In the plugin registers with the debug framework at open time, the

sudo front-end will now set the default debug instance appropriately
before calling into the plugin.  This means the plugin no longer needs
to do the sudo_debug_set_default_instance() dance.

lib/util/sudo_conf.c

@@ -338,7 +338,6 @@ set_debugging(const char *conf_file)
     struct plugin_info *plugin_info;
     const char *progname;
     size_t prognamelen;
-    int instance;
     debug_decl(main, SUDO_DEBUG_UTIL, SUDO_DEBUG_INSTANCE_DEFAULT)
 
     progname = getprogname();
@@ -352,10 +351,7 @@ set_debugging(const char *conf_file)
 	     * Register debug instance for the main program, making it
 	     * the default instance if one is not already set.
 	     */
-	    instance = sudo_debug_register(progname, NULL, NULL,
+	    sudo_debug_register(progname, NULL, NULL, &debug_spec->debug_files);
-		&debug_spec->debug_files);
-	    if (sudo_debug_get_default_instance() == SUDO_DEBUG_INSTANCE_INITIALIZER)
-		sudo_debug_set_default_instance(instance);
 	    sudo_debug_enter(__func__, __FILE__, __LINE__, sudo_debug_subsys);
 	    continue;
 	}

lib/util/sudo_debug.c

@@ -310,6 +310,10 @@ sudo_debug_register(const char *program, const char *const subsystems[],
 	    SLIST_INSERT_HEAD(&instance->outputs, output, entries);
     }
 
+    /* Set default instance if not already set. */
+    if (sudo_debug_default_instance == -1)
+	sudo_debug_default_instance = idx;
+
     /* Stash the pid string so we only have to format it once. */
     if (sudo_debug_pidlen == 0) {
 	(void)snprintf(sudo_debug_pidstr, sizeof(sudo_debug_pidstr), "[%d] ",

plugins/sudoers/iolog.c

@@ -573,7 +573,7 @@ sudoers_io_open(unsigned int version, sudo_conv_t conversation,
     char * const *cur;
     const char *plugin_path = NULL;
     size_t len;
-    int i, prev_instance, rval = -1;
+    int i, rval = -1;
     debug_decl(sudoers_io_open, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
     sudo_conv = conversation;
@@ -583,8 +583,6 @@ sudoers_io_open(unsigned int version, sudo_conv_t conversation,
     if (argc == 0)
 	debug_return_bool(true);
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     memset(&details, 0, sizeof(details));
 
     bindtextdomain("sudoers", LOCALEDIR);
@@ -674,19 +672,15 @@ done:
 	sudo_gr_delref(details.runas_gr);
     sudo_endgrent();
 
-    sudo_debug_set_default_instance(prev_instance);
-
     debug_return_bool(rval);
 }
 
 static void
 sudoers_io_close(int exit_status, int error)
 {
-    int i, prev_instance;
+    int i;
     debug_decl(sudoers_io_close, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     for (i = 0; i < IOFD_MAX; i++) {
 	if (io_log_files[i].fd.v == NULL)
 	    continue;
@@ -697,7 +691,6 @@ sudoers_io_close(int exit_status, int error)
 #endif
 	    fclose(io_log_files[i].fd.f);
     }
-    sudo_debug_set_default_instance(prev_instance);
 
     sudo_debug_exit(__func__, __FILE__, __LINE__, sudo_debug_subsys);
     if (sudoers_debug_instance != SUDO_DEBUG_INSTANCE_INITIALIZER) {
@@ -711,16 +704,11 @@ sudoers_io_close(int exit_status, int error)
 static int
 sudoers_io_version(int verbose)
 {
-    int prev_instance;
     debug_decl(sudoers_io_version, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     sudo_printf(SUDO_CONV_INFO_MSG, "Sudoers I/O plugin version %s\n",
 	PACKAGE_VERSION);
 
-    sudo_debug_set_default_instance(prev_instance);
-
     debug_return_bool(true);
 }
 
