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21ccc9cd72
When building the files in the tracefs file system, do not by default set any permissions for OTH (other). This will make it easier for admins who want to define a group for accessing tracefs and not having to first disable all the permission bits for "other" in the file system. As tracing can leak sensitive information, it should never by default allowing all users access. An admin can still set the permission bits for others to have access, which may be useful for creating a honeypot and seeing who takes advantage of it and roots the machine. Link: https://lkml.kernel.org/r/20210818153038.864149276@goodmis.org Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
487 lines
13 KiB
C
487 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Generic dynamic event control interface
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*
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* Copyright (C) 2018 Masami Hiramatsu <mhiramat@kernel.org>
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*/
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#include <linux/debugfs.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/mm.h>
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#include <linux/mutex.h>
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#include <linux/tracefs.h>
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#include "trace.h"
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#include "trace_output.h" /* for trace_event_sem */
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#include "trace_dynevent.h"
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static DEFINE_MUTEX(dyn_event_ops_mutex);
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static LIST_HEAD(dyn_event_ops_list);
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bool trace_event_dyn_try_get_ref(struct trace_event_call *dyn_call)
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{
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struct trace_event_call *call;
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bool ret = false;
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if (WARN_ON_ONCE(!(dyn_call->flags & TRACE_EVENT_FL_DYNAMIC)))
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return false;
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down_read(&trace_event_sem);
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list_for_each_entry(call, &ftrace_events, list) {
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if (call == dyn_call) {
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atomic_inc(&dyn_call->refcnt);
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ret = true;
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}
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}
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up_read(&trace_event_sem);
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return ret;
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}
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void trace_event_dyn_put_ref(struct trace_event_call *call)
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{
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if (WARN_ON_ONCE(!(call->flags & TRACE_EVENT_FL_DYNAMIC)))
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return;
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if (WARN_ON_ONCE(atomic_read(&call->refcnt) <= 0)) {
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atomic_set(&call->refcnt, 0);
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return;
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}
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atomic_dec(&call->refcnt);
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}
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bool trace_event_dyn_busy(struct trace_event_call *call)
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{
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return atomic_read(&call->refcnt) != 0;
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}
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int dyn_event_register(struct dyn_event_operations *ops)
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{
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if (!ops || !ops->create || !ops->show || !ops->is_busy ||
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!ops->free || !ops->match)
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return -EINVAL;
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INIT_LIST_HEAD(&ops->list);
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mutex_lock(&dyn_event_ops_mutex);
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list_add_tail(&ops->list, &dyn_event_ops_list);
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mutex_unlock(&dyn_event_ops_mutex);
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return 0;
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}
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int dyn_event_release(const char *raw_command, struct dyn_event_operations *type)
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{
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struct dyn_event *pos, *n;
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char *system = NULL, *event, *p;
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int argc, ret = -ENOENT;
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char **argv;
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argv = argv_split(GFP_KERNEL, raw_command, &argc);
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if (!argv)
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return -ENOMEM;
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if (argv[0][0] == '-') {
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if (argv[0][1] != ':') {
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ret = -EINVAL;
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goto out;
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}
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event = &argv[0][2];
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} else {
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event = strchr(argv[0], ':');
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if (!event) {
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ret = -EINVAL;
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goto out;
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}
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event++;
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}
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p = strchr(event, '/');
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if (p) {
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system = event;
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event = p + 1;
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*p = '\0';
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}
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if (event[0] == '\0') {
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ret = -EINVAL;
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goto out;
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}
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mutex_lock(&event_mutex);
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for_each_dyn_event_safe(pos, n) {
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if (type && type != pos->ops)
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continue;
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if (!pos->ops->match(system, event,
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argc - 1, (const char **)argv + 1, pos))
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continue;
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ret = pos->ops->free(pos);
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if (ret)
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break;
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}
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mutex_unlock(&event_mutex);
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out:
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argv_free(argv);
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return ret;
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}
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static int create_dyn_event(const char *raw_command)
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{
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struct dyn_event_operations *ops;
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int ret = -ENODEV;
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if (raw_command[0] == '-' || raw_command[0] == '!')
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return dyn_event_release(raw_command, NULL);
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mutex_lock(&dyn_event_ops_mutex);
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list_for_each_entry(ops, &dyn_event_ops_list, list) {
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ret = ops->create(raw_command);
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if (!ret || ret != -ECANCELED)
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break;
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}
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mutex_unlock(&dyn_event_ops_mutex);
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if (ret == -ECANCELED)
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ret = -EINVAL;
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return ret;
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}
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/* Protected by event_mutex */
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LIST_HEAD(dyn_event_list);
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void *dyn_event_seq_start(struct seq_file *m, loff_t *pos)
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{
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mutex_lock(&event_mutex);
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return seq_list_start(&dyn_event_list, *pos);
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}
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void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
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{
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return seq_list_next(v, &dyn_event_list, pos);
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}
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void dyn_event_seq_stop(struct seq_file *m, void *v)
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{
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mutex_unlock(&event_mutex);
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}
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static int dyn_event_seq_show(struct seq_file *m, void *v)
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{
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struct dyn_event *ev = v;
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if (ev && ev->ops)
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return ev->ops->show(m, ev);
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return 0;
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}
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static const struct seq_operations dyn_event_seq_op = {
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.start = dyn_event_seq_start,
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.next = dyn_event_seq_next,
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.stop = dyn_event_seq_stop,
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.show = dyn_event_seq_show
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};
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/*
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* dyn_events_release_all - Release all specific events
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* @type: the dyn_event_operations * which filters releasing events
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*
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* This releases all events which ->ops matches @type. If @type is NULL,
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* all events are released.
