This patch will upgrade Sudo version 1.8.31 to Sudo version 1.8.31
patchlevel 1.  To apply:

    $ cd sudo-1.8.31
    $ patch -p1 < sudo-1.8.31p1.patch

diff -urNa sudo-1.8.31/ChangeLog sudo-1.8.31p1/ChangeLog
--- sudo-1.8.31/ChangeLog	Thu Jan 30 05:56:19 2020
+++ sudo-1.8.31p1/ChangeLog	Sat Mar 14 11:25:43 2020
@@ -1,8 +1,25 @@
+2020-03-14  Todd C. Miller  <Todd.Miller@sudo.ws>
+
+	* .hgtags:
+	Added tag SUDO_1_8_31p1 for changeset c80864e62917
+	[ec1850cd11a2] [tip] <1.8>
+
+	* NEWS, configure, configure.ac:
+	Sudo 1.8.31p1
+	[c80864e62917] [SUDO_1_8_31p1] <1.8>
+
+	* src/limits.c:
+	Ignore a failure to restore the RLIMIT_CORE resource limit. Linux
+	containers don't allow RLIMIT_CORE to be set back to RLIM_INFINITY
+	if we set the limit to zero, even for root. This is not a problem
+	outside the container.
+	[314df33eea97] <1.8>
+
 2020-01-30  Todd C. Miller  <Todd.Miller@sudo.ws>
 
 	* .hgtags:
 	Added tag SUDO_1_8_31 for changeset d14f7d0f6174
-	[57a9df806149] [tip] <1.8>
+	[57a9df806149] <1.8>
 
 	* configure, configure.ac, doc/LICENSE:
 	Sudo 1.8.31
diff -urNa sudo-1.8.31/NEWS sudo-1.8.31p1/NEWS
--- sudo-1.8.31/NEWS	Thu Jan 30 05:51:46 2020
+++ sudo-1.8.31p1/NEWS	Sat Mar 14 11:22:49 2020
@@ -1,3 +1,11 @@
+What's new in Sudo 1.8.31p1
+
+ * Sudo once again ignores a failure to restore the RLIMIT_CORE
+   resource limit, as it did prior to version 1.8.29.  Linux
+   containers don't allow RLIMIT_CORE to be set back to RLIM_INFINITY
+   if we set the limit to zero, even for root, which resulted in a
+   warning from sudo.
+
 What's new in Sudo 1.8.31
 
  * Fixed CVE-2019-18634, a buffer overflow when the "pwfeedback"
diff -urNa sudo-1.8.31/configure sudo-1.8.31p1/configure
--- sudo-1.8.31/configure	Thu Jan 30 05:52:43 2020
+++ sudo-1.8.31p1/configure	Sat Mar 14 11:20:30 2020
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.69 for sudo 1.8.31.
+# Generated by GNU Autoconf 2.69 for sudo 1.8.31p1.
 #
 # Report bugs to <https://bugzilla.sudo.ws/>.
 #
@@ -590,8 +590,8 @@
 # Identity of this package.
 PACKAGE_NAME='sudo'
 PACKAGE_TARNAME='sudo'
-PACKAGE_VERSION='1.8.31'
-PACKAGE_STRING='sudo 1.8.31'
+PACKAGE_VERSION='1.8.31p1'
+PACKAGE_STRING='sudo 1.8.31p1'
 PACKAGE_BUGREPORT='https://bugzilla.sudo.ws/'
 PACKAGE_URL=''
 
@@ -1544,7 +1544,7 @@
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures sudo 1.8.31 to adapt to many kinds of systems.
+\`configure' configures sudo 1.8.31p1 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1609,7 +1609,7 @@
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of sudo 1.8.31:";;
+     short | recursive ) echo "Configuration of sudo 1.8.31p1:";;
    esac
   cat <<\_ACEOF
 
@@ -1875,7 +1875,7 @@
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-sudo configure 1.8.31
+sudo configure 1.8.31p1
 generated by GNU Autoconf 2.69
 
