Commit e80eb1dc authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

bpfilter: Take advantage of the facilities of struct pid 

Instead of relying on the exit_umh cleanup callback use the fact a
struct pid can be tested to see if a process still exists, and that
struct pid has a wait queue that notifies when the process dies.

v1: https://lkml.kernel.org/r/87h7uydlu9.fsf_-_@x220.int.ebiederm.org
v2: https://lkml.kernel.org/r/874kqt4owu.fsf_-_@x220.int.ebiederm.org
Link: https://lkml.kernel.org/r/20200702164140.4468-14-ebiederm@xmission.com


Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Tested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 38fd525a

include/linux/bpfilter.h

+2 −1
Original line number Diff line number Diff line
@@ -10,6 +10,8 @@ int bpfilter_ip_set_sockopt(struct sock *sk, int optname, char __user *optval, 
			    unsigned int optlen);

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 */
@@ -18,7 +20,6 @@ struct bpfilter_umh_ops { 
		       char __user *optval,

		       unsigned int optlen, bool is_set);

	int (*start)(void);

	bool stop;

};

extern struct bpfilter_umh_ops bpfilter_ops;

#endif

net/bpfilter/bpfilter_kern.c

+5 −10
Original line number Diff line number Diff line
@@ -18,10 +18,11 @@ static void shutdown_umh(void) 
	struct umd_info *info = &bpfilter_ops.info;

	struct pid *tgid = info->tgid;



	if (bpfilter_ops.stop)

		return;



	if (tgid) {

		kill_pid(tgid, SIGKILL, 1);

		wait_event(tgid->wait_pidfd, thread_group_exited(tgid));

		bpfilter_umh_cleanup(info);

	}

}



static void __stop_umh(void)
@@ -77,7 +78,6 @@ static int start_umh(void) 
	err = fork_usermode_driver(&bpfilter_ops.info);

	if (err)

		return err;

	bpfilter_ops.stop = false;

	pr_info("Loaded bpfilter_umh pid %d\n", pid_nr(bpfilter_ops.info.tgid));



	/* health check that usermode process started correctly */
@@ -100,16 +100,11 @@ static int __init load_umh(void) 
		return err;



	mutex_lock(&bpfilter_ops.lock);

	if (!bpfilter_ops.stop) {

		err = -EFAULT;

		goto out;

	}

	err = start_umh();

	if (!err && IS_ENABLED(CONFIG_INET)) {

		bpfilter_ops.sockopt = &__bpfilter_process_sockopt;

		bpfilter_ops.start = &start_umh;

	}

out:

	mutex_unlock(&bpfilter_ops.lock);

	if (err)

		umd_unload_blob(&bpfilter_ops.info);

net/ipv4/bpfilter/sockopt.c

+8 −7
Original line number Diff line number Diff line
@@ -12,16 +12,14 @@ 
struct bpfilter_umh_ops bpfilter_ops;

EXPORT_SYMBOL_GPL(bpfilter_ops);



static void bpfilter_umh_cleanup(struct umd_info *info)

void bpfilter_umh_cleanup(struct umd_info *info)

{

	mutex_lock(&bpfilter_ops.lock);

	bpfilter_ops.stop = true;

	fput(info->pipe_to_umh);

	fput(info->pipe_from_umh);

	put_pid(info->tgid);

	info->tgid = NULL;

	mutex_unlock(&bpfilter_ops.lock);

}

EXPORT_SYMBOL_GPL(bpfilter_umh_cleanup);



static int bpfilter_mbox_request(struct sock *sk, int optname,

				 char __user *optval,
@@ -39,7 +37,11 @@ static int bpfilter_mbox_request(struct sock *sk, int optname, 
			goto out;

		}

	}

	if (bpfilter_ops.stop) {

	if (bpfilter_ops.info.tgid &&

	    thread_group_exited(bpfilter_ops.info.tgid))

		bpfilter_umh_cleanup(&bpfilter_ops.info);



	if (!bpfilter_ops.info.tgid) {

		err = bpfilter_ops.start();

		if (err)

			goto out;
@@ -70,9 +72,8 @@ int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval, 
static int __init bpfilter_sockopt_init(void)

{

	mutex_init(&bpfilter_ops.lock);

	bpfilter_ops.stop = true;

	bpfilter_ops.info.tgid = NULL;

	bpfilter_ops.info.driver_name = "bpfilter_umh";

	bpfilter_ops.info.cleanup = &bpfilter_umh_cleanup;



	return 0;

}

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