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* Return -EBUSY if any of them are in use, and return other errors when
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* it failed to free the given event. Except for -EBUSY, event releasing
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* process will be aborted at that point and there may be some other
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* releasable events on the list.
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*/
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int dyn_events_release_all(struct dyn_event_operations *type)
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{
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struct dyn_event *ev, *tmp;
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int ret = 0;
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mutex_lock(&event_mutex);
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for_each_dyn_event(ev) {
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if (type && ev->ops != type)
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continue;
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if (ev->ops->is_busy(ev)) {
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ret = -EBUSY;
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goto out;
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}
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}
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for_each_dyn_event_safe(ev, tmp) {
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if (type && ev->ops != type)
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continue;
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ret = ev->ops->free(ev);
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if (ret)
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break;
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}
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out:
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mutex_unlock(&event_mutex);
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return ret;
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}
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static int dyn_event_open(struct inode *inode, struct file *file)
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{
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int ret;
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ret = tracing_check_open_get_tr(NULL);
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if (ret)
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return ret;
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if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
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ret = dyn_events_release_all(NULL);
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if (ret < 0)
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return ret;
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}
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return seq_open(file, &dyn_event_seq_op);
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}
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static ssize_t dyn_event_write(struct file *file, const char __user *buffer,
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size_t count, loff_t *ppos)
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{
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return trace_parse_run_command(file, buffer, count, ppos,
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create_dyn_event);
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}
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static const struct file_operations dynamic_events_ops = {
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.owner = THIS_MODULE,
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.open = dyn_event_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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.write = dyn_event_write,
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};
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/* Make a tracefs interface for controlling dynamic events */
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static __init int init_dynamic_event(void)
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{
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struct dentry *entry;
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int ret;
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ret = tracing_init_dentry();
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if (ret)
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return 0;
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entry = tracefs_create_file("dynamic_events", TRACE_MODE_WRITE, NULL,
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NULL, &dynamic_events_ops);
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/* Event list interface */
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if (!entry)
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pr_warn("Could not create tracefs 'dynamic_events' entry\n");
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return 0;
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}
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fs_initcall(init_dynamic_event);
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/**
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* dynevent_arg_add - Add an arg to a dynevent_cmd
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* @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
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* @arg: The argument to append to the current cmd
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* @check_arg: An (optional) pointer to a function checking arg sanity
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*
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* Append an argument to a dynevent_cmd. The argument string will be
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* appended to the current cmd string, followed by a separator, if
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* applicable. Before the argument is added, the @check_arg function,
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* if present, will be used to check the sanity of the current arg
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* string.
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*
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* The cmd string and separator should be set using the
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* dynevent_arg_init() before any arguments are added using this
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* function.
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*
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* Return: 0 if successful, error otherwise.
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*/
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int dynevent_arg_add(struct dynevent_cmd *cmd,
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struct dynevent_arg *arg,
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dynevent_check_arg_fn_t check_arg)
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{
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int ret = 0;
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if (check_arg) {
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ret = check_arg(arg);
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if (ret)
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return ret;
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}
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ret = seq_buf_printf(&cmd->seq, " %s%c", arg->str, arg->separator);
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if (ret) {
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pr_err("String is too long: %s%c\n", arg->str, arg->separator);
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return -E2BIG;
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}
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return ret;
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}
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/**
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* dynevent_arg_pair_add - Add an arg pair to a dynevent_cmd
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* @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
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* @arg_pair: The argument pair to append to the current cmd
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* @check_arg: An (optional) pointer to a function checking arg sanity
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*
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* Append an argument pair to a dynevent_cmd. An argument pair
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* consists of a left-hand-side argument and a right-hand-side
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* argument separated by an operator, which can be whitespace, all
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* followed by a separator, if applicable. This can be used to add
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* arguments of the form 'type variable_name;' or 'x+y'.
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*
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* The lhs argument string will be appended to the current cmd string,
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* followed by an operator, if applicable, followed by the rhs string,
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* followed finally by a separator, if applicable. Before the
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* argument is added, the @check_arg function, if present, will be
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* used to check the sanity of the current arg strings.
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*
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* The cmd strings, operator, and separator should be set using the
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* dynevent_arg_pair_init() before any arguments are added using this
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* function.
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*
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* Return: 0 if successful, error otherwise.
