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: d2ba09c17a06 ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 1 deletions

diff --git a/net/ipv4/bpfilter/sockopt.c b/net/ipv4/bpfilter/sockopt.c
index c326cfbc0f62..de84ede4e765 100644
--- 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;