[PATCH 3/5] bpfilter: Port to user mode driver management API

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>

Move bpfilter_process_sockopt() to sockopt.c, and call umd_mgmt_send_recv()
instead of umd_send_recv(), so that it has the original capability of
bpfilter_mbox_request() to request the loading of the kernel module
containing the user mode driver.

Move also the connection test originally in start_umh() in bpfilter.c, to
sockopt.c. Create the new function bpfilter_post_start_umh() with the moved
code.

Directly call bpfilter_process_sockopt() from bpfilter_ip_set_sockopt() and
bpfilter_ip_get_sockopt(), which now it is equivalent to
bpfilter_mbox_request().

Remove the struct bpfilter_umh_ops definition, and declare the global
variable bpfilter_ops as a umd_mgmt structure.

Set kmod to 'bpfilter', kmod_loaded to false and the new function
bpfilter_post_start_umh() as the post_start method for bpfilter_ops.

Replace load_umh() and fini_umh() in bpfilter.c respectively with
umd_mgmt_load() and umd_mgmt_unload().

Finally, remove the remaining functions, as their job is done by the user
mode driver management.

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
 include/linux/bpfilter.h     | 12 +----
 net/bpfilter/bpfilter_kern.c | 98 ++----------------------------------
 net/ipv4/bpfilter/sockopt.c  | 67 ++++++++++++++----------
 3 files changed, 45 insertions(+), 132 deletions(-)

diff --git a/include/linux/bpfilter.h b/include/linux/bpfilter.h
index 2ae3c8e1d83..655e6ec6e9d 100644
--- a/include/linux/bpfilter.h
+++ b/include/linux/bpfilter.h
@@ -3,7 +3,7 @@
 #define _LINUX_BPFILTER_H
 
 #include <uapi/linux/bpfilter.h>
-#include <linux/usermode_driver.h>
+#include <linux/usermode_driver_mgmt.h>
 #include <linux/sockptr.h>
 
 struct sock;
@@ -13,13 +13,5 @@ int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval,
 			    int __user *optlen);
 void bpfilter_umh_cleanup(struct umd_info *info);
 
-struct bpfilter_umh_ops {
-	struct umd_info info;
-	/* since ip_getsockopt() can run in parallel, serialize access to umh */
-	struct mutex lock;
-	int (*sockopt)(struct sock *sk, int optname, sockptr_t optval,
-		       unsigned int optlen, bool is_set);
-	int (*start)(void);
-};
-extern struct bpfilter_umh_ops bpfilter_ops;
+extern struct umd_mgmt bpfilter_ops;
 #endif
diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 17d4df5f8fe..f2137d889c9 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -1,113 +1,21 @@
 // SPDX-License-Identifier: GPL-2.0
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#include <linux/init.h>
 #include <linux/module.h>
-#include <linux/umh.h>
 #include <linux/bpfilter.h>
-#include <linux/sched.h>
-#include <linux/sched/signal.h>
-#include <linux/fs.h>
-#include <linux/file.h>
 #include "msgfmt.h"
 
 extern char bpfilter_umh_start;
 extern char bpfilter_umh_end;
 
-static void shutdown_umh(void)
-{
-	struct umd_info *info = &bpfilter_ops.info;
-	struct pid *tgid = info->tgid;
-
-	if (tgid) {
-		kill_pid(tgid, SIGKILL, 1);
-		wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
-		bpfilter_umh_cleanup(info);
-	}
-}
-
-static int bpfilter_process_sockopt(struct sock *sk, int optname,
-				    sockptr_t optval, unsigned int optlen,
-				    bool is_set)
-{
-	struct mbox_request req = {
-		.is_set		= is_set,
-		.pid		= current->pid,
-		.cmd		= optname,
-		.addr		= (uintptr_t)optval.user,
-		.len		= optlen,
-	};
-	struct mbox_reply reply;
-	int err;
-
-	if (sockptr_is_kernel(optval)) {
-		pr_err("kernel access not supported\n");
-		return -EFAULT;
-	}
-	err = umd_send_recv(&bpfilter_ops.info, &req, sizeof(req), &reply,
-			    sizeof(reply));
-	if (err) {
-		shutdown_umh();
-		return err;
-	}
-
-	return reply.status;
-}
-
-static int start_umh(void)
-{
-	struct mbox_request req = { .pid = current->pid };
-	struct mbox_reply reply;
-	int err;
-
-	/* fork usermode process */
-	err = fork_usermode_driver(&bpfilter_ops.info);
-	if (err)
-		return err;
-	pr_info("Loaded bpfilter_umh pid %d\n", pid_nr(bpfilter_ops.info.tgid));
-
-	/* health check that usermode process started correctly */
-	if (umd_send_recv(&bpfilter_ops.info, &req, sizeof(req), &reply,
-			  sizeof(reply)) != 0 || reply.status != 0) {
-		shutdown_umh();
-		return -EFAULT;
-	}
-
-	return 0;
-}
-
 static int __init load_umh(void)
 {
-	int err;
-
-	err = umd_load_blob(&bpfilter_ops.info,
-			    &bpfilter_umh_start,
-			    &bpfilter_umh_end - &bpfilter_umh_start);
-	if (err)
-		return err;
-
-	mutex_lock(&bpfilter_ops.lock);
-	err = start_umh();
-	if (!err && IS_ENABLED(CONFIG_INET)) {
-		bpfilter_ops.sockopt = &bpfilter_process_sockopt;
-		bpfilter_ops.start = &start_umh;
-	}
-	mutex_unlock(&bpfilter_ops.lock);
-	if (err)
-		umd_unload_blob(&bpfilter_ops.info);
-	return err;
+	return umd_mgmt_load(&bpfilter_ops, &bpfilter_umh_start,
+			     &bpfilter_umh_end);
 }
 