 Copyright (C) 2012 Free Software Foundation, Inc.
@@ -2584,7 +2584,7 @@
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by sudo $as_me 1.8.31, which was
+It was created by sudo $as_me 1.8.31p1, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   $ $0 $@
@@ -27543,7 +27543,7 @@
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by sudo $as_me 1.8.31, which was
+This file was extended by sudo $as_me 1.8.31p1, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -27609,7 +27609,7 @@
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
-sudo config.status 1.8.31
+sudo config.status 1.8.31p1
 configured by $0, generated by GNU Autoconf 2.69,
   with options \\"\$ac_cs_config\\"
 
diff -urNa sudo-1.8.31/configure.ac sudo-1.8.31p1/configure.ac
--- sudo-1.8.31/configure.ac	Thu Jan 30 05:52:13 2020
+++ sudo-1.8.31p1/configure.ac	Sat Mar 14 11:20:07 2020
@@ -18,7 +18,7 @@
 dnl OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 dnl
 AC_PREREQ([2.59])
-AC_INIT([sudo], [1.8.31], [https://bugzilla.sudo.ws/], [sudo])
+AC_INIT([sudo], [1.8.31p1], [https://bugzilla.sudo.ws/], [sudo])
 AC_CONFIG_HEADER([config.h pathnames.h])
 AC_CONFIG_SRCDIR([src/sudo.c])
 dnl
diff -urNa sudo-1.8.31/src/limits.c sudo-1.8.31p1/src/limits.c
--- sudo-1.8.31/src/limits.c	Wed Dec 25 19:16:37 2019
+++ sudo-1.8.31p1/src/limits.c	Sat Mar 14 11:19:52 2020
@@ -114,13 +114,21 @@
 
     if (getrlimit(RLIMIT_CORE, &corelimit) == -1)
 	sudo_warn("getrlimit(RLIMIT_CORE)");
+    sudo_debug_printf(SUDO_DEBUG_INFO, "RLIMIT_CORE [%lld, %lld] -> [0, 0]",
+	(long long)corelimit.rlim_cur, (long long)corelimit.rlim_max);
     if (setrlimit(RLIMIT_CORE, &rl) == -1)
 	sudo_warn("setrlimit(RLIMIT_CORE)");
 #ifdef __linux__
     /* On Linux, also set PR_SET_DUMPABLE to zero (reset by execve). */
-    if ((dumpflag = prctl(PR_GET_DUMPABLE, 0, 0, 0, 0)) == -1)
+    if ((dumpflag = prctl(PR_GET_DUMPABLE, 0, 0, 0, 0)) == -1) {
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+	    "prctl(PR_GET_DUMPABLE, 0, 0, 0, 0)");
 	dumpflag = 0;
-    (void) prctl(PR_SET_DUMPABLE, 0, 0, 0, 0);
+    }
+    if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) {
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+	    "prctl(PR_SET_DUMPABLE, %d, 0, 0, 0)", dumpflag);
+    }
 #endif /* __linux__ */
     coredump_disabled = true;
 
@@ -136,10 +144,20 @@
     debug_decl(restore_coredump, SUDO_DEBUG_UTIL)
 
     if (coredump_disabled) {
-	if (setrlimit(RLIMIT_CORE, &corelimit) == -1)
-	    sudo_warn("setrlimit(RLIMIT_CORE)");
+	/*
+	 * Linux containers don't allow RLIMIT_CORE to be set back to
+	 * RLIM_INFINITY if we set the limit to zero, even for root.
+	 */
+	if (setrlimit(RLIMIT_CORE, &corelimit) == -1) {
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"setrlimit(RLIMIT_CORE, [%lld, %lld])",
+		(long long)corelimit.rlim_cur, (long long)corelimit.rlim_max);
+	}
 #ifdef __linux__
-	(void) prctl(PR_SET_DUMPABLE, dumpflag, 0, 0, 0);
+	if (prctl(PR_SET_DUMPABLE, dumpflag, 0, 0, 0) == -1) {
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"prctl(PR_SET_DUMPABLE, %d, 0, 0, 0)", dumpflag);
+	}
 #endif /* __linux__ */
     }
     debug_return;
@@ -162,8 +180,14 @@
 
