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Date: Tue, 31 Mar 2015 11:14:42 +0800
From: Ian Kent <raven@...maw.net>
To: Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: David Howells <dhowells@...hat.com>,
Oleg Nesterov <onestero@...hat.com>,
Trond Myklebust <trond.myklebust@...marydata.com>,
"J. Bruce Fields" <bfields@...ldses.org>,
Benjamin Coddington <bcodding@...hat.com>,
Al Viro <viro@...IV.linux.org.uk>,
Jeff Layton <jeff.layton@...marydata.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [RFC PATCH 5 1/7] kmod - add workqueue service thread store
From: Ian Kent <ikent@...hat.com>
Persistent use of process information is needed for contained
execution in a namespace other than the root init namespace.
Use a simple random token as a key to create and store thread
information in a hashed list for use by the usermode helper
thread runner.
Signed-off-by: Ian Kent <ikent@...hat.com>
Cc: Benjamin Coddington <bcodding@...hat.com>
Cc: Al Viro <viro@...IV.linux.org.uk>
Cc: J. Bruce Fields <bfields@...ldses.org>
Cc: David Howells <dhowells@...hat.com>
Cc: Trond Myklebust <trond.myklebust@...marydata.com>
Cc: Oleg Nesterov <onestero@...hat.com>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Jeff Layton <jeff.layton@...marydata.com>
---
include/linux/kmod.h | 3 +
kernel/kmod.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 181 insertions(+), 1 deletion(-)
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 0555cc6..fa46722 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -66,6 +66,9 @@ struct subprocess_info {
void *data;
};
+extern int umh_wq_get_token(int token, const char *service);
+extern void umh_wq_put_token(int token);
+
extern int
call_usermodehelper(char *path, char **argv, char **envp, int wait);
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 2777f40..55d20ce 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -40,13 +40,30 @@
#include <linux/ptrace.h>
#include <linux/async.h>
#include <asm/uaccess.h>
+#include <linux/hash.h>
+#include <linux/list.h>
+#include <linux/random.h>
#include <trace/events/module.h>
extern int max_threads;
+#define KHELPER "khelper"
static struct workqueue_struct *khelper_wq;
+#define UMH_WQ_HASH_SHIFT 6
+#define UMH_WQ_HASH_SIZE 1 << UMH_WQ_HASH_SHIFT
+
+struct umh_wq_entry {
+ int token;
+ unsigned int count;
+ struct workqueue_struct *wq;
+ struct hlist_node umh_wq_hlist;
+};
+
+static DEFINE_SPINLOCK(umh_wq_hash_lock);
+static struct hlist_head umh_wq_hash[UMH_WQ_HASH_SIZE];
+
#define CAP_BSET (void *)1
#define CAP_PI (void *)2
@@ -475,6 +492,165 @@ static void helper_unlock(void)
wake_up(&running_helpers_waitq);
}
+static void umh_wq_hash_init(void)
+{
+ int i;
+
+ for (i = 0; i < UMH_WQ_HASH_SIZE; i++)
+ INIT_HLIST_HEAD(&umh_wq_hash[i]);
+}
+
+static struct umh_wq_entry *umh_wq_find_entry(int token)
+{
+ struct umh_wq_entry *this, *entry;
+ struct hlist_head *bucket;
+ unsigned int hash;
+
+ hash = hash_32((unsigned long) token, UMH_WQ_HASH_SHIFT);
+ bucket = &umh_wq_hash[hash];
+
+ entry = ERR_PTR(-ENOENT);
+ if (hlist_empty(bucket))
+ goto out;
+
+ hlist_for_each_entry(this, bucket, umh_wq_hlist) {
+ if (this->token == token) {
+ entry = this;
+ break;
+ }
+ }
+out:
+ return entry;
+}
+
+static struct workqueue_struct *umh_find_wq(int token, unsigned int nowait)
+{
+ struct umh_wq_entry *entry;
+ unsigned long flags;
+
+ if (!token)
+ return khelper_wq;
+
+ if (nowait)
+ spin_lock_irqsave(&umh_wq_hash_lock, flags);
+ else
+ spin_lock(&umh_wq_hash_lock);
+ entry = umh_wq_find_entry(token);
+ if (nowait)
+ spin_unlock_irqrestore(&umh_wq_hash_lock, flags);
+ else
+ spin_unlock(&umh_wq_hash_lock);
+
+ return entry->wq;
+}
+
+/**
+ * umh_wq_get_token - create service thread and return an identifying token
+ * @token: token of an existing service thread or 0 to create a new
+ * service thread.