@@ -731,11 +719,9 @@ static int
 sudoers_io_log(const char *buf, unsigned int len, int idx)
 {
     struct timeval now, delay;
-    int prev_instance, rval = true;
+    int rval = true;
     debug_decl(sudoers_io_version, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     gettimeofday(&now, NULL);
 
 #ifdef HAVE_ZLIB_H
@@ -764,8 +750,6 @@ sudoers_io_log(const char *buf, unsigned int len, int idx)
     last_time.tv_sec = now.tv_sec;
     last_time.tv_usec = now.tv_usec;
 
-    sudo_debug_set_default_instance(prev_instance);
-
     debug_return_bool(rval);
 }
 

plugins/sudoers/policy.c

@@ -374,7 +374,7 @@ sudoers_policy_deserialize_info(void *v, char **runas_user, char **runas_group)
     user_umask = umask(SUDO_UMASK);
     umask(user_umask);
 
-    /* Setup debugging if indicated. */
+    /* Setup debugging if indicated. (XXX - do earlier) */
     sudoers_debug_register(&debug_files, plugin_path);
 
     /* Dump settings and user info (XXX - plugin args) */
@@ -538,7 +538,6 @@ sudoers_policy_open(unsigned int version, sudo_conv_t conversation,
     char * const user_info[], char * const envp[], char * const args[])
 {
     struct sudoers_policy_open_info info;
-    int prev_instance, rval;
     debug_decl(sudoers_policy_open, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
     sudo_version = version;
@@ -549,26 +548,18 @@ sudoers_policy_open(unsigned int version, sudo_conv_t conversation,
     if (sudo_version < SUDO_API_MKVERSION(1, 2))
 	args = NULL;
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     /* Call the sudoers init function. */
     info.settings = settings;
     info.user_info = user_info;
     info.plugin_args = args;
-    rval = sudoers_policy_init(&info, envp);
+    debug_return_bool(sudoers_policy_init(&info, envp));
-
-    sudo_debug_set_default_instance(prev_instance);
-    debug_return_bool(rval);
 }
 
 static void
 sudoers_policy_close(int exit_status, int error_code)
 {
-    int prev_instance;
     debug_decl(sudoers_policy_close, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     /* We do not currently log the exit status. */
     if (error_code) {
 	errno = error_code;
@@ -598,7 +589,6 @@ sudoers_policy_close(int exit_status, int error_code)
     }
     sudo_efree(user_gids);
     user_gids = NULL;
-    sudo_debug_set_default_instance(prev_instance);
 
     sudo_debug_exit(__func__, __FILE__, __LINE__, sudo_debug_subsys);
     if (sudoers_debug_instance != SUDO_DEBUG_INSTANCE_INITIALIZER) {
@@ -617,18 +607,13 @@ sudoers_policy_close(int exit_status, int error_code)
 static int
 sudoers_policy_init_session(struct passwd *pwd, char **user_env[])
 {
-    int prev_instance, rval;
     debug_decl(sudoers_policy_init_session, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     /* user_env is only specified for API version 1.2 and higher. */
     if (sudo_version < SUDO_API_MKVERSION(1, 2))
 	user_env = NULL;
 
-    rval = sudo_auth_begin_session(pwd, user_env);
+    debug_return_bool(sudo_auth_begin_session(pwd, user_env));
-    sudo_debug_set_default_instance(prev_instance);
-    debug_return_bool(rval);
 }
 
 static int
@@ -636,10 +621,9 @@ sudoers_policy_check(int argc, char * const argv[], char *env_add[],
     char **command_infop[], char **argv_out[], char **user_env_out[])
 {
     struct sudoers_exec_args exec_args;
-    int prev_instance, rval;
+    int rval;
     debug_decl(sudoers_policy_check, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
     if (!ISSET(sudo_mode, MODE_EDIT))
 	SET(sudo_mode, MODE_RUN);
 
