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

2 files changed, 26 insertions, 28 deletions

diff --git a/lib/libc/gen/directory.3 b/lib/libc/gen/directory.3
index 4573d45..1e864f8 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 4954b97..d72b500 100644
--- a/lib/libc/gen/telldir.c
+++ b/lib/libc/gen/telldir.c
@@ -47,13 +47,6 @@ __FBSDID("$FreeBSD$");
 #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
  */
 long
@@ -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
 }
 
 /*