429 lines
12 KiB
C
429 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright(c) 2014 Intel Mobile Communications GmbH
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* Copyright(c) 2015 Intel Deutschland GmbH
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*
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* Author: Johannes Berg <johannes@sipsolutions.net>
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*/
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/devcoredump.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/workqueue.h>
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static struct class devcd_class;
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/* global disable flag, for security purposes */
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static bool devcd_disabled;
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/* if data isn't read by userspace after 5 minutes then delete it */
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#define DEVCD_TIMEOUT (HZ * 60 * 5)
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struct devcd_entry {
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struct device devcd_dev;
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void *data;
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size_t datalen;
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/*
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* Here, mutex is required to serialize the calls to del_wk work between
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* user/kernel space which happens when devcd is added with device_add()
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* and that sends uevent to user space. User space reads the uevents,
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* and calls to devcd_data_write() which try to modify the work which is
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* not even initialized/queued from devcoredump.
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*
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*
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*
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* cpu0(X) cpu1(Y)
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*
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* dev_coredump() uevent sent to user space
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* device_add() ======================> user space process Y reads the
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* uevents writes to devcd fd
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* which results into writes to
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*
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* devcd_data_write()
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* mod_delayed_work()
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* try_to_grab_pending()
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* del_timer()
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* debug_assert_init()
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* INIT_DELAYED_WORK()
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* schedule_delayed_work()
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*
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*
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* Also, mutex alone would not be enough to avoid scheduling of
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* del_wk work after it get flush from a call to devcd_free()
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* mentioned as below.
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*
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* disabled_store()
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* devcd_free()
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* mutex_lock() devcd_data_write()
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* flush_delayed_work()
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* mutex_unlock()
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* mutex_lock()
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* mod_delayed_work()
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* mutex_unlock()
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* So, delete_work flag is required.
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*/
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struct mutex mutex;
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bool delete_work;
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struct module *owner;
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ssize_t (*read)(char *buffer, loff_t offset, size_t count,
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void *data, size_t datalen);
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void (*free)(void *data);
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struct delayed_work del_wk;
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struct device *failing_dev;
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};
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static struct devcd_entry *dev_to_devcd(struct device *dev)
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{
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return container_of(dev, struct devcd_entry, devcd_dev);
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}
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static void devcd_dev_release(struct device *dev)
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{
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struct devcd_entry *devcd = dev_to_devcd(dev);
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devcd->free(devcd->data);
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module_put(devcd->owner);
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/*
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* this seems racy, but I don't see a notifier or such on
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* a struct device to know when it goes away?
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*/
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if (devcd->failing_dev->kobj.sd)
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sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
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"devcoredump");
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put_device(devcd->failing_dev);
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kfree(devcd);
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}
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static void devcd_del(struct work_struct *wk)
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{
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struct devcd_entry *devcd;
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devcd = container_of(wk, struct devcd_entry, del_wk.work);
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device_del(&devcd->devcd_dev);
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put_device(&devcd->devcd_dev);
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}
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static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
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struct bin_attribute *bin_attr,
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char *buffer, loff_t offset, size_t count)
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{
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struct device *dev = kobj_to_dev(kobj);
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struct devcd_entry *devcd = dev_to_devcd(dev);
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return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
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}
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static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
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struct bin_attribute *bin_attr,
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char *buffer, loff_t offset, size_t count)
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{
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struct device *dev = kobj_to_dev(kobj);
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struct devcd_entry *devcd = dev_to_devcd(dev);
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mutex_lock(&devcd->mutex);
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if (!devcd->delete_work) {
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devcd->delete_work = true;
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mod_delayed_work(system_wq, &devcd->del_wk, 0);
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}
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mutex_unlock(&devcd->mutex);
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return count;
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}
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static struct bin_attribute devcd_attr_data = {
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.attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
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.size = 0,
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.read = devcd_data_read,
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.write = devcd_data_write,
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};
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static struct bin_attribute *devcd_dev_bin_attrs[] = {
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&devcd_attr_data, NULL,
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};
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static const struct attribute_group devcd_dev_group = {
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.bin_attrs = devcd_dev_bin_attrs,
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};
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static const struct attribute_group *devcd_dev_groups[] = {
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&devcd_dev_group, NULL,
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};
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static int devcd_free(struct device *dev, void *data)
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{
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struct devcd_entry *devcd = dev_to_devcd(dev);
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mutex_lock(&devcd->mutex);
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if (!devcd->delete_work)
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devcd->delete_work = true;
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flush_delayed_work(&devcd->del_wk);
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mutex_unlock(&devcd->mutex);
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return 0;
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}
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static ssize_t disabled_show(const struct class *class, const struct class_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%d\n", devcd_disabled);
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}
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/*
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*
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* disabled_store() worker()
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* class_for_each_device(&devcd_class,
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* NULL, NULL, devcd_free)
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* ...
