From 4e48673172b012a06575e4f5b681d3554eded2e2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgzones@googlemail.com>
Date: Mon, 6 Jan 2020 15:27:23 +0100
Subject: [PATCH] selinux: add trigger for policy reload to refresh internal
 selabel cache

Reload the internal selabel cache automatically on SELinux policy reloads so non pid-1 daemons are participating.

Run the reload function `mac_selinux_reload()` not manually on daemon-reload, but rather pass it as callback to libselinux.
Trigger the callback prior usage of the systemd internal selabel cache by depleting the selinux netlink socket via `avc_netlink_check_nb()`.

Improves: a9dfac21ec85 ("core: reload SELinux label cache on daemon-reload")
Improves: #13363
(cherry picked from commit 61f3e897f13101f29fb8027e8839498a469ad58e)

Related: #1888912
---
 src/basic/selinux-util.c | 23 +++++++++++++++++++----
 src/basic/selinux-util.h |  1 -
 src/core/main.c          |  2 --
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/basic/selinux-util.c b/src/basic/selinux-util.c
index a078ce23ef..bfe3d015aa 100644
--- a/src/basic/selinux-util.c
+++ b/src/basic/selinux-util.c
@@ -10,6 +10,7 @@
 #include <syslog.h>
 
 #if HAVE_SELINUX
+#include <selinux/avc.h>
 #include <selinux/context.h>
 #include <selinux/label.h>
 #include <selinux/selinux.h>
@@ -32,6 +33,8 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(context_t, context_free);
 #define _cleanup_freecon_ _cleanup_(freeconp)
 #define _cleanup_context_free_ _cleanup_(context_freep)
 
+static int mac_selinux_reload(int seqno);
+
 static int cached_use = -1;
 static struct selabel_handle *label_hnd = NULL;
 
@@ -63,6 +66,8 @@ int mac_selinux_init(void) {
         usec_t before_timestamp, after_timestamp;
         struct mallinfo before_mallinfo, after_mallinfo;
 
+        selinux_set_callback(SELINUX_CB_POLICYLOAD, (union selinux_callback) mac_selinux_reload);
+
         if (label_hnd)
                 return 0;
 
@@ -105,13 +110,12 @@ void mac_selinux_finish(void) {
 #endif
 }
 
-void mac_selinux_reload(void) {
-
 #if HAVE_SELINUX
+static int mac_selinux_reload(int seqno) {
         struct selabel_handle *backup_label_hnd;
 
         if (!label_hnd)
-                return;
+                return 0;
 
         backup_label_hnd = TAKE_PTR(label_hnd);
 
@@ -122,8 +126,10 @@ void mac_selinux_reload(void) {
                 selabel_close(backup_label_hnd);
         else
                 label_hnd = backup_label_hnd;
-#endif
+
+        return 0;
 }
+#endif
 
 int mac_selinux_fix(const char *path, LabelFixFlags flags) {
 
@@ -152,6 +158,9 @@ int mac_selinux_fix(const char *path, LabelFixFlags flags) {
         if (fstat(fd, &st) < 0)
                 return -errno;
 
+        /* Check for policy reload so 'label_hnd' is kept up-to-date by callbacks */
+        (void) avc_netlink_check_nb();
+
         if (selabel_lookup_raw(label_hnd, &fcon, path, st.st_mode) < 0) {
                 r = -errno;
 
@@ -345,6 +354,9 @@ static int selinux_create_file_prepare_abspath(const char *abspath, mode_t mode)
         assert(abspath);
         assert(path_is_absolute(abspath));
 
+        /* Check for policy reload so 'label_hnd' is kept up-to-date by callbacks */
+        (void) avc_netlink_check_nb();
+
         r = selabel_lookup_raw(label_hnd, &filecon, abspath, mode);
         if (r < 0) {
                 /* No context specified by the policy? Proceed without setting it. */
@@ -496,6 +508,9 @@ int mac_selinux_bind(int fd, const struct sockaddr *addr, socklen_t addrlen) {
 
         path = strndupa(un->sun_path, addrlen - offsetof(struct sockaddr_un, sun_path));
 
+        /* Check for policy reload so 'label_hnd' is kept up-to-date by callbacks */
+        (void) avc_netlink_check_nb();
+
         if (path_is_absolute(path))
                 r = selabel_lookup_raw(label_hnd, &fcon, path, S_IFSOCK);
         else {
diff --git a/src/basic/selinux-util.h b/src/basic/selinux-util.h
index 639c35b687..bd5207c318 100644
--- a/src/basic/selinux-util.h
+++ b/src/basic/selinux-util.h
@@ -13,7 +13,6 @@ void mac_selinux_retest(void);
 
 int mac_selinux_init(void);
 void mac_selinux_finish(void);
-void mac_selinux_reload(void);
 
 int mac_selinux_fix(const char *path, LabelFixFlags flags);
 int mac_selinux_apply(const char *path, const char *label);
diff --git a/src/core/main.c b/src/core/main.c
index d5c41da0c4..d897155644 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1682,8 +1682,6 @@ static int invoke_main_loop(
                         saved_log_level = m->log_level_overridden ? log_get_max_level() : -1;
                         saved_log_target = m->log_target_overridden ? log_get_target() : _LOG_TARGET_INVALID;
 
-                        mac_selinux_reload();
-
                         (void) parse_configuration(saved_rlimit_nofile, saved_rlimit_memlock);
 
                         set_manager_defaults(m);