* login/utmp_file.c (file_writable): New variable.

	(setutent_file): Don't try to open file for writing.
	(pututline_file): Before writing, make descriptor writable if
	necessary.

ChangeLog

@@ -1,3 +1,10 @@
+2008-11-29  Ulrich Drepper  <drepper@redhat.com>
+
+	* login/utmp_file.c (file_writable): New variable.
+	(setutent_file): Don't try to open file for writing.
+	(pututline_file): Before writing, make descriptor writable if
+	necessary.
+
 2008-11-26  Ulrich Drepper  <drepper@redhat.com>
 
 	* sysdeps/posix/getaddrinfo.c (getaddrinfo): Only restrict search

login/utmp_file.c

@@ -36,6 +36,7 @@
 
 /* Descriptor for the file and position.  */
 static int file_fd = -1;
+static bool file_writable;
 static off64_t file_offset;
 
 /* Cache for the last read entry.  */
@@ -138,7 +139,6 @@ setutent_file (void)
   if (file_fd < 0)
     {
       const char *file_name;
-      int result;
 
       file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
 
@@ -147,22 +147,18 @@ setutent_file (void)
 #else
 # define O_flags O_LARGEFILE
 #endif
-      file_fd = open_not_cancel_2 (file_name, O_RDWR | O_flags);
+      file_writable = false;
+      file_fd = open_not_cancel_2 (file_name, O_RDONLY | O_flags);
       if (file_fd == -1)
-	{
-	  /* Hhm, read-write access did not work.  Try read-only.  */
-	  file_fd = open_not_cancel_2 (file_name, O_RDONLY | O_flags);
-	  if (file_fd == -1)
-	    return 0;
-	}
+	return 0;
 
 #ifndef __ASSUME_O_CLOEXEC
 # ifdef O_CLOEXEC
       if (__have_o_cloexec <= 0)
 # endif
 	{
 	  /* We have to make sure the file is `closed on exec'.  */
-	  result = fcntl_not_cancel (file_fd, F_GETFD, 0);
+	  int result = fcntl_not_cancel (file_fd, F_GETFD, 0);
 	  if (result >= 0)
 	    {
 # ifdef O_CLOEXEC
@@ -404,6 +400,52 @@ pututline_file (const struct utmp *data)
 
   assert (file_fd >= 0);
 
+  if (! file_writable)
+    {
+      /* We must make the file descriptor writable before going on.  */
+      const char *file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
+
+      int new_fd = open_not_cancel_2 (file_name, O_RDWR | O_flags);
+      if (new_fd == -1)
+	return NULL;
+
+#ifndef __ASSUME_O_CLOEXEC
+# ifdef O_CLOEXEC
+      if (__have_o_cloexec <= 0)
+# endif
+	{
+	  /* We have to make sure the file is `closed on exec'.  */
+	  int result = fcntl_not_cancel (file_fd, F_GETFD, 0);
+	  if (result >= 0)
+	    {
+# ifdef O_CLOEXEC
+	      if (__have_o_cloexec == 0)
+		__have_o_cloexec = (result & FD_CLOEXEC) ? 1 : -1;
+
+	      if (__have_o_cloexec < 0)
+# endif
+		result = fcntl_not_cancel (file_fd, F_SETFD,
+					   result | FD_CLOEXEC);
+	    }
+
+	  if (result == -1)
+	    {
+	      close_not_cancel_no_status (file_fd);
+	      return NULL;
+	    }
+	}
+#endif
+
+      if (__lseek64 (new_fd, __lseek64 (file_fd, 0, SEEK_CUR), SEEK_SET) == -1
+	  || dup2 (new_fd, file_fd) < 0)
+	{
+	  close_not_cancel_no_status (new_fd);
+	  return NULL;
+	}
+      close_not_cancel_no_status (new_fd);
+      file_writable = true;
+    }
+
   /* Find the correct place to insert the data.  */
   if (file_offset > 0
       && (