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net: bpfilter: restart bpfilter_umh when error occurred

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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: d2ba09c17a ("net: add skeleton of bpfilter kernel module")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Taehee Yoo 2019-01-09 02:24:53 +09:00 committed by David S. Miller
parent 5b4cb650e5
commit 61fbf5933d
4 changed files with 40 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/bpfilter.h
View File

@ -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

37
net/bpfilter/bpfilter_kern.c
View File

@ -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);

2
net/bpfilter/bpfilter_umh_blob.S
View File

@ -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"

11
net/ipv4/bpfilter/sockopt.c
View File

@ -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;