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* ...
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* while ((dev = class_dev_iter_next(&iter))
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* devcd_del()
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* device_del()
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* put_device() <- last reference
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* error = fn(dev, data) devcd_dev_release()
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* devcd_free(dev, data) kfree(devcd)
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* mutex_lock(&devcd->mutex);
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*
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*
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* In the above diagram, It looks like disabled_store() would be racing with parallely
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* running devcd_del() and result in memory abort while acquiring devcd->mutex which
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* is called after kfree of devcd memory after dropping its last reference with
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* put_device(). However, this will not happens as fn(dev, data) runs
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* with its own reference to device via klist_node so it is not its last reference.
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* so, above situation would not occur.
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*/
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static ssize_t disabled_store(const struct class *class, const struct class_attribute *attr,
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const char *buf, size_t count)
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{
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long tmp = simple_strtol(buf, NULL, 10);
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/*
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* This essentially makes the attribute write-once, since you can't
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* go back to not having it disabled. This is intentional, it serves
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* as a system lockdown feature.
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*/
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if (tmp != 1)
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return -EINVAL;
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devcd_disabled = true;
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class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
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return count;
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}
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static CLASS_ATTR_RW(disabled);
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static struct attribute *devcd_class_attrs[] = {
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&class_attr_disabled.attr,
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NULL,
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};
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ATTRIBUTE_GROUPS(devcd_class);
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static struct class devcd_class = {
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.name = "devcoredump",
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.dev_release = devcd_dev_release,
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.dev_groups = devcd_dev_groups,
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.class_groups = devcd_class_groups,
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};
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static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
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void *data, size_t datalen)
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{
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return memory_read_from_buffer(buffer, count, &offset, data, datalen);
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}
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static void devcd_freev(void *data)
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{
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vfree(data);
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}
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/**
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* dev_coredumpv - create device coredump with vmalloc data
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* @dev: the struct device for the crashed device
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* @data: vmalloc data containing the device coredump
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* @datalen: length of the data
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* @gfp: allocation flags
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*
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* This function takes ownership of the vmalloc'ed data and will free
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* it when it is no longer used. See dev_coredumpm() for more information.
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*/
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void dev_coredumpv(struct device *dev, void *data, size_t datalen,
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gfp_t gfp)
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{
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dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
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}
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EXPORT_SYMBOL_GPL(dev_coredumpv);
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static int devcd_match_failing(struct device *dev, const void *failing)
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{
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struct devcd_entry *devcd = dev_to_devcd(dev);
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return devcd->failing_dev == failing;
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}
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/**
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* devcd_free_sgtable - free all the memory of the given scatterlist table
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* (i.e. both pages and scatterlist instances)
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* NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
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* using the sg_chain function then that function should be called only once
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* on the chained table
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* @data: pointer to sg_table to free
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*/
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static void devcd_free_sgtable(void *data)
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{
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_devcd_free_sgtable(data);
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}
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/**
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* devcd_read_from_sgtable - copy data from sg_table to a given buffer
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* and return the number of bytes read
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* @buffer: the buffer to copy the data to it
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* @buf_len: the length of the buffer
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* @data: the scatterlist table to copy from
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* @offset: start copy from @offset@ bytes from the head of the data
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* in the given scatterlist
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* @data_len: the length of the data in the sg_table
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*/
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static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
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size_t buf_len, void *data,
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size_t data_len)
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{
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struct scatterlist *table = data;
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if (offset > data_len)
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return -EINVAL;
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if (offset + buf_len > data_len)
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buf_len = data_len - offset;
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return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
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offset);
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}
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/**
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* dev_coredumpm - create device coredump with read/free methods
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* @dev: the struct device for the crashed device
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* @owner: the module that contains the read/free functions, use %THIS_MODULE
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* @data: data cookie for the @read/@free functions
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* @datalen: length of the data
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* @gfp: allocation flags
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* @read: function to read from the given buffer
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* @free: function to free the given buffer
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*
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* Creates a new device coredump for the given device. If a previous one hasn't
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* been read yet, the new coredump is discarded. The data lifetime is determined
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* by the device coredump framework and when it is no longer needed the @free
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* function will be called to free the data.