@@ -654,37 +638,28 @@ sudoers_policy_check(int argc, char * const argv[], char *env_add[],
 	    !sudo_auth_needs_end_session())
 	    sudoers_policy.close = NULL;
     }
-    sudo_debug_set_default_instance(prev_instance);
     debug_return_bool(rval);
 }
 
 static int
 sudoers_policy_validate(void)
 {
-    int prev_instance, rval;
     debug_decl(sudoers_policy_validate, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
     user_cmnd = "validate";
     SET(sudo_mode, MODE_VALIDATE);
 
-    rval = sudoers_policy_main(0, NULL, I_VERIFYPW, NULL, NULL);
+    debug_return_bool(sudoers_policy_main(0, NULL, I_VERIFYPW, NULL, NULL));
-    sudo_debug_set_default_instance(prev_instance);
-    debug_return_bool(rval);
 }
 
 static void
 sudoers_policy_invalidate(int remove)
 {
-    int prev_instance;
     debug_decl(sudoers_policy_invalidate, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     user_cmnd = "kill";
     remove_timestamp(remove);
     sudoers_cleanup();
-    sudo_debug_set_default_instance(prev_instance);
 
     debug_return;
 }
@@ -693,11 +668,9 @@ static int
 sudoers_policy_list(int argc, char * const argv[], int verbose,
     const char *list_user)
 {
-    int prev_instance, rval = -1;
+    int rval;
     debug_decl(sudoers_policy_list, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     user_cmnd = "list";
     if (argc)
 	SET(sudo_mode, MODE_CHECK);
@@ -709,7 +682,7 @@ sudoers_policy_list(int argc, char * const argv[], int verbose,
 	list_pw = sudo_getpwnam(list_user);
 	if (list_pw == NULL) {
 	    sudo_warnx(U_("unknown user: %s"), list_user);
-	    goto done;
+	    debug_return_bool(-1);
 	}
     }
     rval = sudoers_policy_main(argc, argv, I_LISTPW, NULL, NULL);
@@ -718,19 +691,14 @@ sudoers_policy_list(int argc, char * const argv[], int verbose,
 	list_pw = NULL;
     }
 
-done:
-    sudo_debug_set_default_instance(prev_instance);
     debug_return_bool(rval);
 }
 
 static int
 sudoers_policy_version(int verbose)
 {
-    int prev_instance;
     debug_decl(sudoers_policy_version, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
 
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
-
     sudo_printf(SUDO_CONV_INFO_MSG, _("Sudoers policy plugin version %s\n"),
 	PACKAGE_VERSION);
     sudo_printf(SUDO_CONV_INFO_MSG, _("Sudoers file grammar version %d\n"),
@@ -753,18 +721,17 @@ sudoers_policy_version(int verbose)
 	    sudo_printf(SUDO_CONV_INFO_MSG, "\n");
 	}
     }
-    sudo_debug_set_default_instance(prev_instance);
     debug_return_bool(true);
 }
 
+/*
+ * Register environment function hooks.
+ * Note that we have not registered sudoers with the debug subsystem yet.
+ */
 static void
 sudoers_policy_register_hooks(int version, int (*register_hook)(struct sudo_hook *hook))
 {
     struct sudo_hook hook;
-    int prev_instance;
-    debug_decl(sudoers_policy_register_hooks, SUDOERS_DEBUG_PLUGIN, sudoers_debug_instance)
-
-    prev_instance = sudo_debug_set_default_instance(sudoers_debug_instance);
 
     memset(&hook, 0, sizeof(hook));
     hook.hook_version = SUDO_HOOK_VERSION;
@@ -784,8 +751,6 @@ sudoers_policy_register_hooks(int version, int (*register_hook)(struct sudo_hook
     hook.hook_type = SUDO_HOOK_PUTENV;
     hook.hook_fn = sudoers_hook_putenv;
     register_hook(&hook);
-
-    sudo_debug_set_default_instance(prev_instance);
 }
 
