Author | Tokens | Token Proportion | Commits | Commit Proportion |
---|---|---|---|---|
Johannes Berg | 1112 | 79.09% | 3 | 25.00% |
Aviya Erenfeld | 145 | 10.31% | 1 | 8.33% |
Mukesh Ojha | 107 | 7.61% | 1 | 8.33% |
Greg Kroah-Hartman | 22 | 1.56% | 2 | 16.67% |
Arnd Bergmann | 9 | 0.64% | 1 | 8.33% |
Akinobu Mita | 8 | 0.57% | 2 | 16.67% |
Pierre-Louis Bossart | 2 | 0.14% | 1 | 8.33% |
Joe Perches | 1 | 0.07% | 1 | 8.33% |
Total | 1406 | 12 |
// SPDX-License-Identifier: GPL-2.0 /* * Copyright(c) 2014 Intel Mobile Communications GmbH * Copyright(c) 2015 Intel Deutschland GmbH * * Author: Johannes Berg <johannes@sipsolutions.net> */ #include <linux/module.h> #include <linux/device.h> #include <linux/devcoredump.h> #include <linux/list.h> #include <linux/slab.h> #include <linux/fs.h> #include <linux/workqueue.h> static struct class devcd_class; /* global disable flag, for security purposes */ static bool devcd_disabled; /* if data isn't read by userspace after 5 minutes then delete it */ #define DEVCD_TIMEOUT (HZ * 60 * 5) struct devcd_entry { struct device devcd_dev; void *data; size_t datalen; /* * Here, mutex is required to serialize the calls to del_wk work between * user/kernel space which happens when devcd is added with device_add() * and that sends uevent to user space. User space reads the uevents, * and calls to devcd_data_write() which try to modify the work which is * not even initialized/queued from devcoredump. * * * * cpu0(X) cpu1(Y) * * dev_coredump() uevent sent to user space * device_add() ======================> user space process Y reads the * uevents writes to devcd fd * which results into writes to * * devcd_data_write() * mod_delayed_work() * try_to_grab_pending() * del_timer() * debug_assert_init() * INIT_DELAYED_WORK() * schedule_delayed_work() * * * Also, mutex alone would not be enough to avoid scheduling of * del_wk work after it get flush from a call to devcd_free() * mentioned as below. * * disabled_store() * devcd_free() * mutex_lock() devcd_data_write() * flush_delayed_work() * mutex_unlock() * mutex_lock() * mod_delayed_work() * mutex_unlock() * So, delete_work flag is required. */ struct mutex mutex; bool delete_work; struct module *owner; ssize_t (*read)(char *buffer, loff_t offset, size_t count, void *data, size_t datalen); void (*free)(void *data); struct delayed_work del_wk; struct device *failing_dev; }; static struct devcd_entry *dev_to_devcd(struct device *dev) { return container_of(dev, struct devcd_entry, devcd_dev); } static void devcd_dev_release(struct device *dev) { struct devcd_entry *devcd = dev_to_devcd(dev); devcd->free(devcd->data); module_put(devcd->owner); /* * this seems racy, but I don't see a notifier or such on * a struct device to know when it goes away? */ if (devcd->failing_dev->kobj.sd) sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj, "devcoredump"); put_device(devcd->failing_dev); kfree(devcd); } static void devcd_del(struct work_struct *wk) { struct devcd_entry *devcd; devcd = container_of(wk, struct devcd_entry, del_wk.work); device_del(&devcd->devcd_dev); put_device(&devcd->devcd_dev); } static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj, struct bin_attribute *bin_attr, char *buffer, loff_t offset, size_t count) { struct device *dev = kobj_to_dev(kobj); struct devcd_entry *devcd = dev_to_devcd(dev); return devcd->read(buffer, offset, count, devcd->data, devcd->datalen); } static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj, struct bin_attribute *bin_attr, char *buffer, loff_t offset, size_t count) { struct device *dev = kobj_to_dev(kobj); struct devcd_entry *devcd = dev_to_devcd(dev); mutex_lock(&devcd->mutex); if (!devcd->delete_work) { devcd->delete_work = true; mod_delayed_work(system_wq, &devcd->del_wk, 0); } mutex_unlock(&devcd->mutex); return count; } static struct bin_attribute devcd_attr_data = { .attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, }, .size = 0, .read = devcd_data_read, .write = devcd_data_write, }; static struct bin_attribute *devcd_dev_bin_attrs[] = { &devcd_attr_data, NULL, }; static const struct attribute_group devcd_dev_group = { .bin_attrs = devcd_dev_bin_attrs, }; static const struct attribute_group *devcd_dev_groups[] = { &devcd_dev_group, NULL, }; static int devcd_free(struct device *dev, void *data) { struct devcd_entry *devcd = dev_to_devcd(dev); mutex_lock(&devcd->mutex); if (!devcd->delete_work) devcd->delete_work = true; flush_delayed_work(&devcd->del_wk); mutex_unlock(&devcd->mutex); return 0; } static ssize_t disabled_show(struct class *class, struct class_attribute *attr, char *buf) { return sysfs_emit(buf, "%d\n", devcd_disabled); } /* * * disabled_store() worker() * class_for_each_device(&devcd_class, * NULL, NULL, devcd_free) * ... * ... * while ((dev = class_dev_iter_next(&iter)) * devcd_del() * device_del() * put_device() <- last reference * error = fn(dev, data) devcd_dev_release() * devcd_free(dev, data) kfree(devcd) * mutex_lock(&devcd->mutex); * * * In the above diagram, It looks like disabled_store() would be racing with parallely * running devcd_del() and result in memory abort while acquiring devcd->mutex which * is called after kfree of devcd memory after dropping its last reference with * put_device(). However, this will not happens as fn(dev, data) runs * with its own reference to device via klist_node so it is not its last reference. * so, above situation would not occur. */ static ssize_t disabled_store(struct class *class, struct class_attribute *attr, const char *buf, size_t count) { long tmp = simple_strtol(buf, NULL, 10); /* * This essentially makes the attribute write-once, since you can't * go back to not having it disabled. This is intentional, it serves * as a system lockdown feature. */ if (tmp != 1) return -EINVAL; devcd_disabled = true; class_for_each_device(&devcd_class, NULL, NULL, devcd_free); return count; } static CLASS_ATTR_RW(disabled); static struct attribute *devcd_class_attrs[] = { &class_attr_disabled.attr, NULL, }; ATTRIBUTE_GROUPS(devcd_class); static struct class devcd_class = { .name = "devcoredump", .owner = THIS_MODULE, .dev_release = devcd_dev_release, .dev_groups = devcd_dev_groups, .class_groups = devcd_class_groups, }; static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count, void *data, size_t datalen) { return memory_read_from_buffer(buffer, count, &offset, data, datalen); } static void devcd_freev(void *data) { vfree(data); } /** * dev_coredumpv - create device coredump with vmalloc data * @dev: the struct device for the crashed device * @data: vmalloc data containing the device coredump * @datalen: length of the data * @gfp: allocation flags * * This function takes ownership of the vmalloc'ed data and will free * it when it is no longer used. See dev_coredumpm() for more information. */ void dev_coredumpv(struct device *dev, void *data, size_t datalen, gfp_t gfp) { dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev); } EXPORT_SYMBOL_GPL(dev_coredumpv); static int devcd_match_failing(struct device *dev, const void *failing) { struct devcd_entry *devcd = dev_to_devcd(dev); return devcd->failing_dev == failing; } /** * devcd_free_sgtable - free all the memory of the given scatterlist table * (i.e. both pages and scatterlist instances) * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained * using the sg_chain function then that function should be called only once * on the chained table * @data: pointer to sg_table to free */ static void devcd_free_sgtable(void *data) { _devcd_free_sgtable(data); } /** * devcd_read_from_sgtable - copy data from sg_table to a given buffer * and return the number of bytes read * @buffer: the buffer to copy the data to it * @buf_len: the length of the buffer * @data: the scatterlist table to copy from * @offset: start copy from @offset@ bytes from the head of the data * in the given scatterlist * @data_len: the length of the data in the sg_table */ static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset, size_t buf_len, void *data, size_t data_len) { struct scatterlist *table = data; if (offset > data_len) return -EINVAL; if (offset + buf_len > data_len) buf_len = data_len - offset; return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len, offset); } /** * dev_coredumpm - create device coredump with read/free methods * @dev: the struct device for the crashed device * @owner: the module that contains the read/free functions, use %THIS_MODULE * @data: data cookie for the @read/@free functions * @datalen: length of the data * @gfp: allocation flags * @read: function to read from the given buffer * @free: function to free the given buffer * * Creates a new device coredump for the given device. If a previous one hasn't * been read yet, the new coredump is discarded. The data lifetime is determined * by the device coredump framework and when it is no longer needed the @free * function will be called to free the data. */ void dev_coredumpm(struct device *dev, struct module *owner, void *data, size_t datalen, gfp_t gfp, ssize_t (*read)(char *buffer, loff_t offset, size_t count, void *data, size_t datalen), void (*free)(void *data)) { static atomic_t devcd_count = ATOMIC_INIT(0); struct devcd_entry *devcd; struct device *existing; if (devcd_disabled) goto free; existing = class_find_device(&devcd_class, NULL, dev, devcd_match_failing); if (existing) { put_device(existing); goto free; } if (!try_module_get(owner)) goto free; devcd = kzalloc(sizeof(*devcd), gfp); if (!devcd) goto put_module; devcd->owner = owner; devcd->data = data; devcd->datalen = datalen; devcd->read = read; devcd->free = free; devcd->failing_dev = get_device(dev); devcd->delete_work = false; mutex_init(&devcd->mutex); device_initialize(&devcd->devcd_dev); dev_set_name(&devcd->devcd_dev, "devcd%d", atomic_inc_return(&devcd_count)); devcd->devcd_dev.class = &devcd_class; mutex_lock(&devcd->mutex); if (device_add(&devcd->devcd_dev)) goto put_device; /* * These should normally not fail, but there is no problem * continuing without the links, so just warn instead of * failing. */ if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj, "failing_device") || sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj, "devcoredump")) dev_warn(dev, "devcoredump create_link failed\n"); INIT_DELAYED_WORK(&devcd->del_wk, devcd_del); schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT); mutex_unlock(&devcd->mutex); return; put_device: put_device(&devcd->devcd_dev); mutex_unlock(&devcd->mutex); put_module: module_put(owner); free: free(data); } EXPORT_SYMBOL_GPL(dev_coredumpm); /** * dev_coredumpsg - create device coredump that uses scatterlist as data * parameter * @dev: the struct device for the crashed device * @table: the dump data * @datalen: length of the data * @gfp: allocation flags * * Creates a new device coredump for the given device. If a previous one hasn't * been read yet, the new coredump is discarded. The data lifetime is determined * by the device coredump framework and when it is no longer needed * it will free the data. */ void dev_coredumpsg(struct device *dev, struct scatterlist *table, size_t datalen, gfp_t gfp) { dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable, devcd_free_sgtable); } EXPORT_SYMBOL_GPL(dev_coredumpsg); static int __init devcoredump_init(void) { return class_register(&devcd_class); } __initcall(devcoredump_init); static void __exit devcoredump_exit(void) { class_for_each_device(&devcd_class, NULL, NULL, devcd_free); class_unregister(&devcd_class); } __exitcall(devcoredump_exit);
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