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*/
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int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
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struct dynevent_arg_pair *arg_pair,
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dynevent_check_arg_fn_t check_arg)
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{
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int ret = 0;
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if (check_arg) {
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ret = check_arg(arg_pair);
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if (ret)
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return ret;
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}
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ret = seq_buf_printf(&cmd->seq, " %s%c%s%c", arg_pair->lhs,
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arg_pair->operator, arg_pair->rhs,
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arg_pair->separator);
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if (ret) {
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pr_err("field string is too long: %s%c%s%c\n", arg_pair->lhs,
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arg_pair->operator, arg_pair->rhs,
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arg_pair->separator);
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return -E2BIG;
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}
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return ret;
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}
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/**
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* dynevent_str_add - Add a string to a dynevent_cmd
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* @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
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* @str: The string to append to the current cmd
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*
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* Append a string to a dynevent_cmd. The string will be appended to
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* the current cmd string as-is, with nothing prepended or appended.
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*
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* Return: 0 if successful, error otherwise.
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*/
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int dynevent_str_add(struct dynevent_cmd *cmd, const char *str)
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{
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int ret = 0;
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ret = seq_buf_puts(&cmd->seq, str);
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if (ret) {
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pr_err("String is too long: %s\n", str);
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return -E2BIG;
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}
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return ret;
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}
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/**
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* dynevent_cmd_init - Initialize a dynevent_cmd object
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* @cmd: A pointer to the dynevent_cmd struct representing the cmd
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* @buf: A pointer to the buffer to generate the command into
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* @maxlen: The length of the buffer the command will be generated into
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* @type: The type of the cmd, checked against further operations
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* @run_command: The type-specific function that will actually run the command
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*
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* Initialize a dynevent_cmd. A dynevent_cmd is used to build up and
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* run dynamic event creation commands, such as commands for creating
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* synthetic and kprobe events. Before calling any of the functions
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* used to build the command, a dynevent_cmd object should be
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* instantiated and initialized using this function.
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*
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* The initialization sets things up by saving a pointer to the
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* user-supplied buffer and its length via the @buf and @maxlen
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* params, and by saving the cmd-specific @type and @run_command
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* params which are used to check subsequent dynevent_cmd operations
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* and actually run the command when complete.
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*/
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void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
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enum dynevent_type type,
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dynevent_create_fn_t run_command)
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{
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memset(cmd, '\0', sizeof(*cmd));
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seq_buf_init(&cmd->seq, buf, maxlen);
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cmd->type = type;
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cmd->run_command = run_command;
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}
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/**
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* dynevent_arg_init - Initialize a dynevent_arg object
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* @arg: A pointer to the dynevent_arg struct representing the arg
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* @separator: An (optional) separator, appended after adding the arg
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*
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* Initialize a dynevent_arg object. A dynevent_arg represents an
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* object used to append single arguments to the current command
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* string. After the arg string is successfully appended to the
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* command string, the optional @separator is appended. If no
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* separator was specified when initializing the arg, a space will be
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* appended.
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*/
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void dynevent_arg_init(struct dynevent_arg *arg,
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char separator)
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{
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memset(arg, '\0', sizeof(*arg));
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if (!separator)
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separator = ' ';
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arg->separator = separator;
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}
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/**
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* dynevent_arg_pair_init - Initialize a dynevent_arg_pair object
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* @arg_pair: A pointer to the dynevent_arg_pair struct representing the arg
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* @operator: An (optional) operator, appended after adding the first arg
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* @separator: An (optional) separator, appended after adding the second arg
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*
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* Initialize a dynevent_arg_pair object. A dynevent_arg_pair
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* represents an object used to append argument pairs such as 'type
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* variable_name;' or 'x+y' to the current command string. An
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* argument pair consists of a left-hand-side argument and a
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* right-hand-side argument separated by an operator, which can be
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* whitespace, all followed by a separator, if applicable. After the
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* first arg string is successfully appended to the command string,
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* the optional @operator is appended, followed by the second arg and
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* optional @separator. If no separator was specified when
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* initializing the arg, a space will be appended.
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*/
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void dynevent_arg_pair_init(struct dynevent_arg_pair *arg_pair,
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char operator, char separator)
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{
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memset(arg_pair, '\0', sizeof(*arg_pair));
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if (!operator)
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operator = ' ';
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arg_pair->operator = operator;
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if (!separator)
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separator = ' ';
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arg_pair->separator = separator;
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}
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/**
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* dynevent_create - Create the dynamic event contained in dynevent_cmd
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* @cmd: The dynevent_cmd object containing the dynamic event creation command
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*
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* Once a dynevent_cmd object has been successfully built up via the
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* dynevent_cmd_init(), dynevent_arg_add() and dynevent_arg_pair_add()
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* functions, this function runs the final command to actually create
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* the event.
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*
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* Return: 0 if the event was successfully created, error otherwise.
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*/
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int dynevent_create(struct dynevent_cmd *cmd)
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{
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return cmd->run_command(cmd);
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}
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EXPORT_SYMBOL_GPL(dynevent_create);
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