 __dso_public struct policy_plugin sudoers_policy = {

src/exec_pty.c

@@ -218,7 +218,10 @@ log_ttyin(const char *buf, unsigned int n, struct io_buffer *iob)
     sigprocmask(SIG_BLOCK, &ttyblock, &omask);
     TAILQ_FOREACH(plugin, &io_plugins, entries) {
 	if (plugin->u.io->log_ttyin) {
-	    int rc = plugin->u.io->log_ttyin(buf, n);
+	    int rc;
+
+	    sudo_debug_set_default_instance(plugin->debug_instance);
+	    rc = plugin->u.io->log_ttyin(buf, n);
 	    if (rc <= 0) {
 		if (rc < 0) {
 		    /* Error: disable plugin's I/O function. */
@@ -229,6 +232,7 @@ log_ttyin(const char *buf, unsigned int n, struct io_buffer *iob)
 	    }
 	}
     }
+    sudo_debug_set_default_instance(sudo_debug_instance);
     sigprocmask(SIG_SETMASK, &omask, NULL);
 
     debug_return_bool(rval);
@@ -246,7 +250,10 @@ log_stdin(const char *buf, unsigned int n, struct io_buffer *iob)
     sigprocmask(SIG_BLOCK, &ttyblock, &omask);
     TAILQ_FOREACH(plugin, &io_plugins, entries) {
 	if (plugin->u.io->log_stdin) {
-	    int rc = plugin->u.io->log_stdin(buf, n);
+	    int rc;
+
+	    sudo_debug_set_default_instance(plugin->debug_instance);
+	    rc = plugin->u.io->log_stdin(buf, n);
 	    if (rc <= 0) {
 		if (rc < 0) {
 		    /* Error: disable plugin's I/O function. */
@@ -257,6 +264,7 @@ log_stdin(const char *buf, unsigned int n, struct io_buffer *iob)
 	    }
 	}
     }
+    sudo_debug_set_default_instance(sudo_debug_instance);
     sigprocmask(SIG_SETMASK, &omask, NULL);
 
     debug_return_bool(rval);
@@ -274,7 +282,10 @@ log_ttyout(const char *buf, unsigned int n, struct io_buffer *iob)
     sigprocmask(SIG_BLOCK, &ttyblock, &omask);
     TAILQ_FOREACH(plugin, &io_plugins, entries) {
 	if (plugin->u.io->log_ttyout) {
-	    int rc = plugin->u.io->log_ttyout(buf, n);
+	    int rc;
+
+	    sudo_debug_set_default_instance(plugin->debug_instance);
+	    rc = plugin->u.io->log_ttyout(buf, n);
 	    if (rc <= 0) {
 		if (rc < 0) {
 		    /* Error: disable plugin's I/O function. */
@@ -285,6 +296,7 @@ log_ttyout(const char *buf, unsigned int n, struct io_buffer *iob)
 	    }
 	}
     }
+    sudo_debug_set_default_instance(sudo_debug_instance);
     if (!rval) {
 	/*
 	 * I/O plugin rejected the output, delete the write event
@@ -314,7 +326,10 @@ log_stdout(const char *buf, unsigned int n, struct io_buffer *iob)
     sigprocmask(SIG_BLOCK, &ttyblock, &omask);
     TAILQ_FOREACH(plugin, &io_plugins, entries) {
 	if (plugin->u.io->log_stdout) {
-	    int rc = plugin->u.io->log_stdout(buf, n);
+	    int rc;
+
+	    sudo_debug_set_default_instance(plugin->debug_instance);
+	    rc = plugin->u.io->log_stdout(buf, n);
 	    if (rc <= 0) {
 		if (rc < 0) {
 		    /* Error: disable plugin's I/O function. */
@@ -325,6 +340,7 @@ log_stdout(const char *buf, unsigned int n, struct io_buffer *iob)
 	    }
 	}
     }
+    sudo_debug_set_default_instance(sudo_debug_instance);
     if (!rval) {
 	/*
 	 * I/O plugin rejected the output, delete the write event
@@ -354,7 +370,10 @@ log_stderr(const char *buf, unsigned int n, struct io_buffer *iob)
     sigprocmask(SIG_BLOCK, &ttyblock, &omask);
     TAILQ_FOREACH(plugin, &io_plugins, entries) {
 	if (plugin->u.io->log_stderr) {
-	    int rc = plugin->u.io->log_stderr(buf, n);
+	    int rc;
+
+	    sudo_debug_set_default_instance(plugin->debug_instance);
+	    rc = plugin->u.io->log_stderr(buf, n);
 	    if (rc <= 0) {
 		if (rc < 0) {
 		    /* Error: disable plugin's I/O function. */
@@ -365,6 +384,7 @@ log_stderr(const char *buf, unsigned int n, struct io_buffer *iob)
 	    }
 	}
     }
+    sudo_debug_set_default_instance(sudo_debug_instance);
     if (!rval) {
 	/*
 	 * I/O plugin rejected the output, delete the write event

