diff options
Diffstat (limited to 'kernel/livepatch')
| -rw-r--r-- | kernel/livepatch/Makefile | 2 | ||||
| -rw-r--r-- | kernel/livepatch/core.c | 112 | ||||
| -rw-r--r-- | kernel/livepatch/core.h | 41 | ||||
| -rw-r--r-- | kernel/livepatch/patch.c | 1 | ||||
| -rw-r--r-- | kernel/livepatch/patch.h | 1 | ||||
| -rw-r--r-- | kernel/livepatch/shadow.c | 277 | ||||
| -rw-r--r-- | kernel/livepatch/transition.c | 45 | ||||
| -rw-r--r-- | kernel/livepatch/transition.h | 1 |
8 files changed, 439 insertions, 41 deletions
diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile index 2b8bdb1925da..b36ceda6488e 100644 --- a/kernel/livepatch/Makefile +++ b/kernel/livepatch/Makefile @@ -1,3 +1,3 @@ obj-$(CONFIG_LIVEPATCH) += livepatch.o -livepatch-objs := core.o patch.o transition.o +livepatch-objs := core.o patch.o shadow.o transition.o diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index b9628e43c78f..de9e45dca70f 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -54,11 +54,6 @@ static bool klp_is_module(struct klp_object *obj) return obj->name; } -static bool klp_is_object_loaded(struct klp_object *obj) -{ - return !obj->name || obj->mod; -} - /* sets obj->mod if object is not vmlinux and module is found */ static void klp_find_object_module(struct klp_object *obj) { @@ -285,6 +280,11 @@ static int klp_write_object_relocations(struct module *pmod, static int __klp_disable_patch(struct klp_patch *patch) { + struct klp_object *obj; + + if (WARN_ON(!patch->enabled)) + return -EINVAL; + if (klp_transition_patch) return -EBUSY; @@ -295,6 +295,10 @@ static int __klp_disable_patch(struct klp_patch *patch) klp_init_transition(patch, KLP_UNPATCHED); + klp_for_each_object(patch, obj) + if (obj->patched) + klp_pre_unpatch_callback(obj); + /* * Enforce the order of the func->transition writes in * klp_init_transition() and the TIF_PATCH_PENDING writes in @@ -388,13 +392,18 @@ static int __klp_enable_patch(struct klp_patch *patch) if (!klp_is_object_loaded(obj)) continue; - ret = klp_patch_object(obj); + ret = klp_pre_patch_callback(obj); if (ret) { - pr_warn("failed to enable patch '%s'\n", - patch->mod->name); + pr_warn("pre-patch callback failed for object '%s'\n", + klp_is_module(obj) ? obj->name : "vmlinux"); + goto err; + } - klp_cancel_transition(); - return ret; + ret = klp_patch_object(obj); + if (ret) { + pr_warn("failed to patch object '%s'\n", + klp_is_module(obj) ? obj->name : "vmlinux"); + goto err; } } @@ -403,6 +412,11 @@ static int __klp_enable_patch(struct klp_patch *patch) patch->enabled = true; return 0; +err: + pr_warn("failed to enable patch '%s'\n", patch->mod->name); + + klp_cancel_transition(); + return ret; } /** @@ -830,6 +844,47 @@ int klp_register_patch(struct klp_patch *patch) } EXPORT_SYMBOL_GPL(klp_register_patch); +/* + * Remove parts of patches that touch a given kernel module. The list of + * patches processed might be limited. When limit is NULL, all patches + * will be handled. + */ +static void klp_cleanup_module_patches_limited(struct module *mod, + struct klp_patch *limit) +{ + struct klp_patch *patch; + struct klp_object *obj; + + list_for_each_entry(patch, &klp_patches, list) { + if (patch == limit) + break; + + klp_for_each_object(patch, obj) { + if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) + continue; + + /* + * Only unpatch the module if the patch is enabled or + * is in transition. + */ + if (patch->enabled || patch == klp_transition_patch) { + + if (patch != klp_transition_patch) + klp_pre_unpatch_callback(obj); + + pr_notice("reverting patch '%s' on unloading module '%s'\n", + patch->mod->name, obj->mod->name); + klp_unpatch_object(obj); + + klp_post_unpatch_callback(obj); + } + + klp_free_object_loaded(obj); + break; + } + } +} + int klp_module_coming(struct module *mod) { int ret; @@ -871,13 +926,25 @@ int klp_module_coming(struct module *mod) pr_notice("applying patch '%s' to loading module '%s'\n", patch->mod->name, obj->mod->name); + ret = klp_pre_patch_callback(obj); + if (ret) { + pr_warn("pre-patch callback failed for object '%s'\n", + obj->name); + goto err; + } + ret = klp_patch_object(obj); if (ret) { pr_warn("failed to apply patch '%s' to module '%s' (%d)\n", patch->mod->name, obj->mod->name, ret); + + klp_post_unpatch_callback(obj); goto