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![Steven Rostedt (VMware)](/assets/img/avatar_default.png)
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>
364 lines
7.6 KiB
C
364 lines
7.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Infrastructure for statistic tracing (histogram output).
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*
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* Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
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*
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* Based on the code from trace_branch.c which is
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* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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*
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*/
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#include <linux/security.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/rbtree.h>
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#include <linux/tracefs.h>
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#include "trace_stat.h"
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#include "trace.h"
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/*
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* List of stat red-black nodes from a tracer
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* We use a such tree to sort quickly the stat
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* entries from the tracer.
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*/
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struct stat_node {
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struct rb_node node;
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void *stat;
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};
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/* A stat session is the stats output in one file */
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struct stat_session {
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struct list_head session_list;
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struct tracer_stat *ts;
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struct rb_root stat_root;
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struct mutex stat_mutex;
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struct dentry *file;
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};
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/* All of the sessions currently in use. Each stat file embed one session */
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static LIST_HEAD(all_stat_sessions);
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static DEFINE_MUTEX(all_stat_sessions_mutex);
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/* The root directory for all stat files */
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static struct dentry *stat_dir;
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static void __reset_stat_session(struct stat_session *session)
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{
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struct stat_node *snode, *n;
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rbtree_postorder_for_each_entry_safe(snode, n, &session->stat_root, node) {
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if (session->ts->stat_release)
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session->ts->stat_release(snode->stat);
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kfree(snode);
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}
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session->stat_root = RB_ROOT;
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}
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static void reset_stat_session(struct stat_session *session)
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{
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mutex_lock(&session->stat_mutex);
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__reset_stat_session(session);
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mutex_unlock(&session->stat_mutex);
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}
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static void destroy_session(struct stat_session *session)
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{
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tracefs_remove(session->file);
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__reset_stat_session(session);
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mutex_destroy(&session->stat_mutex);
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kfree(session);
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}
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static int insert_stat(struct rb_root *root, void *stat, cmp_func_t cmp)
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{
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struct rb_node **new = &(root->rb_node), *parent = NULL;
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struct stat_node *data;
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data = kzalloc(sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->stat = stat;
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/*
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* Figure out where to put new node
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* This is a descendent sorting
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*/
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while (*new) {
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struct stat_node *this;
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int result;
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this = container_of(*new, struct stat_node, node);
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result = cmp(data->stat, this->stat);
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parent = *new;
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if (result >= 0)
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new = &((*new)->rb_left);
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else
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new = &((*new)->rb_right);
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}
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rb_link_node(&data->node, parent, new);
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rb_insert_color(&data->node, root);
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return 0;
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}
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/*
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* For tracers that don't provide a stat_cmp callback.
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* This one will force an insertion as right-most node
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* in the rbtree.
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*/
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static int dummy_cmp(const void *p1, const void *p2)
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{
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return -1;
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}
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/*
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* Initialize the stat rbtree at each trace_stat file opening.
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* All of these copies and sorting are required on all opening
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* since the stats could have changed between two file sessions.
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*/
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static int stat_seq_init(struct stat_session *session)
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{
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struct tracer_stat *ts = session->ts;
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struct rb_root *root = &session->stat_root;
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void *stat;
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int ret = 0;
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int i;
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mutex_lock(&session->stat_mutex);
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__reset_stat_session(session);
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if (!ts->stat_cmp)
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ts->stat_cmp = dummy_cmp;
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stat = ts->stat_start(ts);
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if (!stat)
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goto exit;
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ret = insert_stat(root, stat, ts->stat_cmp);
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if (ret)
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goto exit;
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/*
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* Iterate over the tracer stat entries and store them in an rbtree.
