closefrom: Import some changes from sudo

Take most of the changes done in sudo, but preserve the existing local
changes and refactoring.

In addition, refactor pstat implementation into closefrom_pstat(), so
that the code is easier to read, and requires no conditional
declarations.

diff --git a/src/closefrom.c b/src/closefrom.c
index 962af79aca70d728064f7e1dfc6b948ac8f3b690..be38813a1984a6e7f8c84f817c01564552a8e0ed 100644 (file)
--- a/src/closefrom.c
+++ b/src/closefrom.c
@@ -1,6 +1,8 @@
 /*
- * Copyright (c) 2004-2005, 2007, 2010, 2012-2014
- *     Todd C. Miller <Todd.Miller@courtesan.com>
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2004-2005, 2007, 2010, 2012-2015, 2017-2018
+ *     Todd C. Miller <Todd.Miller@sudo.ws>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -17,19 +19,11 @@
 
 #include <config.h>
 
-#include <sys/types.h>
-#include <unistd.h>
-#include <stdio.h>
-#ifdef STDC_HEADERS
-# include <stdlib.h>
-# include <stddef.h>
-#else
-# ifdef HAVE_STDLIB_H
-#  include <stdlib.h>
-# endif
-#endif /* STDC_HEADERS */
+#include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <stdlib.h>
+#include <unistd.h>
 #ifdef HAVE_PSTAT_GETPROC
 # include <sys/param.h>
 # include <sys/pstat.h>
@@ -56,10 +50,6 @@
 # define OPEN_MAX 256
 #endif
 
-#if defined(HAVE_FCNTL_CLOSEM) && !defined(HAVE_DIRFD)
-# define closefrom     closefrom_fallback
-#endif
-
 static inline void
 closefrom_close(int fd)
 {
@@ -81,46 +71,46 @@ closefrom_fallback(int lowfd)
        long fd, maxfd;
 
        /*
-        * Fall back on sysconf() or getdtablesize().  We avoid checking
-        * resource limits since it is possible to open a file descriptor
-        * and then drop the rlimit such that it is below the open fd.
+        * Fall back on sysconf(_SC_OPEN_MAX) or getdtablesize(). This is
+        * equivalent to checking the RLIMIT_NOFILE soft limit. It is
+        * possible for there to be open file descriptors past this limit
+        * but there is not much we can do about that since the hard limit
+        * may be RLIM_INFINITY (LLONG_MAX or ULLONG_MAX on modern systems).
         */
 #ifdef HAVE_SYSCONF
        maxfd = sysconf(_SC_OPEN_MAX);
 #else
        maxfd = getdtablesize();
 #endif /* HAVE_SYSCONF */
-       if (maxfd < 0)
+       if (maxfd < OPEN_MAX)
                maxfd = OPEN_MAX;
 
+       /* Make sure we did not get RLIM_INFINITY as the upper limit. */
+       if (maxfd > INT_MAX)
+               maxfd = INT_MAX;
+
        for (fd = lowfd; fd < maxfd; fd++)
                closefrom_close(fd);
 }
 
-/*
- * Close all file descriptors greater than or equal to lowfd.
- * We try the fast way first, falling back on the slow method.
- */
-#if defined(HAVE_FCNTL_CLOSEM)
-void
-closefrom(int lowfd)
-{
-       if (fcntl(lowfd, F_CLOSEM, 0) == -1)
-               closefrom_fallback(lowfd);
-}
-#elif defined(HAVE_PSTAT_GETPROC)
-void
-closefrom(int lowfd)
+#if defined(HAVE_PSTAT_GETPROC)
+static int
+closefrom_pstat(int lowfd)
 {
-       struct pst_status pstat;
+       struct pst_status pst;
        int fd;
 
-       if (pstat_getproc(&pstat, sizeof(pstat), 0, getpid()) != -1) {
-               for (fd = lowfd; fd <= pstat.pst_highestfd; fd++)
+       /*
+        * EOVERFLOW is not a fatal error for the fields we use.
+        * See the "EOVERFLOW Error" section of pstat_getvminfo(3).
+        */
+       if (pstat_getproc(&pst, sizeof(pst), 0, getpid()) != -1 ||
+           errno == EOVERFLOW) {
+               for (fd = lowfd; fd <= pst.pst_highestfd; fd++)
                        (void)close(fd);
-       } else {
-               closefrom_fallback(lowfd);
+               return 0;
        }
+       return -1;
 }
 #elif defined(HAVE_DIRFD)
 static int
@@ -135,8 +125,8 @@ closefrom_procfs(int lowfd)
        int ret = 0;
        int i;
 
-       /* Use /proc/self/fd (or /dev/fd on FreeBSD) if it exists. */
-# if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__APPLE__)
+       /* Use /proc/self/fd (or /dev/fd on macOS) if it exists. */
+# ifdef __APPLE__
        path = "/dev/fd";
 # else
        path = "/proc/self/fd";
@@ -180,13 +170,28 @@ closefrom_procfs(int lowfd)
 
        return ret;
 }
+#endif
 
+/*
+ * Close all file descriptors greater than or equal to lowfd.
+ * We try the fast way first, falling back on the slow method.
+ */
 void
 closefrom(int lowfd)
 {
-       if (closefrom_procfs(lowfd) == 0)
+       /* Try the fast method first, if possible. */
+#if defined(HAVE_FCNTL_CLOSEM)
+       if (fcntl(lowfd, F_CLOSEM, 0) != -1)
+               return;
+#endif /* HAVE_FCNTL_CLOSEM */
+#if defined(HAVE_PSTAT_GETPROC)
+       if (closefrom_pstat(lowfd) != -1)
+               return;
+#elif defined(HAVE_DIRFD)
+       if (closefrom_procfs(lowfd) != -1)
                return;
+#endif /* HAVE_DIRFD */
 
+       /* Do things the slow way. */
        closefrom_fallback(lowfd);
 }
-#endif /* HAVE_FCNTL_CLOSEM */