp;
+	long idx;
 
-	if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
-		return (-1);
 	if (__isthreaded)
 		_pthread_mutex_lock(&dirp->dd_lock);
-	lp->loc_index = dirp->dd_td->td_loccnt++;
-	lp->loc_seek = dirp->dd_seek;
-	lp->loc_loc = dirp->dd_loc;
-	LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
+	LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) {
+		if (lp->loc_seek == dirp->dd_seek &&
+		    lp->loc_loc == dirp->dd_loc)
+			break;
+	}
+	if (lp == NULL) {
+		lp = malloc(sizeof(struct ddloc));
+		if (lp == NULL) {
+			if (__isthreaded)
+				_pthread_mutex_unlock(&dirp->dd_lock);
+			return (-1);
+		}
+		lp->loc_index = dirp->dd_td->td_loccnt++;
+		lp->loc_seek = dirp->dd_seek;
+		lp->loc_loc = dirp->dd_loc;
+		LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe);
+	}
+	idx = lp->loc_index;
 	if (__isthreaded)
 		_pthread_mutex_unlock(&dirp->dd_lock);
-	return (lp->loc_index);
+	return (idx);
 }
 
 /*
@@ -94,7 +100,7 @@ _seekdir(dirp, loc)
 	if (lp == NULL)
 		return;
 	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
-		goto found;
+		return;
 	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
 	dirp->dd_seek = lp->loc_seek;
 	dirp->dd_loc = 0;
@@ -103,11 +109,6 @@ _seekdir(dirp, loc)
 		if (dp == NULL)
 			break;
 	}
-found:
-#ifdef SINGLEUSE
-	LIST_REMOVE(lp, loc_lqe);
-	free((caddr_t)lp);
-#endif
 }
 
 /*