libnss_tcb: Drop use of readdir_r(3).

In commit 72ef702 we introduced a
replacement for the deprecated readdir_r(3) by using readdir(3) with
global thread-local storage.  As almost any operating system released
within the last eight years supports thread-local storage natively,
there is little to no reason keeping the potentially dangerous
fallback to readdir_r(3).

Signed-off-by: Björn Esser <[email protected]>

Author: besser82

ChangeLog

@@ -19,6 +19,15 @@
 	* progs/Makefile: Likewise.
 	* LICENSE: Update copyright for this contribution.
 
+	libnss_tcb: Drop use of readdir_r(3).
+	In commit 72ef702a886c8a9749bdc01d89a57cdf0455318c we introduced a
+	replacment for the deprecated readdir_r(3) by using readdir(3) with
+	global thread-local storage.  As almost any operating system released
+	within the last eight years supports thread-local storage natively,
+	there is little to no reason keeping the potentially dangerous
+	fallback to readdir_r(3).
+	* libs/nss.c (_nss_tcb_getspnam_r): Drop use of readdir_r(3).
+
 2024-10-17  Dmitry V. Levin  <ldv at owl.openwall.com>
 
 	pam_tcb: Do not use deprecated _pam_overwrite macro.

libs/nss.c

@@ -11,18 +11,7 @@
 
 #include "tcb.h"
 
-/* readdir_r(3) is deprecated since glibc 2.24 */
-#if defined __GLIBC_PREREQ && __GLIBC_PREREQ(2, 24)
-#define USE_READDIR 1
-#else
-#define USE_READDIR 0
-#endif
-
-#if USE_READDIR
 static __thread DIR *tcbdir = NULL;
-#else
-static DIR *tcbdir = NULL;
-#endif
 
 int _nss_tcb_setspent(void)
 {
@@ -107,9 +96,6 @@ int _nss_tcb_getspnam_r(const char *name, struct spwd *__result_buf,
 int _nss_tcb_getspent_r(struct spwd *__result_buf,
     char *__buffer, size_t __buflen, struct spwd **__result)
 {
-#if !USE_READDIR
-	struct dirent entry;
-#endif
 	struct dirent *result;
 	off_t currpos;
 	int retval, saved_errno;
@@ -122,15 +108,10 @@ int _nss_tcb_getspent_r(struct spwd *__result_buf,
 
 	do {
 		currpos = telldir(tcbdir);
-#if USE_READDIR
 		saved_errno = errno;
 		errno = 0;
 		result = readdir(tcbdir);
 		if (!result && errno) {
-#else
-		if (readdir_r(tcbdir, &entry, &result)) {
-			saved_errno = errno;
-#endif
 			closedir(tcbdir);
 			errno = saved_errno;
 			tcbdir = NULL;
@@ -142,9 +123,7 @@ int _nss_tcb_getspent_r(struct spwd *__result_buf,
 			tcbdir = NULL;
 			return NSS_STATUS_NOTFOUND;
 		}
-#if USE_READDIR
 		errno = saved_errno;
-#endif
 	} while (!strcmp(result->d_name, ".") ||
 	    !strcmp(result->d_name, "..") || result->d_name[0] == ':');