+ * @name: service name to be appended to "khelper" for identification.
+ *
+ * Returns a token that used with calls to call_usermode_helper_service().
+ * If token corresponds to an existing service thread its reference count
+ * is increased and the token returned. On failure returns a negative errno.
+ */
+int umh_wq_get_token(int token, const char *service)
+{
+ struct workqueue_struct *wq;
+ char *wq_name;
+ int wq_name_len;
+ struct umh_wq_entry *entry;
+ struct hlist_head *bucket;
+ unsigned int hash;
+ unsigned int new_token;
+
+ if (token) {
+ spin_lock(&umh_wq_hash_lock);
+ entry = umh_wq_find_entry(token);
+ if (entry) {
+ entry->count++;
+ spin_unlock(&umh_wq_hash_lock);
+ return token;
+ }
+ spin_unlock(&umh_wq_hash_lock);
+ }
+
+ if (!service)
+ return -EINVAL;
+
+ wq_name_len = sizeof(KHELPER) + strlen(service) + 1;
+ wq_name = kmalloc(wq_name_len, GFP_KERNEL);
+ if (!wq_name)
+ return -ENOMEM;
+ strcpy(wq_name, "KHELPER-");
+ strcat(wq_name, service);
+
+ entry = kzalloc(sizeof(struct umh_wq_entry), GFP_KERNEL);
+ if (!entry) {
+ kfree(wq_name);
+ return -ENOMEM;
+ }
+
+ wq = create_singlethread_workqueue(wq_name);
+ if (IS_ERR(wq)) {
+ kfree(wq_name);
+ kfree(entry);
+ return PTR_ERR(wq);
+ }
+ kfree(wq_name);
+ entry->wq = wq;
+
+ do {
+ new_token = get_random_int();
+ if (!new_token)
+ continue;
+ spin_lock(&umh_wq_hash_lock);
+ entry = umh_wq_find_entry(new_token);
+ if (likely(IS_ERR(entry))) {
+ hash = hash_32(new_token, UMH_WQ_HASH_SHIFT);
+ bucket = &umh_wq_hash[hash];
+ hlist_add_head(&entry->umh_wq_hlist, bucket);
+ entry->token = (long) new_token;
+ spin_unlock(&umh_wq_hash_lock);
+ break;
+ }
+ spin_unlock(&umh_wq_hash_lock);
+ } while (1);
+
+ return (int) new_token;
+}
+EXPORT_SYMBOL(umh_wq_get_token);
+
+/**
+ * umh_ns_put_token - stop a service thread if it's not longer in use
+ * and remove it from the serive thread list
+ * @token: token of a service thread.
+ */
+void umh_wq_put_token(int token)
+{
+ struct umh_wq_entry *entry;
+
+ if (!token)
+ return;
+
+ spin_lock(&umh_wq_hash_lock);
+ entry = umh_wq_find_entry(token);
+ if (unlikely(IS_ERR(entry)))
+ spin_unlock(&umh_wq_hash_lock);
+ else {
+ if (--entry->count)
+ spin_unlock(&umh_wq_hash_lock);
+ else {
+ hlist_del(&entry->umh_wq_hlist);
+ spin_unlock(&umh_wq_hash_lock);
+ destroy_workqueue(entry->wq);
+ kfree(entry);
+ }
+ }
+ return;
+}
+EXPORT_SYMBOL(umh_wq_put_token);
+
/**
* call_usermodehelper_setup - prepare to call a usermode helper
* @path: path to usermode executable
@@ -689,6 +865,7 @@ struct ctl_table usermodehelper_table[] = {
void __init usermodehelper_init(void)
{
- khelper_wq = create_singlethread_workqueue("khelper");
+ umh_wq_hash_init();
+ khelper_wq = create_singlethread_workqueue(KHELPER);
BUG_ON(!khelper_wq);
}
--
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