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-rw-r--r--samples/Kconfig5
-rw-r--r--samples/livepatch/Makefile3
-rw-r--r--samples/livepatch/livepatch-shadow-fix1.c173
-rw-r--r--samples/livepatch/livepatch-shadow-fix2.c168
-rw-r--r--samples/livepatch/livepatch-shadow-mod.c224
5 files changed, 570 insertions, 3 deletions
diff --git a/samples/Kconfig b/samples/Kconfig
index 9cb63188d3ef..c332a3b9de05 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -71,11 +71,10 @@ config SAMPLE_RPMSG_CLIENT
71 the rpmsg bus. 71 the rpmsg bus.
72 72
73config SAMPLE_LIVEPATCH 73config SAMPLE_LIVEPATCH
74 tristate "Build live patching sample -- loadable modules only" 74 tristate "Build live patching samples -- loadable modules only"
75 depends on LIVEPATCH && m 75 depends on LIVEPATCH && m
76 help 76 help
77 Builds a sample live patch that replaces the procfs handler 77 Build sample live patch demonstrations.
78 for /proc/cmdline to print "this has been live patched".
79 78
80config SAMPLE_CONFIGFS 79config SAMPLE_CONFIGFS
81 tristate "Build configfs patching sample -- loadable modules only" 80 tristate "Build configfs patching sample -- loadable modules only"
diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile
index 10319d7ea0b1..539e81d433cd 100644
--- a/samples/livepatch/Makefile
+++ b/samples/livepatch/Makefile
@@ -1 +1,4 @@
1obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-sample.o 1obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-sample.o
2obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-mod.o
3obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix1.o
4obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o
diff --git a/samples/livepatch/livepatch-shadow-fix1.c b/samples/livepatch/livepatch-shadow-fix1.c
new file mode 100644
index 000000000000..fbe0a1f3d99b
--- /dev/null
+++ b/samples/livepatch/livepatch-shadow-fix1.c
@@ -0,0 +1,173 @@
1/*
2 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18/*
19 * livepatch-shadow-fix1.c - Shadow variables, livepatch demo
20 *
21 * Purpose
22 * -------
23 *
24 * Fixes the memory leak introduced in livepatch-shadow-mod through the
25 * use of a shadow variable. This fix demonstrates the "extending" of
26 * short-lived data structures by patching its allocation and release
27 * functions.
28 *
29 *
30 * Usage
31 * -----
32 *
33 * This module is not intended to be standalone. See the "Usage"
34 * section of livepatch-shadow-mod.c.
35 */
36
37#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
38
39#include <linux/module.h>
40#include <linux/kernel.h>
41#include <linux/livepatch.h>
42#include <linux/slab.h>
43
44/* Shadow variable enums */
45#define SV_LEAK 1
46
47/* Allocate new dummies every second */
48#define ALLOC_PERIOD 1
49/* Check for expired dummies after a few new ones have been allocated */
50#define CLEANUP_PERIOD (3 * ALLOC_PERIOD)
51/* Dummies expire after a few cleanup instances */
52#define EXPIRE_PERIOD (4 * CLEANUP_PERIOD)
53
54struct dummy {
55 struct list_head list;
56 unsigned long jiffies_expire;
57};
58
59struct dummy *livepatch_fix1_dummy_alloc(void)
60{
61 struct dummy *d;
62 void *leak;
63
64 d = kzalloc(sizeof(*d), GFP_KERNEL);
65 if (!d)
66 return NULL;
67
68 d->jiffies_expire = jiffies +
69 msecs_to_jiffies(1000 * EXPIRE_PERIOD);
70
71 /*
72 * Patch: save the extra memory location into a SV_LEAK shadow
73 * variable. A patched dummy_free routine can later fetch this
74 * pointer to handle resource release.
75 */
76 leak = kzalloc(sizeof(int), GFP_KERNEL);
77 klp_shadow_alloc(d, SV_LEAK, &leak, sizeof(leak), GFP_KERNEL);
78
79 pr_info("%s: dummy @ %p, expires @ %lx\n",
80 __func__, d, d->jiffies_expire);
81
82 return d;
83}
84
85void livepatch_fix1_dummy_free(struct dummy *d)
86{
87 void **shadow_leak, *leak;
88
89 /*
90 * Patch: fetch the saved SV_LEAK shadow variable, detach and
91 * free it. Note: handle cases where this shadow variable does
92 * not exist (ie, dummy structures allocated before this livepatch
93 * was loaded.)