     if (getrlimit(RLIMIT_NPROC, &nproclimit) != 0)
 	sudo_warn("getrlimit(RLIMIT_NPROC)");
+    sudo_debug_printf(SUDO_DEBUG_INFO, "RLIMIT_NPROC [%lld, %lld] -> [inf, inf]",
+	(long long)nproclimit.rlim_cur, (long long)nproclimit.rlim_max);
     if (setrlimit(RLIMIT_NPROC, &rl) == -1) {
 	rl.rlim_cur = rl.rlim_max = nproclimit.rlim_max;
+	sudo_debug_printf(SUDO_DEBUG_INFO,
+	    "RLIMIT_NPROC [%lld, %lld] -> [%lld, %lld]",
+	    (long long)nproclimit.rlim_cur, (long long)nproclimit.rlim_max,
+	    (long long)rl.rlim_cur, (long long)rl.rlim_max);
 	if (setrlimit(RLIMIT_NPROC, &rl) != 0)
 	    sudo_warn("setrlimit(RLIMIT_NPROC)");
     }
@@ -180,8 +204,11 @@
 #ifdef __linux__
     debug_decl(restore_nproc, SUDO_DEBUG_UTIL)
 
-    if (setrlimit(RLIMIT_NPROC, &nproclimit) != 0)
-	sudo_warn("setrlimit(RLIMIT_NPROC)");
+    if (setrlimit(RLIMIT_NPROC, &nproclimit) != 0) {
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+	    "setrlimit(RLIMIT_NPROC, [%lld, %lld])",
+	    (long long)nproclimit.rlim_cur, (long long)nproclimit.rlim_max);
+    }
 
     debug_return;
 #endif /* __linux__ */
@@ -203,6 +230,11 @@
 	struct saved_limit *lim = &saved_limits[idx];
 	if (getrlimit(lim->resource, &lim->oldlimit) == -1)
 	    continue;
+	sudo_debug_printf(SUDO_DEBUG_INFO,
+	    "getrlimit(lim->name) -> [%lld, %lld]",
+	    (long long)lim->oldlimit.rlim_cur,
+	    (long long)lim->oldlimit.rlim_max);
+
 	lim->saved = true;
 	if (lim->newlimit.rlim_cur != RLIM_INFINITY) {
 	    /* Don't reduce the soft resource limit. */
@@ -217,13 +249,28 @@
 		lim->newlimit.rlim_max = lim->oldlimit.rlim_max;
 	}
 	if ((rc = setrlimit(lim->resource, &lim->newlimit)) == -1) {
-	    if (lim->fallback != NULL)
-		rc = setrlimit(lim->resource, lim->fallback);
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"setrlimit(%s, [%lld, %lld])", lim->name,
+		(long long)lim->newlimit.rlim_cur,
+		(long long)lim->newlimit.rlim_max);
+	    if (lim->fallback != NULL) {
+		if ((rc = setrlimit(lim->resource, lim->fallback)) == -1) {
+		    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+			"setrlimit(%s, [%lld, %lld])", lim->name,
+			(long long)lim->fallback->rlim_cur,
+			(long long)lim->fallback->rlim_max);
+		}
+	    }
 	    if (rc == -1) {
 		/* Try setting new rlim_cur to old rlim_max. */
 		lim->newlimit.rlim_cur = lim->oldlimit.rlim_max;
 		lim->newlimit.rlim_max = lim->oldlimit.rlim_max;
-		rc = setrlimit(lim->resource, &lim->newlimit);
+		if ((rc = setrlimit(lim->resource, &lim->newlimit)) == -1) {
+		    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+			"setrlimit(%s, [%lld, %lld])", lim->name,
+			(long long)lim->newlimit.rlim_cur,
+			(long long)lim->newlimit.rlim_max);
+		}
 	    }
 	    if (rc == -1)
 		sudo_warn("setrlimit(%s)", lim->name);
@@ -253,6 +300,10 @@
 		rc = setrlimit(lim->resource, &rl);
 		if (rc != -1 || errno != EINVAL)
 		    break;
+
+		sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		    "setrlimit(%s, [%lld, %lld])", lim->name,
+		    (long long)rl.rlim_cur, (long long)rl.rlim_max);
 
 		/*
 		 * Soft limit could be lower than current resource usage.