// 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");