linux/samples/livepatch/livepatch-shadow-fix1.c
Thomas Gleixner 1ccea77e2a treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13
Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version this program is distributed in the
  hope that it will be useful but without any warranty without even
  the implied warranty of merchantability or fitness for a particular
  purpose see the gnu general public license for more details you
  should have received a copy of the gnu general public license along
  with this program if not see http www gnu org licenses

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version this program is distributed in the
  hope that it will be useful but without any warranty without even
  the implied warranty of merchantability or fitness for a particular
  purpose see the gnu general public license for more details [based]
  [from] [clk] [highbank] [c] you should have received a copy of the
  gnu general public license along with this program if not see http
  www gnu org licenses

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 355 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190519154041.837383322@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-21 11:28:45 +02:00

161 lines
3.6 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
*/
/*
* livepatch-shadow-fix1.c - Shadow variables, livepatch demo
*
* Purpose
* -------
*
* Fixes the memory leak introduced in livepatch-shadow-mod through the
* use of a shadow variable. This fix demonstrates the "extending" of
* short-lived data structures by patching its allocation and release
* functions.
*
*
* Usage
* -----
*
* This module is not intended to be standalone. See the "Usage"
* section of livepatch-shadow-mod.c.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/livepatch.h>
#include <linux/slab.h>
/* Shadow variable enums */
#define SV_LEAK 1
/* Allocate new dummies every second */
#define ALLOC_PERIOD 1
/* Check for expired dummies after a few new ones have been allocated */
#define CLEANUP_PERIOD (3 * ALLOC_PERIOD)
/* Dummies expire after a few cleanup instances */
#define EXPIRE_PERIOD (4 * CLEANUP_PERIOD)
struct dummy {
struct list_head list;
unsigned long jiffies_expire;
};
/*
* The constructor makes more sense together with klp_shadow_get_or_alloc().
* In this example, it would be safe to assign the pointer also to the shadow
* variable returned by klp_shadow_alloc(). But we wanted to show the more
* complicated use of the API.
*/
static int shadow_leak_ctor(void *obj, void *shadow_data, void *ctor_data)
{
void **shadow_leak = shadow_data;
void *leak = ctor_data;
*shadow_leak = leak;
return 0;
}
static struct dummy *livepatch_fix1_dummy_alloc(void)
{
struct dummy *d;
void *leak;
d = kzalloc(sizeof(*d), GFP_KERNEL);
if (!d)
return NULL;
d->jiffies_expire = jiffies +
msecs_to_jiffies(1000 * EXPIRE_PERIOD);
/*
* Patch: save the extra memory location into a SV_LEAK shadow
* variable. A patched dummy_free routine can later fetch this
* pointer to handle resource release.
*/
leak = kzalloc(sizeof(int), GFP_KERNEL);
if (!leak) {
kfree(d);
return NULL;
}
klp_shadow_alloc(d, SV_LEAK, sizeof(leak), GFP_KERNEL,
shadow_leak_ctor, leak);
pr_info("%s: dummy @ %p, expires @ %lx\n",
__func__, d, d->jiffies_expire);
return d;
}
static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data)
{
void *d = obj;
void **shadow_leak = shadow_data;
kfree(*shadow_leak);
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
__func__, d, *shadow_leak);
}
static void livepatch_fix1_dummy_free(struct dummy *d)
{
void **shadow_leak;
/*
* Patch: fetch the saved SV_LEAK shadow variable, detach and
* free it. Note: handle cases where this shadow variable does
* not exist (ie, dummy structures allocated before this livepatch
* was loaded.)
*/
shadow_leak = klp_shadow_get(d, SV_LEAK);
if (shadow_leak)
klp_shadow_free(d, SV_LEAK, livepatch_fix1_dummy_leak_dtor);
else
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
kfree(d);
}
static struct klp_func funcs[] = {
{
.old_name = "dummy_alloc",
.new_func = livepatch_fix1_dummy_alloc,
},
{
.old_name = "dummy_free",
.new_func = livepatch_fix1_dummy_free,
}, { }
};
static struct klp_object objs[] = {
{
.name = "livepatch_shadow_mod",
.funcs = funcs,
}, { }
};
static struct klp_patch patch = {
.mod = THIS_MODULE,
.objs = objs,
};
static int livepatch_shadow_fix1_init(void)
{
return klp_enable_patch(&patch);
}
static void livepatch_shadow_fix1_exit(void)
{
/* Cleanup any existing SV_LEAK shadow variables */
klp_shadow_free_all(SV_LEAK, livepatch_fix1_dummy_leak_dtor);
}
module_init(livepatch_shadow_fix1_init);
module_exit(livepatch_shadow_fix1_exit);
MODULE_LICENSE("GPL");
MODULE_INFO(livepatch, "Y");