src/load_plugins.c

@@ -238,6 +238,7 @@ sudo_load_plugin(struct plugin_container *policy_plugin,
 	    policy_plugin->path = sudo_estrdup(path);
 	    policy_plugin->name = info->symbol_name;
 	    policy_plugin->options = info->options;
+	    policy_plugin->debug_instance = SUDO_DEBUG_INSTANCE_INITIALIZER;
 	    policy_plugin->u.generic = plugin;
 	    TAILQ_INIT(&policy_plugin->debug_files);
 	    TAILQ_SWAP(&policy_plugin->debug_files, &info->debug_files,
@@ -260,6 +261,7 @@ sudo_load_plugin(struct plugin_container *policy_plugin,
 	    container->path = sudo_estrdup(path);
 	    container->name = info->symbol_name;
 	    container->options = info->options;
+	    container->debug_instance = SUDO_DEBUG_INSTANCE_INITIALIZER;
 	    container->u.generic = plugin;
 	    TAILQ_INIT(&container->debug_files);
 	    TAILQ_SWAP(&container->debug_files, &info->debug_files,
@@ -329,6 +331,7 @@ sudo_load_plugins(struct plugin_container *policy_plugin,
     }
 
     /* Install hooks (XXX - later). */
+    sudo_debug_set_default_instance(SUDO_DEBUG_INSTANCE_INITIALIZER);
     if (policy_plugin->u.policy->version >= SUDO_API_MKVERSION(1, 2)) {
 	if (policy_plugin->u.policy->register_hooks != NULL)
 	    policy_plugin->u.policy->register_hooks(SUDO_HOOK_VERSION, register_hook);
@@ -339,6 +342,7 @@ sudo_load_plugins(struct plugin_container *policy_plugin,
 		container->u.io->register_hooks(SUDO_HOOK_VERSION, register_hook);
 	}
     }
+    sudo_debug_set_default_instance(sudo_debug_instance);
 
 done:
     debug_return_bool(rval);

src/sudo.c

@@ -1145,6 +1145,7 @@ policy_open(struct plugin_container *plugin, struct sudo_settings *settings,
     /*
      * Backwards compatibility for older API versions
      */
+    sudo_debug_set_default_instance(SUDO_DEBUG_INSTANCE_INITIALIZER);
     switch (plugin->u.generic->version) {
     case SUDO_API_MKVERSION(1, 0):
     case SUDO_API_MKVERSION(1, 1):
@@ -1158,6 +1159,10 @@ policy_open(struct plugin_container *plugin, struct sudo_settings *settings,
 	    plugin->options);
     }
 
+    /* Stash plugin debug instance ID if set in open() function. */
+    plugin->debug_instance = sudo_debug_get_default_instance();
+    sudo_debug_set_default_instance(sudo_debug_instance);
+
     debug_return_bool(rval);
 }
 
