linux-stable/kernel/vhost_task.c
Mike Christie db5247d9bf vhost_task: Handle SIGKILL by flushing work and exiting
Instead of lingering until the device is closed, this has us handle
SIGKILL by:

1. marking the worker as killed so we no longer try to use it with
   new virtqueues and new flush operations.
2. setting the virtqueue to worker mapping so no new works are queued.
3. running all the exiting works.

Suggested-by: Edward Adam Davis <eadavis@qq.com>
Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com
Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20240316004707.45557-9-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-05-22 08:31:15 -04:00

164 lines
3.7 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2021 Oracle Corporation
*/
#include <linux/slab.h>
#include <linux/completion.h>
#include <linux/sched/task.h>
#include <linux/sched/vhost_task.h>
#include <linux/sched/signal.h>
enum vhost_task_flags {
VHOST_TASK_FLAGS_STOP,
VHOST_TASK_FLAGS_KILLED,
};
struct vhost_task {
bool (*fn)(void *data);
void (*handle_sigkill)(void *data);
void *data;
struct completion exited;
unsigned long flags;
struct task_struct *task;
/* serialize SIGKILL and vhost_task_stop calls */
struct mutex exit_mutex;
};
static int vhost_task_fn(void *data)
{
struct vhost_task *vtsk = data;
for (;;) {
bool did_work;
if (signal_pending(current)) {
struct ksignal ksig;
if (get_signal(&ksig))
break;
}
/* mb paired w/ vhost_task_stop */
set_current_state(TASK_INTERRUPTIBLE);
if (test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) {
__set_current_state(TASK_RUNNING);
break;
}
did_work = vtsk->fn(vtsk->data);
if (!did_work)
schedule();
}
mutex_lock(&vtsk->exit_mutex);
/*
* If a vhost_task_stop and SIGKILL race, we can ignore the SIGKILL.
* When the vhost layer has called vhost_task_stop it's already stopped
* new work and flushed.
*/
if (!test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) {
set_bit(VHOST_TASK_FLAGS_KILLED, &vtsk->flags);
vtsk->handle_sigkill(vtsk->data);
}
mutex_unlock(&vtsk->exit_mutex);
complete(&vtsk->exited);
do_exit(0);
}
/**
* vhost_task_wake - wakeup the vhost_task
* @vtsk: vhost_task to wake
*
* wake up the vhost_task worker thread
*/
void vhost_task_wake(struct vhost_task *vtsk)
{
wake_up_process(vtsk->task);
}
EXPORT_SYMBOL_GPL(vhost_task_wake);
/**
* vhost_task_stop - stop a vhost_task
* @vtsk: vhost_task to stop
*
* vhost_task_fn ensures the worker thread exits after
* VHOST_TASK_FLAGS_STOP becomes true.
*/
void vhost_task_stop(struct vhost_task *vtsk)
{
mutex_lock(&vtsk->exit_mutex);
if (!test_bit(VHOST_TASK_FLAGS_KILLED, &vtsk->flags)) {
set_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);
vhost_task_wake(vtsk);
}
mutex_unlock(&vtsk->exit_mutex);
/*
* Make sure vhost_task_fn is no longer accessing the vhost_task before
* freeing it below.
*/
wait_for_completion(&vtsk->exited);
kfree(vtsk);
}
EXPORT_SYMBOL_GPL(vhost_task_stop);
/**
* vhost_task_create - create a copy of a task to be used by the kernel
* @fn: vhost worker function
* @handle_sigkill: vhost function to handle when we are killed
* @arg: data to be passed to fn and handled_kill
* @name: the thread's name
*
* This returns a specialized task for use by the vhost layer or NULL on
* failure. The returned task is inactive, and the caller must fire it up
* through vhost_task_start().
*/
struct vhost_task *vhost_task_create(bool (*fn)(void *),
void (*handle_sigkill)(void *), void *arg,
const char *name)
{
struct kernel_clone_args args = {
.flags = CLONE_FS | CLONE_UNTRACED | CLONE_VM |
CLONE_THREAD | CLONE_SIGHAND,
.exit_signal = 0,
.fn = vhost_task_fn,
.name = name,
.user_worker = 1,
.no_files = 1,
};
struct vhost_task *vtsk;
struct task_struct *tsk;
vtsk = kzalloc(sizeof(*vtsk), GFP_KERNEL);
if (!vtsk)
return NULL;
init_completion(&vtsk->exited);
mutex_init(&vtsk->exit_mutex);
vtsk->data = arg;
vtsk->fn = fn;
vtsk->handle_sigkill = handle_sigkill;
args.fn_arg = vtsk;
tsk = copy_process(NULL, 0, NUMA_NO_NODE, &args);
if (IS_ERR(tsk)) {
kfree(vtsk);
return NULL;
}
vtsk->task = tsk;
return vtsk;
}
EXPORT_SYMBOL_GPL(vhost_task_create);
/**
* vhost_task_start - start a vhost_task created with vhost_task_create
* @vtsk: vhost_task to wake up
*/
void vhost_task_start(struct vhost_task *vtsk)
{
wake_up_new_task(vtsk->task);
}
EXPORT_SYMBOL_GPL(vhost_task_start);