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Date: Tue, 31 Mar 2015 11:14:50 +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 2/7] kmod - teach usermodehelper to use service
workqueues
The call_usermodehelper() function executes all binaries in the
global "init" root context. This doesn't allow a binary to be run
within a namespace environment such as a container. To do this
the namespace environment of the contaner must be available to
provide the required execution environment.
This can be done by creating a service thread, identified by
issuing a token identifier, used when executing the helper
with a function that takes the token as a parameter.
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 | 5 +++++
kernel/kmod.c | 38 +++++++++++++++++++++++++++++++-------
2 files changed, 36 insertions(+), 7 deletions(-)
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index fa46722..9a9fcb3 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -56,6 +56,7 @@ struct file;
struct subprocess_info {
struct work_struct work;
struct completion *complete;
+ int wq_token;
char *path;
char **argv;
char **envp;
@@ -72,6 +73,10 @@ extern void umh_wq_put_token(int token);
extern int
call_usermodehelper(char *path, char **argv, char **envp, int wait);
+extern int
+call_usermodehelper_service(char *path, char **argv,
+ char **envp, int token, int wait);
+
extern struct subprocess_info *
call_usermodehelper_setup(char *path, char **argv, char **envp, gfp_t gfp_mask,
int (*init)(struct subprocess_info *info, struct cred *new),
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 55d20ce..47c5ff5 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -712,6 +712,7 @@ EXPORT_SYMBOL(call_usermodehelper_setup);
*/
int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
{
+ static struct workqueue_struct *wq;
DECLARE_COMPLETION_ONSTACK(done);
int retval = 0;
@@ -720,7 +721,8 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
return -EINVAL;
}
helper_lock();
- if (!khelper_wq || usermodehelper_disabled) {
+ wq = umh_find_wq(sub_info->wq_token, wait);
+ if (!wq || usermodehelper_disabled) {
retval = -EBUSY;
goto out;
}
@@ -732,7 +734,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
sub_info->wait = wait;
- queue_work(khelper_wq, &sub_info->work);
+ queue_work(wq, &sub_info->work);
if (wait == UMH_NO_WAIT) /* task has freed sub_info */
goto unlock;
@@ -759,19 +761,21 @@ unlock:
EXPORT_SYMBOL(call_usermodehelper_exec);
/**
- * call_usermodehelper() - prepare and start a usermode application
+ * call_usermodehelper_service() - start a usermode application within
+ * a service environment.
* @path: path to usermode executable
* @argv: arg vector for process
* @envp: environment for process
+ * @token: token corresponding to a service environment obtained by a
+ * call to umh_wq_get_token().
* @wait: wait for the application to finish and return status.
* when UMH_NO_WAIT don't wait at all, but you get no useful error back
* when the program couldn't be exec'ed. This makes it safe to call
* from interrupt context.
- *
- * This function is the equivalent to use call_usermodehelper_setup() and
- * call_usermodehelper_exec().
*/
-int call_usermodehelper(char *path, char **argv, char **envp, int wait)
+int call_usermodehelper_service(char *path,
+ char **argv, char **envp,
+ int token, int wait)
{
struct subprocess_info *info;
gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
@@ -780,9 +784,29 @@ int call_usermodehelper(char *path, char **argv, char **envp, int wait)
NULL, NULL, NULL);
if (info == NULL)
return -ENOMEM;
+ info->wq_token = token;
return call_usermodehelper_exec(info, wait);
}
+EXPORT_SYMBOL(call_usermodehelper_service);
+
+/**
+ * call_usermodehelper() - prepare and start a usermode application
+ * @path: path to usermode executable
+ * @argv: arg vector for process
+ * @envp: environment for process
+ * @wait: wait for the application to finish and return status.
+ * when UMH_NO_WAIT don't wait at all, but you get no useful error back
+ * when the program couldn't be exec'ed. This makes it safe to call
+ * from interrupt context.
+ *
+ * This function is the equivalent to using call_usermodehelper_setup() and
+ * call_usermodehelper_exec().
+ */
+int call_usermodehelper(char *path, char **argv, char **envp, int wait)
+{
+ return call_usermodehelper_service(path, argv, envp, 0, wait);
+}
EXPORT_SYMBOL(call_usermodehelper);
static int proc_cap_handler(struct ctl_table *table, int write,
--
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