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Date: Wed, 23 Jun 2021 22:08:02 -0500
From: Mike Christie <michael.christie@...cle.com>
To: linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org, mst@...hat.com,
sgarzare@...hat.com, jasowang@...hat.com, stefanha@...hat.com,
christian@...uner.io, akpm@...ux-foundation.org,
peterz@...radead.org, christian.brauner@...ntu.com
Cc: Mike Christie <michael.christie@...cle.com>
Subject: [PATCH 1/3] kthread: allow caller to pass in user_struct
Currently, the kthreadd's user_struct has its processes checked against
the RLIMIT_NPROC limit. In cases like for vhost where the driver is making
a thread for userspace, we want the userspace process to have its processes
count checked and incremented.
This patch allows the kthread code to take a user_struct and pass it to
copy_process. The next patches will then convert the fork/cred code.
Signed-off-by: Mike Christie <michael.christie@...cle.com>
---
include/linux/kthread.h | 5 ++++
include/linux/sched/task.h | 2 ++
kernel/kthread.c | 58 ++++++++++++++++++++++++++++++++------
3 files changed, 56 insertions(+), 9 deletions(-)
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 2484ed97e72f..3c64bd8bf34c 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -28,6 +28,11 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
kthread_create_on_node(threadfn, data, NUMA_NO_NODE, namefmt, ##arg)
+struct task_struct *kthread_create_for_user(int (*threadfn)(void *data),
+ void *data,
+ struct user_struct *user,
+ const char namefmt[], ...);
+
struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
void *data,
unsigned int cpu,
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index ef02be869cf2..357e95679e33 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -34,6 +34,8 @@ struct kernel_clone_args {
int io_thread;
struct cgroup *cgrp;
struct css_set *cset;
+ /* User to check RLIMIT_NPROC against */
+ struct user_struct *user;
};
/*
diff --git a/kernel/kthread.c b/kernel/kthread.c
index fe3f2a40d61e..9e7e4d04664f 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -41,6 +41,7 @@ struct kthread_create_info
int (*threadfn)(void *data);
void *data;
int node;
+ struct user_struct *user;
/* Result passed back to kthread_create() from kthreadd. */
struct task_struct *result;
@@ -327,13 +328,21 @@ int tsk_fork_get_node(struct task_struct *tsk)
static void create_kthread(struct kthread_create_info *create)
{
+ /* We want our own signal handler (we take no signals by default). */
+ struct kernel_clone_args clone_args = {
+ .flags = CLONE_FS | CLONE_FILES | CLONE_VM |
+ CLONE_UNTRACED,
+ .exit_signal = SIGCHLD,
+ .stack = (unsigned long)kthread,
+ .stack_size = (unsigned long)create,
+ .user = create->user,
+ };
int pid;
#ifdef CONFIG_NUMA
current->pref_node_fork = create->node;
#endif
- /* We want our own signal handler (we take no signals by default). */
- pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
+ pid = kernel_clone(&clone_args);
if (pid < 0) {
/* If user was SIGKILLed, I release the structure. */
struct completion *done = xchg(&create->done, NULL);
@@ -347,11 +356,11 @@ static void create_kthread(struct kthread_create_info *create)
}
}
-static __printf(4, 0)
+static __printf(5, 0)
struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
- void *data, int node,
- const char namefmt[],
- va_list args)
+ void *data, int node,
+ struct user_struct *user,
+ const char namefmt[], va_list args)
{
DECLARE_COMPLETION_ONSTACK(done);
struct task_struct *task;
@@ -364,6 +373,7 @@ struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
create->data = data;
create->node = node;
create->done = &done;
+ create->user = user;
spin_lock(&kthread_create_lock);
list_add_tail(&create->list, &kthread_create_list);
@@ -444,13 +454,43 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
va_list args;
va_start(args, namefmt);
- task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
+ task = __kthread_create_on_node(threadfn, data, node, NULL, namefmt,
+ args);
va_end(args);
return task;
}
EXPORT_SYMBOL(kthread_create_on_node);
+/**
+ * kthread_create_for_user - create a kthread and check @user's RLIMIT_NPROC
+ * @threadfn: the function to run until signal_pending(current).
+ * @data: data ptr for @threadfn.
+ * @user: user_struct that will have its RLIMIT_NPROC checked
+ * @namefmt: printf-style name for the thread.
+ *
+ * This will create a kthread on the current node, leaving it in the stopped
+ * state. This is just a helper for kthread_create_on_node() that will check
+ * @user's process count against its RLIMIT_NPROC. See the
+ * kthread_create_on_node() documentation for more details.
+ */
+struct task_struct *kthread_create_for_user(int (*threadfn)(void *data),
+ void *data,
+ struct user_struct *user,
+ const char namefmt[], ...)
+{
+ struct task_struct *task;
+ va_list args;
+
+ va_start(args, namefmt);
+ task = __kthread_create_on_node(threadfn, data, NUMA_NO_NODE, user,
+ namefmt, args);
+ va_end(args);
+
+ return task;
+}
+EXPORT_SYMBOL(kthread_create_for_user);
+
static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
{
unsigned long flags;
@@ -785,8 +825,8 @@ __kthread_create_worker(int cpu, unsigned int flags,
if (cpu >= 0)
node = cpu_to_node(cpu);
- task = __kthread_create_on_node(kthread_worker_fn, worker,
- node, namefmt, args);
+ task = __kthread_create_on_node(kthread_worker_fn, worker, node, NULL,
+ namefmt, args);
if (IS_ERR(task))
goto fail_task;
--
2.25.1
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