 static void __exit fini_umh(void)
 {
-	mutex_lock(&bpfilter_ops.lock);
-	if (IS_ENABLED(CONFIG_INET)) {
-		shutdown_umh();
-		bpfilter_ops.start = NULL;
-		bpfilter_ops.sockopt = NULL;
-	}
-	mutex_unlock(&bpfilter_ops.lock);
-
-	umd_unload_blob(&bpfilter_ops.info);
+	umd_mgmt_unload(&bpfilter_ops);
 }
 module_init(load_umh);
 module_exit(fini_umh);
diff --git a/net/ipv4/bpfilter/sockopt.c b/net/ipv4/bpfilter/sockopt.c
index 1b34cb9a770..491f5042612 100644
--- a/net/ipv4/bpfilter/sockopt.c
+++ b/net/ipv4/bpfilter/sockopt.c
@@ -8,8 +8,9 @@
 #include <linux/kmod.h>
 #include <linux/fs.h>
 #include <linux/file.h>
+#include "../../bpfilter/msgfmt.h"
 
-struct bpfilter_umh_ops bpfilter_ops;
+struct umd_mgmt bpfilter_ops;
 EXPORT_SYMBOL_GPL(bpfilter_ops);
 
 void bpfilter_umh_cleanup(struct umd_info *info)
@@ -21,40 +22,49 @@ void bpfilter_umh_cleanup(struct umd_info *info)
 }
 EXPORT_SYMBOL_GPL(bpfilter_umh_cleanup);
 
-static int bpfilter_mbox_request(struct sock *sk, int optname, sockptr_t optval,
-				 unsigned int optlen, bool is_set)
+static int bpfilter_process_sockopt(struct sock *sk, int optname,
+				    sockptr_t optval, unsigned int optlen,
+				    bool is_set)
 {
+	struct mbox_request req = {
+		.is_set		= is_set,
+		.pid		= current->pid,
+		.cmd		= optname,
+		.addr		= (uintptr_t)optval.user,
+		.len		= optlen,
+	};
+	struct mbox_reply reply;
 	int err;
-	mutex_lock(&bpfilter_ops.lock);
-	if (!bpfilter_ops.sockopt) {
-		mutex_unlock(&bpfilter_ops.lock);
-		request_module("bpfilter");
-		mutex_lock(&bpfilter_ops.lock);
 
-		if (!bpfilter_ops.sockopt) {
-			err = -ENOPROTOOPT;
-			goto out;
-		}
+	if (sockptr_is_kernel(optval)) {
+		pr_err("kernel access not supported\n");
+		return -EFAULT;
 	}
-	if (bpfilter_ops.info.tgid &&
-	    thread_group_exited(bpfilter_ops.info.tgid))
-		bpfilter_umh_cleanup(&bpfilter_ops.info);
+	err = umd_mgmt_send_recv(&bpfilter_ops, &req, sizeof(req), &reply,
+				 sizeof(reply));
+	if (err)
+		return err;
 
-	if (!bpfilter_ops.info.tgid) {
-		err = bpfilter_ops.start();
-		if (err)
-			goto out;
-	}
-	err = bpfilter_ops.sockopt(sk, optname, optval, optlen, is_set);
-out:
-	mutex_unlock(&bpfilter_ops.lock);
-	return err;
+	return reply.status;
+}
+
+static int bpfilter_post_start_umh(struct umd_mgmt *mgmt)
+{
+	struct mbox_request req = { .pid = current->pid };
+	struct mbox_reply reply;
+
+	/* health check that usermode process started correctly */
+	if (umd_send_recv(&bpfilter_ops.info, &req, sizeof(req), &reply,
+			  sizeof(reply)) != 0 || reply.status != 0)
+		return -EFAULT;
+
+	return 0;
 }
 
 int bpfilter_ip_set_sockopt(struct sock *sk, int optname, sockptr_t optval,
 			    unsigned int optlen)
 {
-	return bpfilter_mbox_request(sk, optname, optval, optlen, true);
+	return bpfilter_process_sockopt(sk, optname, optval, optlen, true);
 }
 
 int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval,
@@ -65,8 +75,8 @@ int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval,
 	if (get_user(len, optlen))
 		return -EFAULT;
 
-	return bpfilter_mbox_request(sk, optname, USER_SOCKPTR(optval), len,
-				     false);
+	return bpfilter_process_sockopt(sk, optname, USER_SOCKPTR(optval), len,
+					false);
 }
 
 static int __init bpfilter_sockopt_init(void)
@@ -74,6 +84,9 @@ static int __init bpfilter_sockopt_init(void)
 	mutex_init(&bpfilter_ops.lock);
 	bpfilter_ops.info.tgid = NULL;
 	bpfilter_ops.info.driver_name = "bpfilter_umh";
+	bpfilter_ops.post_start = bpfilter_post_start_umh;
+	bpfilter_ops.kmod = "bpfilter";
+	bpfilter_ops.kmod_loaded = false;
 
 	return 0;
 }
-- 
2.25.1