94 */
95 shadow_leak = klp_shadow_get(d, SV_LEAK);
96 if (shadow_leak) {
97 leak = *shadow_leak;
98 klp_shadow_free(d, SV_LEAK);
99 kfree(leak);
100 pr_info("%s: dummy @ %p, prevented leak @ %p\n",
101 __func__, d, leak);
102 } else {
103 pr_info("%s: dummy @ %p leaked!\n", __func__, d);
104 }
105
106 kfree(d);
107}
108
109static struct klp_func funcs[] = {
110 {
111 .old_name = "dummy_alloc",
112 .new_func = livepatch_fix1_dummy_alloc,
113 },
114 {
115 .old_name = "dummy_free",
116 .new_func = livepatch_fix1_dummy_free,
117 }, { }
118};
119
120static struct klp_object objs[] = {
121 {
122 .name = "livepatch_shadow_mod",
123 .funcs = funcs,
124 }, { }
125};
126
127static struct klp_patch patch = {
128 .mod = THIS_MODULE,
129 .objs = objs,
130};
131
132static int livepatch_shadow_fix1_init(void)
133{
134 int ret;
135
136 if (!klp_have_reliable_stack() && !patch.immediate) {
137 /*
138 * WARNING: Be very careful when using 'patch.immediate' in
139 * your patches. It's ok to use it for simple patches like
140 * this, but for more complex patches which change function
141 * semantics, locking semantics, or data structures, it may not
142 * be safe. Use of this option will also prevent removal of
143 * the patch.
144 *
145 * See Documentation/livepatch/livepatch.txt for more details.
146 */
147 patch.immediate = true;
148 pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n");
149 }
150
151 ret = klp_register_patch(&patch);
152 if (ret)
153 return ret;
154 ret = klp_enable_patch(&patch);
155 if (ret) {
156 WARN_ON(klp_unregister_patch(&patch));
157 return ret;
158 }
159 return 0;
160}
161
162static void livepatch_shadow_fix1_exit(void)
163{
164 /* Cleanup any existing SV_LEAK shadow variables */
165 klp_shadow_free_all(SV_LEAK);
166
167 WARN_ON(klp_unregister_patch(&patch));
168}
169
170module_init(livepatch_shadow_fix1_init);
171module_exit(livepatch_shadow_fix1_exit);
172MODULE_LICENSE("GPL");
173MODULE_INFO(livepatch, "Y");
diff --git a/samples/livepatch/livepatch-shadow-fix2.c b/samples/livepatch/livepatch-shadow-fix2.c
new file mode 100644
index 000000000000..53c1794bdc5f
--- /dev/null
+++ b/samples/livepatch/livepatch-shadow-fix2.c
@@ -0,0 +1,168 @@
1/*
2 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18/*
19 * livepatch-shadow-fix2.c - Shadow variables, livepatch demo
20 *
21 * Purpose
22 * -------
23 *
24 * Adds functionality to livepatch-shadow-mod's in-flight data
25 * structures through a shadow variable. The livepatch patches a
26 * routine that periodically inspects data structures, incrementing a
27 * per-data-structure counter, creating the counter if needed.
28 *
29 *
30 * Usage
31 * -----
32 *
33 * This module is not intended to be standalone. See the "Usage"
34 * section of livepatch-shadow-mod.c.
35 */
36
37#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
38
39#include <linux/module.h>
40#include <linux/kernel.h>
41#include <linux/livepatch.h>
42#include <linux/slab.h>
43
44/* Shadow variable enums */
45#define SV_LEAK 1
46#define SV_COUNTER 2
47
48struct dummy {
49 struct list_head list;
50 unsigned long jiffies_expire;
51};
52
53bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
54{
55 int *shadow_count;
56 int count;
57
58 /*
59 * Patch: handle in-flight dummy structures, if they do not
60 * already have a SV_COUNTER shadow variable, then attach a
61 * new one.
62 */
63 count = 0;
64 shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
65 &count, sizeof(count),
66 GFP_NOWAIT);
67 if (shadow_count)
68 *shadow_count += 1;
69
70 return time_after(jiffies, d->jiffies_expire);
71}
72
73void livepatch_fix2_dummy_free(struct dummy *d)
74{
75 void **shadow_leak, *leak;
76 int *shadow_count;
77
78 /* Patch: copy the memory leak patch from the fix1 module. */
79 shadow_leak = klp_shadow_get(d, SV_LEAK);
80 if (shadow_leak) {
81 leak = *shadow_leak;
82 klp_shadow_free(d, SV_LEAK);
83 kfree(leak);
84 pr_info("%s: dummy @ %p, prevented leak @ %p\n",
85 __func__, d, leak);
86 } else {
87 pr_info("%s: dummy @ %p leaked!\n", __func__, d);
88 }
89
90 /*
91 * Patch: fetch the SV_COUNTER shadow variable and display
92 * the final count. Detach the shadow variable.