@@ -1166,7 +1171,9 @@ policy_close(struct plugin_container *plugin, int exit_status, int error_code)
 {
     debug_decl(policy_close, SUDO_DEBUG_PCOMM, sudo_debug_instance)
     if (plugin->u.policy->close != NULL) {
+	sudo_debug_set_default_instance(plugin->debug_instance);
 	plugin->u.policy->close(exit_status, error_code);
+	sudo_debug_set_default_instance(sudo_debug_instance);
     } else if (error_code) {
 	errno = error_code;
 	sudo_warn(U_("unable to execute %s"), command_details.command);
@@ -1177,10 +1184,15 @@ policy_close(struct plugin_container *plugin, int exit_status, int error_code)
 static int
 policy_show_version(struct plugin_container *plugin, int verbose)
 {
+    int rval;
     debug_decl(policy_show_version, SUDO_DEBUG_PCOMM, sudo_debug_instance)
+
     if (plugin->u.policy->show_version == NULL)
 	debug_return_bool(true);
-    debug_return_bool(plugin->u.policy->show_version(verbose));
+    sudo_debug_set_default_instance(plugin->debug_instance);
+    rval = plugin->u.policy->show_version(verbose);
+    sudo_debug_set_default_instance(sudo_debug_instance);
+    debug_return_bool(rval);
 }
 
 static int
@@ -1188,38 +1200,53 @@ policy_check(struct plugin_container *plugin, int argc, char * const argv[],
     char *env_add[], char **command_info[], char **argv_out[],
     char **user_env_out[])
 {
+    int rval;
     debug_decl(policy_check, SUDO_DEBUG_PCOMM, sudo_debug_instance)
+
     if (plugin->u.policy->check_policy == NULL) {
 	sudo_fatalx(U_("policy plugin %s is missing the `check_policy' method"),
 	    plugin->name);
     }
-    debug_return_bool(plugin->u.policy->check_policy(argc, argv, env_add,
+    sudo_debug_set_default_instance(plugin->debug_instance);
-	command_info, argv_out, user_env_out));
+    rval = plugin->u.policy->check_policy(argc, argv, env_add, command_info,
+	argv_out, user_env_out);
+    sudo_debug_set_default_instance(sudo_debug_instance);
+    debug_return_bool(rval);
 }
 
 static int
 policy_list(struct plugin_container *plugin, int argc, char * const argv[],
     int verbose, const char *list_user)
 {
+    int rval;
     debug_decl(policy_list, SUDO_DEBUG_PCOMM, sudo_debug_instance)
+
     if (plugin->u.policy->list == NULL) {
 	sudo_warnx(U_("policy plugin %s does not support listing privileges"),
 	    plugin->name);
 	debug_return_bool(false);
     }
-    debug_return_bool(plugin->u.policy->list(argc, argv, verbose, list_user));
+    sudo_debug_set_default_instance(plugin->debug_instance);
+    rval = plugin->u.policy->list(argc, argv, verbose, list_user);
+    sudo_debug_set_default_instance(sudo_debug_instance);
+    debug_return_bool(rval);
 }
 
 static int
 policy_validate(struct plugin_container *plugin)
 {
+    int rval;
     debug_decl(policy_validate, SUDO_DEBUG_PCOMM, sudo_debug_instance)
+
     if (plugin->u.policy->validate == NULL) {
 	sudo_warnx(U_("policy plugin %s does not support the -v option"),
 	    plugin->name);
 	debug_return_bool(false);
     }
-    debug_return_bool(plugin->u.policy->validate());
+    sudo_debug_set_default_instance(plugin->debug_instance);
+    rval = plugin->u.policy->validate();
+    sudo_debug_set_default_instance(sudo_debug_instance);
+    debug_return_bool(rval);
 }
 
 static void
@@ -1230,7 +1257,9 @@ policy_invalidate(struct plugin_container *plugin, int remove)
 	sudo_fatalx(U_("policy plugin %s does not support the -k/-K options"),
 	    plugin->name);
     }
+    sudo_debug_set_default_instance(plugin->debug_instance);
     plugin->u.policy->invalidate(remove);
+    sudo_debug_set_default_instance(sudo_debug_instance);
     debug_return;
 }
 
