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| 3 | * Copyright (C) 2017 Joe Lawrence <[email protected]>
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| 4 |
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| 5 |
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| 6 | |
| 7 | * livepatch-shadow-fix2.c - Shadow variables, livepatch demo
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| 8 | *
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| 9 | * Purpose
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| 10 | * -------
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| 11 | *
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| 12 | * Adds functionality to livepatch-shadow-mod's in-flight data
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| 13 | * structures through a shadow variable. The livepatch patches a
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| 14 | * routine that periodically inspects data structures, incrementing a
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| 15 | * per-data-structure counter, creating the counter if needed.
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| 16 | *
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| 17 | *
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| 18 | * Usage
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| 19 | * -----
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| 20 | *
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| 21 | * This module is not intended to be standalone. See the "Usage"
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| 22 | * section of livepatch-shadow-mod.c.
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| 23 |
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| 24 |
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| 25 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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| 26 |
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| 27 | #include <linux/module.h>
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| 28 | #include <linux/kernel.h>
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| 29 | #include <linux/livepatch.h>
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| 30 | #include <linux/slab.h>
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| 31 |
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| 32 |
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| 33 | #define SV_LEAK 1
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| 34 | #define SV_COUNTER 2
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| 35 |
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| 36 | struct dummy {
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| 37 | struct list_head list;
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| 38 | unsigned long jiffies_expire;
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| 39 | };
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| 40 |
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| 41 | static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
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| 42 | {
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| 43 | int *shadow_count;
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| 44 |
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| 45 | |
| 46 | * Patch: handle in-flight dummy structures, if they do not
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| 47 | * already have a SV_COUNTER shadow variable, then attach a
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| 48 | * new one.
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| 49 |
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| 50 | shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
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| 51 | sizeof(*shadow_count), GFP_NOWAIT,
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| 52 | NULL, NULL);
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| 53 | if (shadow_count)
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| 54 | *shadow_count += 1;
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| 55 |
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| 56 | return time_after(jiffies, d->jiffies_expire);
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| 57 | }
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| 58 |
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| 59 | static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
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| 60 | {
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| 61 | void *d = obj;
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| 62 | int **shadow_leak = shadow_data;
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| 63 |
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| 64 | pr_info("%s: dummy @ %p, prevented leak @ %p\n",
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| 65 | __func__, d, *shadow_leak);
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| 66 | kfree(*shadow_leak);
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| 67 | }
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| 68 |
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| 69 | static void livepatch_fix2_dummy_free(struct dummy *d)
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| 70 | {
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| 71 | int **shadow_leak;
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| 72 | int *shadow_count;
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| 73 |
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| 74 |
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| 75 | shadow_leak = klp_shadow_get(d, SV_LEAK);
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| 76 | if (shadow_leak)
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| 77 | klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
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| 78 | else
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| 79 | pr_info("%s: dummy @ %p leaked!\n", __func__, d);
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| 80 |
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| 81 | |
| 82 | * Patch: fetch the SV_COUNTER shadow variable and display
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| 83 | * the final count. Detach the shadow variable.
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| 84 |
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| 85 | shadow_count = klp_shadow_get(d, SV_COUNTER);
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| 86 | if (shadow_count) {
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| 87 | pr_info("%s: dummy @ %p, check counter = %d\n",
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| 88 | __func__, d, *shadow_count);
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| 89 | klp_shadow_free(d, SV_COUNTER, NULL);
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| 90 | }
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| 91 |
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| 92 | kfree(d);
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| 93 | }
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| 94 |
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| 95 | static struct klp_func funcs[] = {
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| 96 | {
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| 97 | .old_name = "dummy_check",
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| 98 | .new_func = livepatch_fix2_dummy_check,
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| 99 | },
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| 100 | {
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| 101 | .old_name = "dummy_free",
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| 102 | .new_func = livepatch_fix2_dummy_free,
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| 103 | }, { }
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| 104 | };
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| 105 |
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| 106 | static struct klp_object objs[] = {
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| 107 | {
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| 108 | .name = "livepatch_shadow_mod",
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| 109 | .funcs = funcs,
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| 110 | }, { }
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| 111 | };
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| 112 |
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| 113 | static struct klp_patch patch = {
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| 114 | .mod = THIS_MODULE,
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| 115 | .objs = objs,
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| 116 | };
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| 117 |
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| 118 | static int livepatch_shadow_fix2_init(void)
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| 119 | {
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| 120 | return klp_enable_patch(&patch);
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| 121 | }
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| 122 |
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| 123 | static void livepatch_shadow_fix2_exit(void)
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| 124 | {
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| 125 |
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| 126 | klp_shadow_free_all(SV_COUNTER, NULL);
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| 127 | }
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| 128 |
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| 129 | module_init(livepatch_shadow_fix2_init);
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| 130 | module_exit(livepatch_shadow_fix2_exit);
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| 131 | MODULE_LICENSE("GPL");
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| 132 | MODULE_INFO(livepatch, "Y");
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