From b700e7f03df5d92f85fa5247fe1f557528d3363d Mon Sep 17 00:00:00 2001 From: Seth Jennings Date: Tue, 16 Dec 2014 11:58:19 -0600 Subject: livepatch: kernel: add support for live patching This commit introduces code for the live patching core. It implements an ftrace-based mechanism and kernel interface for doing live patching of kernel and kernel module functions. It represents the greatest common functionality set between kpatch and kgraft and can accept patches built using either method. This first version does not implement any consistency mechanism that ensures that old and new code do not run together. In practice, ~90% of CVEs are safe to apply in this way, since they simply add a conditional check. However, any function change that can not execute safely with the old version of the function can _not_ be safely applied in this version. [ jkosina@suse.cz: due to the number of contributions that got folded into this original patch from Seth Jennings, add SUSE's copyright as well, as discussed via e-mail ] Signed-off-by: Seth Jennings Signed-off-by: Josh Poimboeuf Reviewed-by: Miroslav Benes Reviewed-by: Petr Mladek Reviewed-by: Masami Hiramatsu Signed-off-by: Miroslav Benes Signed-off-by: Petr Mladek Signed-off-by: Jiri Kosina --- include/linux/livepatch.h | 133 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 include/linux/livepatch.h (limited to 'include/linux/livepatch.h') diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h new file mode 100644 index 000000000000..950bc615842f --- /dev/null +++ b/include/linux/livepatch.h @@ -0,0 +1,133 @@ +/* + * livepatch.h - Kernel Live Patching Core + * + * Copyright (C) 2014 Seth Jennings + * Copyright (C) 2014 SUSE + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see . + */ + +#ifndef _LINUX_LIVEPATCH_H_ +#define _LINUX_LIVEPATCH_H_ + +#include +#include + +#if IS_ENABLED(CONFIG_LIVE_PATCHING) + +#include + +enum klp_state { + KLP_DISABLED, + KLP_ENABLED +}; + +/** + * struct klp_func - function structure for live patching + * @old_name: name of the function to be patched + * @new_func: pointer to the patched function code + * @old_addr: a hint conveying at what address the old function + * can be found (optional, vmlinux patches only) + * @kobj: kobject for sysfs resources + * @fops: ftrace operations structure + * @state: tracks function-level patch application state + */ +struct klp_func { + /* external */ + const char *old_name; + void *new_func; + /* + * The old_addr field is optional and can be used to resolve + * duplicate symbol names in the vmlinux object. If this + * information is not present, the symbol is located by name + * with kallsyms. If the name is not unique and old_addr is + * not provided, the patch application fails as there is no + * way to resolve the ambiguity. + */ + unsigned long old_addr; + + /* internal */ + struct kobject kobj; + struct ftrace_ops *fops; + enum klp_state state; +}; + +/** + * struct klp_reloc - relocation structure for live patching + * @loc: address where the relocation will be written + * @val: address of the referenced symbol (optional, + * vmlinux patches only) + * @type: ELF relocation type + * @name: name of the referenced symbol (for lookup/verification) + * @addend: offset from the referenced symbol + * @external: symbol is either exported or within the live patch module itself + */ +struct klp_reloc { + unsigned long loc; + unsigned long val; + unsigned long type; + const char *name; + int addend; + int external; +}; + +/** + * struct klp_object - kernel object structure for live patching + * @name: module name (or NULL for vmlinux) + * @relocs: relocation entries to be applied at load time + * @funcs: function entries for functions to be patched in the object + * @kobj: kobject for sysfs resources + * @mod: kernel module associated with the patched object + * (NULL for vmlinux) + * @state: tracks object-level patch application state + */ +struct klp_object { + /* external */ + const char *name; + struct klp_reloc *relocs; + struct klp_func *funcs; + + /* internal */ + struct kobject *kobj; + struct module *mod; + enum klp_state state; +}; + +/** + * struct klp_patch - patch structure for live patching + * @mod: reference to the live patch module + * @objs: object entries for kernel objects to be patched + * @list: list node for global list of registered patches + * @kobj: kobject for sysfs resources + * @state: tracks patch-level application state + */ +struct klp_patch { + /* external */ + struct module *mod; + struct klp_object *objs; + + /* internal */ + struct list_head list; + struct kobject kobj; + enum klp_state state; +}; + +extern int klp_register_patch(struct klp_patch *); +extern int klp_unregister_patch(struct klp_patch *); +extern int klp_enable_patch(struct klp_patch *); +extern int klp_disable_patch(struct klp_patch *); + +#endif /* CONFIG_LIVE_PATCHING */ + +#endif /* _LINUX_LIVEPATCH_H_ */ -- cgit From 3c33f5b99d688deafd21d4a770303691c7c3a320 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Tue, 20 Jan 2015 09:26:19 -0600 Subject: livepatch: support for repatching a function Add support for patching a function multiple times. If multiple patches affect a function, the function in the most recently enabled patch "wins". This enables a cumulative patch upgrade path, where each patch is a superset of previous patches. This requires restructuring the data a little bit. With the current design, where each klp_func struct has its own ftrace_ops, we'd have to unregister the old ops and then register the new ops, because FTRACE_OPS_FL_IPMODIFY prevents us from having two ops registered for the same function at the same time. That would leave a regression window where the function isn't patched at all (not good for a patch upgrade path). This patch replaces the per-klp_func ftrace_ops with a global klp_ops list, with one ftrace_ops per original function. A single ftrace_ops is shared between all klp_funcs which have the same old_addr. This allows the switch between function versions to happen instantaneously by updating the klp_ops struct's func_stack list. The winner is the klp_func at the top of the func_stack (front of the list). [ jkosina@suse.cz: turn WARN_ON() into WARN_ON_ONCE() in ftrace handler to avoid storm in pathological cases ] Signed-off-by: Josh Poimboeuf Reviewed-by: Jiri Slaby Signed-off-by: Jiri Kosina --- include/linux/livepatch.h | 4 +- kernel/livepatch/core.c | 170 ++++++++++++++++++++++++++++++++-------------- 2 files changed, 121 insertions(+), 53 deletions(-) (limited to 'include/linux/livepatch.h') diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 950bc615842f..f14c6fb262b4 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -40,8 +40,8 @@ enum klp_state { * @old_addr: a hint conveying at what address the old function * can be found (optional, vmlinux patches only) * @kobj: kobject for sysfs resources - * @fops: ftrace operations structure * @state: tracks function-level patch application state + * @stack_node: list node for klp_ops func_stack list */ struct klp_func { /* external */ @@ -59,8 +59,8 @@ struct klp_func { /* internal */ struct kobject kobj; - struct ftrace_ops *fops; enum klp_state state; + struct list_head stack_node; }; /** diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 2401e7f955d3..bc05d390ce85 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -29,17 +29,53 @@ #include #include -/* - * The klp_mutex protects the klp_patches list and state transitions of any - * structure reachable from the patches list. References to any structure must - * be obtained under mutex protection. +/** + * struct klp_ops - structure for tracking registered ftrace ops structs + * + * A single ftrace_ops is shared between all enabled replacement functions + * (klp_func structs) which have the same old_addr. This allows the switch + * between function versions to happen instantaneously by updating the klp_ops + * struct's func_stack list. The winner is the klp_func at the top of the + * func_stack (front of the list). + * + * @node: node for the global klp_ops list + * @func_stack: list head for the stack of klp_func's (active func is on top) + * @fops: registered ftrace ops struct */ +struct klp_ops { + struct list_head node; + struct list_head func_stack; + struct ftrace_ops fops; +}; +/* + * The klp_mutex protects the global lists and state transitions of any + * structure reachable from them. References to any structure must be obtained + * under mutex protection (except in klp_ftrace_handler(), which uses RCU to + * ensure it gets consistent data). + */ static DEFINE_MUTEX(klp_mutex); + static LIST_HEAD(klp_patches); +static LIST_HEAD(klp_ops); static struct kobject *klp_root_kobj; +static struct klp_ops *klp_find_ops(unsigned long old_addr) +{ + struct klp_ops *ops; + struct klp_func *func; + + list_for_each_entry(ops, &klp_ops, node) { + func = list_first_entry(&ops->func_stack, struct klp_func, + stack_node); + if (func->old_addr == old_addr) + return ops; + } + + return NULL; +} + static bool klp_is_module(struct klp_object *obj) { return obj->name; @@ -267,16 +303,28 @@ static int klp_write_object_relocations(struct module *pmod, static void notrace klp_ftrace_handler(unsigned long ip, unsigned long parent_ip, - struct ftrace_ops *ops, + struct ftrace_ops *fops, struct pt_regs *regs) { - struct klp_func *func = ops->private; + struct klp_ops *ops; + struct klp_func *func; + + ops = container_of(fops, struct klp_ops, fops); + + rcu_read_lock(); + func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, + stack_node); + rcu_read_unlock(); + + if (WARN_ON_ONCE(!func)) + return; klp_arch_set_pc(regs, (unsigned long)func->new_func); } static int klp_disable_func(struct klp_func *func) { + struct klp_ops *ops; int ret; if (WARN_ON(func->state != KLP_ENABLED)) @@ -285,16 +333,28 @@ static int klp_disable_func(struct klp_func *func) if (WARN_ON(!func->old_addr)) return -EINVAL; - ret = unregister_ftrace_function(func->fops); - if (ret) { - pr_err("failed to unregister ftrace handler for function '%s' (%d)\n", - func->old_name, ret); - return ret; - } + ops = klp_find_ops(func->old_addr); + if (WARN_ON(!ops)) + return -EINVAL; - ret = ftrace_set_filter_ip(func->fops, func->old_addr, 1, 0); - if (ret) - pr_warn("function unregister succeeded but failed to clear the filter\n"); + if (list_is_singular(&ops->func_stack)) { + ret = unregister_ftrace_function(&ops->fops); + if (ret) { + pr_err("failed to unregister ftrace handler for function '%s' (%d)\n", + func->old_name, ret); + return ret; + } + + ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); + if (ret) + pr_warn("function unregister succeeded but failed to clear the filter\n"); + + list_del_rcu(&func->stack_node); + list_del(&ops->node); + kfree(ops); + } else { + list_del_rcu(&func->stack_node); + } func->state = KLP_DISABLED; @@ -303,6 +363,7 @@ static int klp_disable_func(struct klp_func *func) static int klp_enable_func(struct klp_func *func) { + struct klp_ops *ops; int ret; if (WARN_ON(!func->old_addr)) @@ -311,22 +372,50 @@ static int klp_enable_func(struct klp_func *func) if (WARN_ON(func->state != KLP_DISABLED)) return -EINVAL; - ret = ftrace_set_filter_ip(func->fops, func->old_addr, 0, 0); - if (ret) { - pr_err("failed to set ftrace filter for function '%s' (%d)\n", - func->old_name, ret); - return ret; - } + ops = klp_find_ops(func->old_addr); + if (!ops) { + ops = kzalloc(sizeof(*ops), GFP_KERNEL); + if (!ops) + return -ENOMEM; + + ops->fops.func = klp_ftrace_handler; + ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS | + FTRACE_OPS_FL_DYNAMIC | + FTRACE_OPS_FL_IPMODIFY; + + list_add(&ops->node, &klp_ops); + + INIT_LIST_HEAD(&ops->func_stack); + list_add_rcu(&func->stack_node, &ops->func_stack); + + ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0); + if (ret) { + pr_err("failed to set ftrace filter for function '%s' (%d)\n", + func->old_name, ret); + goto err; + } + + ret = register_ftrace_function(&ops->fops); + if (ret) { + pr_err("failed to register ftrace handler for function '%s' (%d)\n", + func->old_name, ret); + ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); + goto err; + } + - ret = register_ftrace_function(func->fops); - if (ret) { - pr_err("failed to register ftrace handler for function '%s' (%d)\n", - func->old_name, ret); - ftrace_set_filter_ip(func->fops, func->old_addr, 1, 0); } else { - func->state = KLP_ENABLED; + list_add_rcu(&func->stack_node, &ops->func_stack); } + func->state = KLP_ENABLED; + + return ret; + +err: + list_del_rcu(&func->stack_node); + list_del(&ops->node); + kfree(ops); return ret; } @@ -582,10 +671,6 @@ static struct kobj_type klp_ktype_patch = { static void klp_kobj_release_func(struct kobject *kobj) { - struct klp_func *func; - - func = container_of(kobj, struct klp_func, kobj); - kfree(func->fops); } static struct kobj_type klp_ktype_func = { @@ -642,28 +727,11 @@ static void klp_free_patch(struct klp_patch *patch) static int klp_init_func(struct klp_object *obj, struct klp_func *func) { - struct ftrace_ops *ops; - int ret; - - ops = kzalloc(sizeof(*ops), GFP_KERNEL); - if (!ops) - return -ENOMEM; - - ops->private = func; - ops->func = klp_ftrace_handler; - ops->flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_DYNAMIC | - FTRACE_OPS_FL_IPMODIFY; - func->fops = ops; + INIT_LIST_HEAD(&func->stack_node); func->state = KLP_DISABLED; - ret = kobject_init_and_add(&func->kobj, &klp_ktype_func, - obj->kobj, func->old_name); - if (ret) { - kfree(func->fops); - return ret; - } - - return 0; + return kobject_init_and_add(&func->kobj, &klp_ktype_func, + obj->kobj, func->old_name); } /* parts