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*/
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void dev_coredumpm(struct device *dev, struct module *owner,
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void *data, size_t datalen, gfp_t gfp,
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ssize_t (*read)(char *buffer, loff_t offset, size_t count,
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void *data, size_t datalen),
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void (*free)(void *data))
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{
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static atomic_t devcd_count = ATOMIC_INIT(0);
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struct devcd_entry *devcd;
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struct device *existing;
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if (devcd_disabled)
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goto free;
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existing = class_find_device(&devcd_class, NULL, dev,
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devcd_match_failing);
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if (existing) {
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put_device(existing);
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goto free;
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}
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if (!try_module_get(owner))
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goto free;
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devcd = kzalloc(sizeof(*devcd), gfp);
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if (!devcd)
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goto put_module;
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devcd->owner = owner;
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devcd->data = data;
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devcd->datalen = datalen;
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devcd->read = read;
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devcd->free = free;
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devcd->failing_dev = get_device(dev);
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devcd->delete_work = false;
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mutex_init(&devcd->mutex);
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device_initialize(&devcd->devcd_dev);
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dev_set_name(&devcd->devcd_dev, "devcd%d",
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atomic_inc_return(&devcd_count));
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devcd->devcd_dev.class = &devcd_class;
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mutex_lock(&devcd->mutex);
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dev_set_uevent_suppress(&devcd->devcd_dev, true);
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if (device_add(&devcd->devcd_dev))
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goto put_device;
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/*
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* These should normally not fail, but there is no problem
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* continuing without the links, so just warn instead of
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* failing.
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*/
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if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
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"failing_device") ||
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sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
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"devcoredump"))
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dev_warn(dev, "devcoredump create_link failed\n");
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dev_set_uevent_suppress(&devcd->devcd_dev, false);
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kobject_uevent(&devcd->devcd_dev.kobj, KOBJ_ADD);
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INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
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schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
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mutex_unlock(&devcd->mutex);
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return;
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put_device:
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put_device(&devcd->devcd_dev);
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mutex_unlock(&devcd->mutex);
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put_module:
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module_put(owner);
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free:
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free(data);
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}
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EXPORT_SYMBOL_GPL(dev_coredumpm);
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/**
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* dev_coredumpsg - create device coredump that uses scatterlist as data
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* parameter
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* @dev: the struct device for the crashed device
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* @table: the dump data
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* @datalen: length of the data
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* @gfp: allocation flags
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*
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* Creates a new device coredump for the given device. If a previous one hasn't
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* been read yet, the new coredump is discarded. The data lifetime is determined
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* by the device coredump framework and when it is no longer needed
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* it will free the data.
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*/
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void dev_coredumpsg(struct device *dev, struct scatterlist *table,
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size_t datalen, gfp_t gfp)
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{
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dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
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devcd_free_sgtable);
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}
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EXPORT_SYMBOL_GPL(dev_coredumpsg);
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static int __init devcoredump_init(void)
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{
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return class_register(&devcd_class);
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}
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__initcall(devcoredump_init);
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static void __exit devcoredump_exit(void)
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{
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class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
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class_unregister(&devcd_class);
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}
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__exitcall(devcoredump_exit);
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