net: bpfilter: restart bpfilter_umh when error occurred

The bpfilter_umh will be stopped via __stop_umh() when the bpfilter
error occurred.
The bpfilter_umh() couldn't start again because there is no restart
routine.

The section of the bpfilter_umh_{start/end} is no longer .init.rodata
because these area should be reused in the restart routine. hence
the section name is changed to .bpfilter_umh.

The bpfilter_ops->start() is restart callback. it will be called when
bpfilter_umh is stopped.
The stop bit means bpfilter_umh is stopped. this bit is set by both
start and stop routine.

Before this patch,
Test commands:
   $ iptables -vnL
   $ kill -9 <pid of bpfilter_umh>
   $ iptables -vnL
   [  480.045136] bpfilter: write fail -32
   $ iptables -vnL

All iptables commands will fail.

After this patch,
Test commands:
   $ iptables -vnL
   $ kill -9 <pid of bpfilter_umh>
   $ iptables -vnL
   $ iptables -vnL

Now, all iptables commands will work.

Fixes: 6507af9e4e23 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/bpfilter.h b/include/linux/bpfilter.h
index 70ffeed280e9dc02d0ea1ef3766a41f937b373f6..8ebcbdd70bdc55f8c9b93aa643d06145f0a453ed 100644 (file)
--- a/include/linux/bpfilter.h
+++ b/include/linux/bpfilter.h
@@ -15,6 +15,8 @@ struct bpfilter_umh_ops {
        int (*sockopt)(struct sock *sk, int optname,
                       char __user *optval,
                       unsigned int optlen, bool is_set);
+       int (*start)(void);
+       bool stop;
 };
 extern struct bpfilter_umh_ops bpfilter_ops;
 #endif

diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index a68940b74c0154a76f28c6d99aeaf29ad68f0fe9..c0fcde910a7ad75277765aaf7d7476cdc7dc861e 100644 (file)
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -16,13 +16,14 @@ extern char bpfilter_umh_end;
 /* since ip_getsockopt() can run in parallel, serialize access to umh */
 static DEFINE_MUTEX(bpfilter_lock);
 
-static void shutdown_umh(struct umh_info *info)
+static void shutdown_umh(void)
 {
        struct task_struct *tsk;
 
-       if (!info->pid)
+       if (bpfilter_ops.stop)
                return;
-       tsk = get_pid_task(find_vpid(info->pid), PIDTYPE_PID);
+
+       tsk = get_pid_task(find_vpid(bpfilter_ops.info.pid), PIDTYPE_PID);
        if (tsk) {
                force_sig(SIGKILL, tsk);
                put_task_struct(tsk);
@@ -31,10 +32,8 @@ static void shutdown_umh(struct umh_info *info)
 
 static void __stop_umh(void)
 {
-       if (IS_ENABLED(CONFIG_INET)) {
-               bpfilter_ops.sockopt = NULL;
-               shutdown_umh(&bpfilter_ops.info);
-       }
+       if (IS_ENABLED(CONFIG_INET))
+               shutdown_umh();
 }
 
 static void stop_umh(void)
@@ -85,7 +84,7 @@ out:
        return ret;
 }
 
-static int __init load_umh(void)
+static int start_umh(void)
 {
        int err;
 
@@ -95,6 +94,7 @@ static int __init load_umh(void)
                                 &bpfilter_ops.info);
        if (err)
                return err;
+       bpfilter_ops.stop = false;
        pr_info("Loaded bpfilter_umh pid %d\n", bpfilter_ops.info.pid);
 
        /* health check that usermode process started correctly */
@@ -102,14 +102,31 @@ static int __init load_umh(void)
                stop_umh();
                return -EFAULT;
        }
-       if (IS_ENABLED(CONFIG_INET))
-               bpfilter_ops.sockopt = &__bpfilter_process_sockopt;
 
        return 0;
 }
 
+static int __init load_umh(void)
+{
+       int err;
+
+       if (!bpfilter_ops.stop)
+               return -EFAULT;
+       err = start_umh();
+       if (!err && IS_ENABLED(CONFIG_INET)) {
+               bpfilter_ops.sockopt = &__bpfilter_process_sockopt;
+               bpfilter_ops.start = &start_umh;
+       }
+
+       return err;
+}
+
 static void __exit fini_umh(void)
 {
+       if (IS_ENABLED(CONFIG_INET)) {
+               bpfilter_ops.start = NULL;
+               bpfilter_ops.sockopt = NULL;
+       }
        stop_umh();
 }
 module_init(load_umh);

diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S
index 40311d10d2f270adbb7a51cfc3bad0c2834ca438..7f1c521dcc2f75fadbc9c6241c2c60c7a1d6b24b 100644 (file)
--- a/net/bpfilter/bpfilter_umh_blob.S
+++ b/net/bpfilter/bpfilter_umh_blob.S
@@ -1,5 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-       .section .init.rodata, "a"
+       .section .bpfilter_umh, "a"
        .global bpfilter_umh_start
 bpfilter_umh_start:
        .incbin "net/bpfilter/bpfilter_umh"

diff --git a/net/ipv4/bpfilter/sockopt.c b/net/ipv4/bpfilter/sockopt.c
index c326cfbc0f62198afae382f71f0b4a480e97aa84..de84ede4e76537ec84fb1520423f22587aed391a 100644 (file)
--- a/net/ipv4/bpfilter/sockopt.c
+++ b/net/ipv4/bpfilter/sockopt.c
@@ -14,6 +14,7 @@ EXPORT_SYMBOL_GPL(bpfilter_ops);
 
 static void bpfilter_umh_cleanup(struct umh_info *info)
 {
+       bpfilter_ops.stop = true;
        fput(info->pipe_to_umh);
        fput(info->pipe_from_umh);
        info->pid = 0;
@@ -23,14 +24,21 @@ static int bpfilter_mbox_request(struct sock *sk, int optname,
                                 char __user *optval,
                                 unsigned int optlen, bool is_set)
 {
+       int err;
+
        if (!bpfilter_ops.sockopt) {
-               int err = request_module("bpfilter");
+               err = request_module("bpfilter");
 
                if (err)
                        return err;
                if (!bpfilter_ops.sockopt)
                        return -ECHILD;
        }
+       if (bpfilter_ops.stop) {
+               err = bpfilter_ops.start();
+               if (err)
+                       return err;
+       }
        return bpfilter_ops.sockopt(sk, optname, optval, optlen, is_set);
 }
 
@@ -53,6 +61,7 @@ int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval,
 
 static int __init bpfilter_sockopt_init(void)
 {
+       bpfilter_ops.stop = true;
        bpfilter_ops.info.cmdline = "bpfilter_umh";
        bpfilter_ops.info.cleanup = &bpfilter_umh_cleanup;