93 */
94 shadow_count = klp_shadow_get(d, SV_COUNTER);
95 if (shadow_count) {
96 pr_info("%s: dummy @ %p, check counter = %d\n",
97 __func__, d, *shadow_count);
98 klp_shadow_free(d, SV_COUNTER);
99 }
100
101 kfree(d);
102}
103
104static struct klp_func funcs[] = {
105 {
106 .old_name = "dummy_check",
107 .new_func = livepatch_fix2_dummy_check,
108 },
109 {
110 .old_name = "dummy_free",
111 .new_func = livepatch_fix2_dummy_free,
112 }, { }
113};
114
115static struct klp_object objs[] = {
116 {
117 .name = "livepatch_shadow_mod",
118 .funcs = funcs,
119 }, { }
120};
121
122static struct klp_patch patch = {
123 .mod = THIS_MODULE,
124 .objs = objs,
125};
126
127static int livepatch_shadow_fix2_init(void)
128{
129 int ret;
130
131 if (!klp_have_reliable_stack() && !patch.immediate) {
132 /*
133 * WARNING: Be very careful when using 'patch.immediate' in
134 * your patches. It's ok to use it for simple patches like
135 * this, but for more complex patches which change function
136 * semantics, locking semantics, or data structures, it may not
137 * be safe. Use of this option will also prevent removal of
138 * the patch.
139 *
140 * See Documentation/livepatch/livepatch.txt for more details.
141 */
142 patch.immediate = true;
143 pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n");
144 }
145
146 ret = klp_register_patch(&patch);
147 if (ret)
148 return ret;
149 ret = klp_enable_patch(&patch);
150 if (ret) {
151 WARN_ON(klp_unregister_patch(&patch));
152 return ret;
153 }
154 return 0;
155}
156
157static void livepatch_shadow_fix2_exit(void)
158{
159 /* Cleanup any existing SV_COUNTER shadow variables */
160 klp_shadow_free_all(SV_COUNTER);
161
162 WARN_ON(klp_unregister_patch(&patch));
163}
164
165module_init(livepatch_shadow_fix2_init);
166module_exit(livepatch_shadow_fix2_exit);
167MODULE_LICENSE("GPL");
168MODULE_INFO(livepatch, "Y");
diff --git a/samples/livepatch/livepatch-shadow-mod.c b/samples/livepatch/livepatch-shadow-mod.c
new file mode 100644
index 000000000000..4c54b250332d
--- /dev/null
+++ b/samples/livepatch/livepatch-shadow-mod.c
@@ -0,0 +1,224 @@
1/*
2 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18/*
19 * livepatch-shadow-mod.c - Shadow variables, buggy module demo
20 *
21 * Purpose
22 * -------
23 *
24 * As a demonstration of livepatch shadow variable API, this module
25 * introduces memory leak behavior that livepatch modules
26 * livepatch-shadow-fix1.ko and livepatch-shadow-fix2.ko correct and
27 * enhance.
28 *
29 * WARNING - even though the livepatch-shadow-fix modules patch the
30 * memory leak, please load these modules at your own risk -- some
31 * amount of memory may leaked before the bug is patched.
32 *
33 *
34 * Usage
35 * -----
36 *
37 * Step 1 - Load the buggy demonstration module:
38 *
39 * insmod samples/livepatch/livepatch-shadow-mod.ko
40 *
41 * Watch dmesg output for a few moments to see new dummy being allocated
42 * and a periodic cleanup check. (Note: a small amount of memory is
43 * being leaked.)
44 *
45 *
46 * Step 2 - Load livepatch fix1:
47 *
48 * insmod samples/livepatch/livepatch-shadow-fix1.ko
49 *
50 * Continue watching dmesg and note that now livepatch_fix1_dummy_free()
51 * and livepatch_fix1_dummy_alloc() are logging messages about leaked
52 * memory and eventually leaks prevented.
53 *
54 *
55 * Step 3 - Load livepatch fix2 (on top of fix1):
56 *
57 * insmod samples/livepatch/livepatch-shadow-fix2.ko
58 *
59 * This module extends functionality through shadow variables, as a new
60 * "check" counter is added to the dummy structure. Periodic dmesg
61 * messages will log these as dummies are cleaned up.
