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![Miroslav Benes](/assets/img/avatar_default.png)
Immediate flag has been used to disable per-task consistency and patch all tasks immediately. It could be useful if the patch doesn't change any function or data semantics. However, it causes problems on its own. The consistency problem is currently broken with respect to immediate patches. func a patches 1i 2i 3 When the patch 3 is applied, only 2i function is checked (by stack checking facility). There might be a task sleeping in 1i though. Such task is migrated to 3, because we do not check 1i in klp_check_stack_func() at all. Coming atomic replace feature would be easier to implement and more reliable without immediate. Thus, remove immediate feature completely and save us from the problems. Note that force feature has the similar problem. However it is considered as a last resort. If used, administrator should not apply any new live patches and should plan for reboot into an updated kernel. The architectures would now need to provide HAVE_RELIABLE_STACKTRACE to fully support livepatch. Signed-off-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
153 lines
3.6 KiB
C
153 lines
3.6 KiB
C
/*
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* Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* livepatch-shadow-fix2.c - Shadow variables, livepatch demo
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*
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* Purpose
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* -------
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*
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* Adds functionality to livepatch-shadow-mod's in-flight data
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* structures through a shadow variable. The livepatch patches a
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* routine that periodically inspects data structures, incrementing a
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* per-data-structure counter, creating the counter if needed.
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*
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*
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* Usage
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* -----
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*
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* This module is not intended to be standalone. See the "Usage"
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* section of livepatch-shadow-mod.c.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/livepatch.h>
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#include <linux/slab.h>
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/* Shadow variable enums */
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#define SV_LEAK 1
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#define SV_COUNTER 2
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struct dummy {
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struct list_head list;
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unsigned long jiffies_expire;
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};
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bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
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{
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int *shadow_count;
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int count;
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/*
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* Patch: handle in-flight dummy structures, if they do not
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* already have a SV_COUNTER shadow variable, then attach a
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* new one.
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*/
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count = 0;
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shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
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&count, sizeof(count),
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GFP_NOWAIT);
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if (shadow_count)
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*shadow_count += 1;
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return time_after(jiffies, d->jiffies_expire);
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}
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void livepatch_fix2_dummy_free(struct dummy *d)
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{
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void **shadow_leak, *leak;
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int *shadow_count;
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/* Patch: copy the memory leak patch from the fix1 module. */
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shadow_leak = klp_shadow_get(d, SV_LEAK);
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if (shadow_leak) {
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leak = *shadow_leak;
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klp_shadow_free(d, SV_LEAK);
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kfree(leak);
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pr_info("%s: dummy @ %p, prevented leak @ %p\n",
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__func__, d, leak);
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} else {
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pr_info("%s: dummy @ %p leaked!\n", __func__, d);
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}
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/*
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* Patch: fetch the SV_COUNTER shadow variable and display
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* the final count. Detach the shadow variable.
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*/
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shadow_count = klp_shadow_get(d, SV_COUNTER);
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if (shadow_count) {
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pr_info("%s: dummy @ %p, check counter = %d\n",
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__func__, d, *shadow_count);
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klp_shadow_free(d, SV_COUNTER);
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}
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kfree(d);
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}
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static struct klp_func funcs[] = {
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{
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.old_name = "dummy_check",
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.new_func = livepatch_fix2_dummy_check,
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},
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{
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.old_name = "dummy_free",
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.new_func = livepatch_fix2_dummy_free,
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}, { }
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};
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static struct klp_object objs[] = {
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{
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.name = "livepatch_shadow_mod",
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.funcs = funcs,
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}, { }
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};
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static struct klp_patch patch = {
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.mod = THIS_MODULE,
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.objs = objs,
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};
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static int livepatch_shadow_fix2_init(void)
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{
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int ret;
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ret = klp_register_patch(&patch);
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if (ret)
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return ret;
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ret = klp_enable_patch(&patch);
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if (ret) {
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WARN_ON(klp_unregister_patch(&patch));
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return ret;
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}
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return 0;
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}
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static void livepatch_shadow_fix2_exit(void)
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{
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/* Cleanup any existing SV_COUNTER shadow variables */
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klp_shadow_free_all(SV_COUNTER);
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WARN_ON(klp_unregister_patch(&patch));
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}
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module_init(livepatch_shadow_fix2_init);
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module_exit(livepatch_shadow_fix2_exit);
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MODULE_LICENSE("GPL");
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MODULE_INFO(livepatch, "Y");
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