of the initialization that is done only when the object is loaded */ -- cgit From 12cf89b550d13eb7cb86ef182bd6c04345a33a1f Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Tue, 3 Feb 2015 16:45:18 -0600 Subject: livepatch: rename config to CONFIG_LIVEPATCH Rename CONFIG_LIVE_PATCHING to CONFIG_LIVEPATCH to make the naming of the config and the code more consistent. Signed-off-by: Josh Poimboeuf Reviewed-by: Jingoo Han Signed-off-by: Jiri Kosina --- arch/x86/Kconfig | 2 +- arch/x86/include/asm/livepatch.h | 4 ++-- arch/x86/kernel/Makefile | 2 +- include/linux/livepatch.h | 4 ++-- kernel/livepatch/Kconfig | 6 +++--- kernel/livepatch/Makefile | 2 +- samples/Kconfig | 4 ++-- samples/livepatch/Makefile | 2 +- 8 files changed, 13 insertions(+), 13 deletions(-) (limited to 'include/linux/livepatch.h') diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 29b095231276..11970b076862 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -17,7 +17,7 @@ config X86_64 depends on 64BIT select X86_DEV_DMA_OPS select ARCH_USE_CMPXCHG_LOCKREF - select HAVE_LIVE_PATCHING + select HAVE_LIVEPATCH ### Arch settings config X86 diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h index 26e58134c8cb..a455a53d789a 100644 --- a/arch/x86/include/asm/livepatch.h +++ b/arch/x86/include/asm/livepatch.h @@ -24,7 +24,7 @@ #include #include -#ifdef CONFIG_LIVE_PATCHING +#ifdef CONFIG_LIVEPATCH static inline int klp_check_compiler_support(void) { #ifndef CC_USING_FENTRY @@ -40,7 +40,7 @@ static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip) regs->ip = ip; } #else -#error Live patching support is disabled; check CONFIG_LIVE_PATCHING +#error Live patching support is disabled; check CONFIG_LIVEPATCH #endif #endif /* _ASM_X86_LIVEPATCH_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 316b34e74c15..732223496968 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -63,7 +63,7 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o obj-y += apic/ obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o -obj-$(CONFIG_LIVE_PATCHING) += livepatch.o +obj-$(CONFIG_LIVEPATCH) += livepatch.o obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o obj-$(CONFIG_X86_TSC) += trace_clock.o diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index f14c6fb262b4..95023fd8b00d 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -24,7 +24,7 @@ #include #include -#if IS_ENABLED(CONFIG_LIVE_PATCHING) +#if IS_ENABLED(CONFIG_LIVEPATCH) #include @@ -128,6 +128,6 @@ extern int klp_unregister_patch(struct klp_patch *); extern int klp_enable_patch(struct klp_patch *); extern int klp_disable_patch(struct klp_patch *); -#endif /* CONFIG_LIVE_PATCHING */ +#endif /* CONFIG_LIVEPATCH */ #endif /* _LINUX_LIVEPATCH_H_ */ diff --git a/kernel/livepatch/Kconfig b/kernel/livepatch/Kconfig index 347ee2221137..045022557936 100644 --- a/kernel/livepatch/Kconfig +++ b/kernel/livepatch/Kconfig @@ -1,15 +1,15 @@ -config HAVE_LIVE_PATCHING +config HAVE_LIVEPATCH bool help Arch supports kernel live patching -config LIVE_PATCHING +config LIVEPATCH bool "Kernel Live Patching" depends on DYNAMIC_FTRACE_WITH_REGS depends on MODULES depends on SYSFS depends on KALLSYMS_ALL - depends on HAVE_LIVE_PATCHING + depends on HAVE_LIVEPATCH help Say Y here if you want to support kernel live patching. This option has no runtime impact until a kernel "patch" diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile index 7c1f00861428..e8780c0901d9 100644 --- a/kernel/livepatch/Makefile +++ b/kernel/livepatch/Makefile @@ -1,3 +1,3 @@ -obj-$(CONFIG_LIVE_PATCHING) += livepatch.o +obj-$(CONFIG_LIVEPATCH) += livepatch.o livepatch-objs := core.o diff --git a/samples/Kconfig b/samples/Kconfig index 0aed20df5f0b..224ebb46bed5 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -63,9 +63,9 @@ config SAMPLE_RPMSG_CLIENT to communicate with an AMP-configured remote processor over the rpmsg bus. -config SAMPLE_LIVE_PATCHING +config SAMPLE_LIVEPATCH tristate "Build live patching sample -- loadable modules only" - depends on LIVE_PATCHING && m + depends on LIVEPATCH && m help Builds a sample live patch that replaces the procfs handler for /proc/cmdline to print "this has been live patched". diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile index 7f1cdc131a02..10319d7ea0b1 100644 --- a/samples/livepatch/Makefile +++ b/samples/livepatch/Makefile @@ -1 +1 @@ -obj-$(CONFIG_SAMPLE_LIVE_PATCHING) += livepatch-sample.o +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-sample.o -- cgit