62 *
63 *
64 * Step 4 - Cleanup
65 *
66 * Unwind the demonstration by disabling the livepatch fix modules, then
67 * removing them and the demo module:
68 *
69 * echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix2/enabled
70 * echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix1/enabled
71 * rmmod livepatch-shadow-fix2
72 * rmmod livepatch-shadow-fix1
73 * rmmod livepatch-shadow-mod
74 */
75
76
77#include <linux/kernel.h>
78#include <linux/module.h>
79#include <linux/sched.h>
80#include <linux/slab.h>
81#include <linux/stat.h>
82#include <linux/workqueue.h>
83
84MODULE_LICENSE("GPL");
85MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
86MODULE_DESCRIPTION("Buggy module for shadow variable demo");
87
88/* Allocate new dummies every second */
89#define ALLOC_PERIOD 1
90/* Check for expired dummies after a few new ones have been allocated */
91#define CLEANUP_PERIOD (3 * ALLOC_PERIOD)
92/* Dummies expire after a few cleanup instances */
93#define EXPIRE_PERIOD (4 * CLEANUP_PERIOD)
94
95/*
96 * Keep a list of all the dummies so we can clean up any residual ones
97 * on module exit
98 */
99LIST_HEAD(dummy_list);
100DEFINE_MUTEX(dummy_list_mutex);
101
102struct dummy {
103 struct list_head list;
104 unsigned long jiffies_expire;
105};
106
107noinline struct dummy *dummy_alloc(void)
108{
109 struct dummy *d;
110 void *leak;
111
112 d = kzalloc(sizeof(*d), GFP_KERNEL);
113 if (!d)
114 return NULL;
115
116 d->jiffies_expire = jiffies +
117 msecs_to_jiffies(1000 * EXPIRE_PERIOD);
118
119 /* Oops, forgot to save leak! */
120 leak = kzalloc(sizeof(int), GFP_KERNEL);
121
122 pr_info("%s: dummy @ %p, expires @ %lx\n",
123 __func__, d, d->jiffies_expire);
124
125 return d;
126}
127
128noinline void dummy_free(struct dummy *d)
129{
130 pr_info("%s: dummy @ %p, expired = %lx\n",
131 __func__, d, d->jiffies_expire);
132
133 kfree(d);
134}
135
136noinline bool dummy_check(struct dummy *d, unsigned long jiffies)
137{
138 return time_after(jiffies, d->jiffies_expire);
139}
140
141/*
142 * alloc_work_func: allocates new dummy structures, allocates additional
143 * memory, aptly named "leak", but doesn't keep
144 * permanent record of it.
145 */
146
147static void alloc_work_func(struct work_struct *work);
148static DECLARE_DELAYED_WORK(alloc_dwork, alloc_work_func);
149
150static void alloc_work_func(struct work_struct *work)
151{
152 struct dummy *d;
153
154 d = dummy_alloc();
155 if (!d)
156 return;
157
158 mutex_lock(&dummy_list_mutex);
159 list_add(&d->list, &dummy_list);
160 mutex_unlock(&dummy_list_mutex);
161
162 schedule_delayed_work(&alloc_dwork,
163 msecs_to_jiffies(1000 * ALLOC_PERIOD));
164}
165
166/*
167 * cleanup_work_func: frees dummy structures. Without knownledge of
168 * "leak", it leaks the additional memory that
169 * alloc_work_func created.
170 */
171
172static void cleanup_work_func(struct work_struct *work);
173static DECLARE_DELAYED_WORK(cleanup_dwork, cleanup_work_func);
174
175static void cleanup_work_func(struct work_struct *work)
176{
177 struct dummy *d, *tmp;
178 unsigned long j;
179
180 j = jiffies;
181 pr_info("%s: jiffies = %lx\n", __func__, j);
182
183 mutex_lock(&dummy_list_mutex);
184 list_for_each_entry_safe(d, tmp, &dummy_list, list) {
185
186 /* Kick out and free any expired dummies */
187 if (dummy_check(d, j)) {
188 list_del(&d->list);
189 dummy_free(d);
190 }
191 }
192 mutex_unlock(&dummy_list_mutex);
193
194 schedule_delayed_work(&cleanup_dwork,
195 msecs_to_jiffies(1000 * CLEANUP_PERIOD));
196}
197
198static int livepatch_shadow_mod_init(void)
199{
200 schedule_delayed_work(&alloc_dwork,
201 msecs_to_jiffies(1000 * ALLOC_PERIOD));
202 schedule_delayed_work(&cleanup_dwork,
203 msecs_to_jiffies(1000 * CLEANUP_PERIOD));
204
205 return 0;
206}
207
208static void livepatch_shadow_mod_exit(void)
209{
210 struct dummy *d, *tmp;
211
212 /* Wait for any dummies at work */
213 cancel_delayed_work_sync(&alloc_dwork);
214 cancel_delayed_work_sync(&cleanup_dwork);
215
216 /* Cleanup residual dummies */
217 list_for_each_entry_safe(d, tmp, &dummy_list, list) {
218 list_del(&d->list);
219 dummy_free(d);
220 }
221}
222
223module_init(livepatch_shadow_mod_init);
224module_exit(livepatch_shadow_mod_exit);
generated by cgit v1.2.2 (git 2.25.0) at 2026-01-07 17:53:19 -0500