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*/
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for (i = 1; ; i++) {
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stat = ts->stat_next(stat, i);
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/* End of insertion */
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if (!stat)
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break;
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ret = insert_stat(root, stat, ts->stat_cmp);
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if (ret)
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goto exit_free_rbtree;
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}
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exit:
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mutex_unlock(&session->stat_mutex);
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return ret;
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exit_free_rbtree:
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__reset_stat_session(session);
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mutex_unlock(&session->stat_mutex);
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return ret;
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}
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static void *stat_seq_start(struct seq_file *s, loff_t *pos)
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{
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struct stat_session *session = s->private;
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struct rb_node *node;
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int n = *pos;
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int i;
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/* Prevent from tracer switch or rbtree modification */
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mutex_lock(&session->stat_mutex);
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/* If we are in the beginning of the file, print the headers */
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if (session->ts->stat_headers) {
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if (n == 0)
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return SEQ_START_TOKEN;
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n--;
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}
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node = rb_first(&session->stat_root);
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for (i = 0; node && i < n; i++)
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node = rb_next(node);
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return node;
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}
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static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
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{
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struct stat_session *session = s->private;
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struct rb_node *node = p;
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(*pos)++;
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if (p == SEQ_START_TOKEN)
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return rb_first(&session->stat_root);
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return rb_next(node);
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}
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static void stat_seq_stop(struct seq_file *s, void *p)
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{
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struct stat_session *session = s->private;
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mutex_unlock(&session->stat_mutex);
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}
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static int stat_seq_show(struct seq_file *s, void *v)
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{
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struct stat_session *session = s->private;
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struct stat_node *l = container_of(v, struct stat_node, node);
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if (v == SEQ_START_TOKEN)
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return session->ts->stat_headers(s);
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return session->ts->stat_show(s, l->stat);
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}
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static const struct seq_operations trace_stat_seq_ops = {
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.start = stat_seq_start,
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.next = stat_seq_next,
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.stop = stat_seq_stop,
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.show = stat_seq_show
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};
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/* The session stat is refilled and resorted at each stat file opening */
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static int tracing_stat_open(struct inode *inode, struct file *file)
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{
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int ret;
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struct seq_file *m;
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struct stat_session *session = inode->i_private;
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ret = security_locked_down(LOCKDOWN_TRACEFS);
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if (ret)
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return ret;
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ret = stat_seq_init(session);
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if (ret)
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return ret;
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ret = seq_open(file, &trace_stat_seq_ops);
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if (ret) {
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reset_stat_session(session);
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return ret;
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}
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m = file->private_data;
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m->private = session;
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return ret;
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}
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/*
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* Avoid consuming memory with our now useless rbtree.
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*/
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static int tracing_stat_release(struct inode *i, struct file *f)
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{
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struct stat_session *session = i->i_private;
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reset_stat_session(session);
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return seq_release(i, f);
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}
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static const struct file_operations tracing_stat_fops = {
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.open = tracing_stat_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = tracing_stat_release
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};
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static int tracing_stat_init(void)
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{
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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 -ENODEV;
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stat_dir = tracefs_create_dir("trace_stat", NULL);
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if (!stat_dir) {
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pr_warn("Could not create tracefs 'trace_stat' entry\n");
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return -ENOMEM;
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}
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return 0;
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}
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static int init_stat_file(struct stat_session *session)
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{
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int ret;
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if (!stat_dir && (ret = tracing_stat_init()))
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return ret;
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session->file = tracefs_create_file(session->ts->name, TRACE_MODE_WRITE,
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stat_dir, session,
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&tracing_stat_fops);
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if (!session->file)
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return -ENOMEM;
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return 0;
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}
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int register_stat_tracer(struct tracer_stat *trace)
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{
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struct stat_session *session, *node;
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int ret = -EINVAL;
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if (!trace)
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return -EINVAL;
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if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
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return -EINVAL;
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/* Already registered? */
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mutex_lock(&all_stat_sessions_mutex);
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list_for_each_entry(node, &all_stat_sessions, session_list) {
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if (node->ts == trace)
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goto out;
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}
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ret = -ENOMEM;
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/* Init the session */
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session = kzalloc(sizeof(*session), GFP_KERNEL);
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if (!session)
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goto out;
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session->ts = trace;
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INIT_LIST_HEAD(&session->session_list);
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mutex_init(&session->stat_mutex);
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ret = init_stat_file(session);
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if (ret) {
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destroy_session(session);
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goto out;
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}
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ret = 0;
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/* Register */
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list_add_tail(&session->session_list, &all_stat_sessions);
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out:
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mutex_unlock(&all_stat_sessions_mutex);
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return ret;
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}
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void unregister_stat_tracer(struct tracer_stat *trace)
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{
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struct stat_session *node, *tmp;
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mutex_lock(&all_stat_sessions_mutex);
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list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
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if (node->ts == trace) {
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list_del(&node->session_list);
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destroy_session(node);
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break;
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}
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}
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mutex_unlock(&all_stat_sessions_mutex);
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}
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