@@ -1244,6 +1273,7 @@ policy_init_session(struct command_details *details)
 	/*
 	 * Backwards compatibility for older API versions
 	 */
+	sudo_debug_set_default_instance(policy_plugin.debug_instance);
 	switch (policy_plugin.u.generic->version) {
 	case SUDO_API_MKVERSION(1, 0):
 	case SUDO_API_MKVERSION(1, 1):
@@ -1253,6 +1283,7 @@ policy_init_session(struct command_details *details)
 	    rval = policy_plugin.u.policy->init_session(details->pw,
 		&details->envp);
 	}
+	sudo_debug_set_default_instance(sudo_debug_instance);
     }
     debug_return_bool(rval);
 }
@@ -1274,6 +1305,7 @@ iolog_open(struct plugin_container *plugin, struct sudo_settings *settings,
     /*
      * Backwards compatibility for older API versions
      */
+    sudo_debug_set_default_instance(plugin->debug_instance);
     switch (plugin->u.generic->version) {
     case SUDO_API_MKVERSION(1, 0):
 	rval = plugin->u.io_1_0->open(plugin->u.io_1_0->version,
@@ -1290,6 +1322,7 @@ iolog_open(struct plugin_container *plugin, struct sudo_settings *settings,
 	    sudo_conversation_printf, plugin_settings, user_info, command_info,
 	    argc, argv, user_env, plugin->options);
     }
+    sudo_debug_set_default_instance(sudo_debug_instance);
     debug_return_bool(rval);
 }
 
@@ -1297,18 +1330,28 @@ static void
 iolog_close(struct plugin_container *plugin, int exit_status, int error_code)
 {
     debug_decl(iolog_close, SUDO_DEBUG_PCOMM, sudo_debug_instance)
-    if (plugin->u.io->close != NULL)
+
+    if (plugin->u.io->close != NULL) {
+	sudo_debug_set_default_instance(plugin->debug_instance);
 	plugin->u.io->close(exit_status, error_code);
+	sudo_debug_set_default_instance(sudo_debug_instance);
+    }
     debug_return;
 }
 
 static int
 iolog_show_version(struct plugin_container *plugin, int verbose)
 {
+    int rval;
     debug_decl(iolog_show_version, SUDO_DEBUG_PCOMM, sudo_debug_instance)
+
     if (plugin->u.io->show_version == NULL)
 	debug_return_bool(true);
-    debug_return_bool(plugin->u.io->show_version(verbose));
+
+    sudo_debug_set_default_instance(plugin->debug_instance);
+    rval = plugin->u.io->show_version(verbose);
+    sudo_debug_set_default_instance(sudo_debug_instance);
+    debug_return_bool(rval);
 }
 
 /*
@@ -1322,9 +1365,12 @@ iolog_unlink(struct plugin_container *plugin)
 
     /* Deregister hooks, if any. */
     if (plugin->u.io->version >= SUDO_API_MKVERSION(1, 2)) {
-	if (plugin->u.io->deregister_hooks != NULL)
+	if (plugin->u.io->deregister_hooks != NULL) {
+	    sudo_debug_set_default_instance(plugin->debug_instance);
 	    plugin->u.io->deregister_hooks(SUDO_HOOK_VERSION,
 		deregister_hook);
+	    sudo_debug_set_default_instance(sudo_debug_instance);
+	}
     }
     /* Remove from io_plugins list and free. */
     TAILQ_REMOVE(&io_plugins, plugin, entries);

src/sudo_plugin_int.h

@@ -87,6 +87,7 @@ struct plugin_container {
     const char *path;
     char * const *options;
     void *handle;
+    int debug_instance;
     union {
 	struct generic_plugin *generic;
 	struct policy_plugin *policy;