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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174// 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){ int **shadow_leak = shadow_data; int **leak = ctor_data;
if (!ctor_data) return -EINVAL;
*shadow_leak = *leak; return 0;}
static struct dummy *livepatch_fix1_dummy_alloc(void){ struct dummy *d; int *leak; int **shadow_leak;
d = kzalloc(sizeof(*d), GFP_KERNEL); if (!d) return NULL;
d->jiffies_expire = jiffies + secs_to_jiffies(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(*leak), GFP_KERNEL); if (!leak) goto err_leak;
shadow_leak = klp_shadow_alloc(d, SV_LEAK, sizeof(leak), GFP_KERNEL, shadow_leak_ctor, &leak); if (!shadow_leak) { pr_err("%s: failed to allocate shadow variable for the leaking pointer: dummy @ %p, leak @ %p\n", __func__, d, leak); goto err_shadow; }
pr_info("%s: dummy @ %p, expires @ %lx\n", __func__, d, d->jiffies_expire);
return d;
err_shadow: kfree(leak);err_leak: kfree(d); return NULL;}
static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data){ void *d = obj; int **shadow_leak = shadow_data;
pr_info("%s: dummy @ %p, prevented leak @ %p\n", __func__, d, *shadow_leak); kfree(*shadow_leak);}
static void livepatch_fix1_dummy_free(struct dummy *d){ int **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_DESCRIPTION("Live patching demo for shadow variables");MODULE_LICENSE("GPL");MODULE_INFO(livepatch, "Y");