err; } + if (patch != klp_transition_patch) + klp_post_patch_callback(obj); + break; } } @@ -894,7 +961,7 @@ err: pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n", patch->mod->name, obj->mod->name, obj->mod->name); mod->klp_alive = false; - klp_free_object_loaded(obj); + klp_cleanup_module_patches_limited(mod, patch); mutex_unlock(&klp_mutex); return ret; @@ -902,9 +969,6 @@ err: void klp_module_going(struct module *mod) { - struct klp_patch *patch; - struct klp_object *obj; - if (WARN_ON(mod->state != MODULE_STATE_GOING && mod->state != MODULE_STATE_COMING)) return; @@ -917,25 +981,7 @@ void klp_module_going(struct module *mod) */ mod->klp_alive = false; - list_for_each_entry(patch, &klp_patches, list) { - klp_for_each_object(patch, obj) { - if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) - continue; - - /* - * Only unpatch the module if the patch is enabled or - * is in transition. - */ - if (patch->enabled || patch == klp_transition_patch) { - pr_notice("reverting patch '%s' on unloading module '%s'\n", - patch->mod->name, obj->mod->name); - klp_unpatch_object(obj); - } - - klp_free_object_loaded(obj); - break; - } - } + klp_cleanup_module_patches_limited(mod, NULL); mutex_unlock(&klp_mutex); } diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h index c74f24c47837..48a83d4364cf 100644 --- a/kernel/livepatch/core.h +++ b/kernel/livepatch/core.h @@ -1,6 +1,47 @@ +/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LIVEPATCH_CORE_H #define _LIVEPATCH_CORE_H +#include <linux/livepatch.h> + extern struct mutex klp_mutex; +static inline bool klp_is_object_loaded(struct klp_object *obj) +{ + return !obj->name || obj->mod; +} + +static inline int klp_pre_patch_callback(struct klp_object *obj) +{ + int ret = 0; + + if (obj->callbacks.pre_patch) + ret = (*obj->callbacks.pre_patch)(obj); + + obj->callbacks.post_unpatch_enabled = !ret; + + return ret; +} + +static inline void klp_post_patch_callback(struct klp_object *obj) +{ + if (obj->callbacks.post_patch) + (*obj->callbacks.post_patch)(obj); +} + +static inline void klp_pre_unpatch_callback(struct klp_object *obj) +{ + if (obj->callbacks.pre_unpatch) + (*obj->callbacks.pre_unpatch)(obj); +} + +static inline void klp_post_unpatch_callback(struct klp_object *obj) +{ + if (obj->callbacks.post_unpatch_enabled && + obj->callbacks.post_unpatch) + (*obj->callbacks.post_unpatch)(obj); + + obj->callbacks.post_unpatch_enabled = false; +} + #endif /* _LIVEPATCH_CORE_H */ diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c index 52c4e907c14b..82d584225dc6 100644 --- a/kernel/livepatch/patch.c +++ b/kernel/livepatch/patch.c @@ -28,6 +28,7 @@ #include <linux/slab.h> #include <linux/bug.h> #include <linux/printk.h> +#include "core.h" #include "patch.h" #include "transition.h" diff --git a/kernel/livepatch/patch.h b/kernel/livepatch/patch.h index 0db227170c36..e72d8250d04b 100644 --- a/kernel/livepatch/patch.h +++ b/kernel/livepatch/patch.h @@ -1,3 +1,4 @@ +/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LIVEPATCH_PATCH_H #define _LIVEPATCH_PATCH_H diff --git a/kernel/livepatch/shadow.c b/kernel/livepatch/shadow.c new file mode 100644 index 000000000000..fdac27588d60 --- /dev/null +++ b/kernel/livepatch/shadow.c @@ -0,0 +1,277 @@ +/* + * shadow.c - Shadow Variables + * + * Copyright (C) 2014 Josh Poimboeuf <jpoimboe@redhat.com> + * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> + * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> + * + * 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 <http://www.gnu.org/licenses/>. + */ + +/** + * DOC: Shadow variable API concurrency notes: + * + * The shadow variable API provides a simple relationship between an + * <obj, id> pair and a pointer value. It is the responsibility of the + * caller to provide any mutual exclusion required of the shadow data. + * + * Once a shadow variable is attached to its parent object via the + * klp_shadow_*alloc() API calls, it is considered live: any subsequent + * call to klp_shadow_get() may then return the shadow variable's data + * pointer. Callers of klp_shadow_*alloc() should prepare shadow data + * accordingly. + * + * The klp_shadow_*alloc() API calls may allocate memory for new shadow + * variable structures. Their implementation does not call kmalloc + * inside any spinlocks, but API callers should pass GFP flags according + * to their specific needs. + * + * The klp_shadow_hash is an RCU-enabled hashtable and is safe against + * concurrent klp_shadow_free() and klp_shadow_get() operations. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/hashtable.h> +#include <linux/slab.h> +#include <linux/livepatch.h> + +static DEFINE_HASHTABLE(klp_shadow_hash, 12); + +/* + * klp_shadow_lock provides exclusive access to the klp_shadow_hash and + * the shadow variables it references. + */ +static DEFINE_SPINLOCK(klp_shadow_lock); + +/** + * struct klp_shadow - shadow variable structure + * @node: klp_shadow_hash hash table node + * @rcu_head: RCU is used to safely free this structure + * @obj: pointer to parent object + * @id: data identifier + * @data: data area + */ +struct klp_shadow { + struct hlist_node node; + struct rcu_head rcu_head; + void *obj; + unsigned long id; + char data[]; +}; + +/** + * klp_shadow_match() - verify a shadow variable matches given <obj, id> + * @shadow: shadow variable to match + * @obj: pointer to parent object + * @id: data identifier + * + * Return: true if the shadow variable matches. + */ +static inline bool klp_shadow_match(struct klp_shadow *shadow, void *obj, + unsigned long id) +{ + return shadow->obj == obj && shadow->id == id; +} + +/** + * klp_shadow_get() - retrieve a shadow variable data pointer + * @obj: pointer to parent object + * @id: data identifier + * + * Return: the shadow variable data element, NULL on failure. + */ +void *klp_shadow_get(void *obj, unsigned long id) +{ + struct klp_shadow *shadow; + + rcu_read_lock(); + + hash_for_each_possible_rcu(klp_shadow_hash, shadow, node, + (unsigned long)obj) { + + if (klp_shadow_match(shadow, obj, id)) { + rcu_read_unlock(); + return shadow->data; + } + } + + rcu_read_unlock(); + + return NULL; +} +EXPORT_SYMBOL_GPL(klp_shadow_get); + +static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data, + size_t size, gfp_t gfp_flags, bool warn_on_exist) +{ + struct klp_shadow *new_shadow; + void *shadow_data; + unsigned long flags; + + /* Check if the shadow variable already exists */ + shadow_data = klp_shadow_get(obj, id); + if (shadow_data) + goto exists; + + /* Allocate a new shadow variable for use inside the lock below */ + new_shadow = kzalloc(size + sizeof(*new_shadow), gfp_flags); + if (!new_shadow) + return NULL; + + new_shadow->obj = obj; + new_shadow->id = id; + + /* Initialize the shadow variable if data provided */ + if (data) + memcpy(new_shadow->data, data, size); + + /* Look for <obj, id> again under the lock */ + spin_lock_irqsave(&klp_shadow_lock, flags); + shadow_data = klp_shadow_get(obj, id); + if (unlikely(shadow_data)) { + /* + * Shadow variable was found, throw away speculative + * allocation. + */ + spin_unlock_irqrestore(&klp_shadow_lock, flags); + kfree(new_shadow); + goto exists; + } + + /* No <obj, id> found, so attach the newly allocated one */ + hash_add_rcu(klp_shadow_hash, &new_shadow->node, + (unsigned long)new_shadow->obj); + spin_unlock_irqrestore(&klp_shadow_lock, flags); + + return new_shadow->data; + +exists: + if (warn_on_exist) { + WARN(1, "Duplicate shadow variable <%p, %lx>\n", obj, id); + return NULL; + } + + return shadow_data; +} + +/** + * klp_shadow_alloc() - allocate and add a new shadow variable + * @obj: pointer to parent object + * @id: data identifier + * @data: pointer to data to attach to parent + * @size: size of attached data + * @gfp_flags: GFP mask for allocation + * + * Allocates @size bytes for new shadow variable data using @gfp_flags + * and copies @size bytes from @data into the new shadow variable's own + * data space. If @data is NULL, @size bytes are still allocated, but + * no copy is performed. The new shadow variable is then added to the + * global hashtable. + * + * If an existing <obj, id> shadow variable can be found, this routine + * will issue a WARN, exit early and return NULL. + * + * Return: the shadow variable data element, NULL on duplicate or + * failure. + */ +void *klp_shadow_alloc(void *obj, unsigned long id, void *data, + size_t size, gfp_t gfp_flags) +{ + return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, true); +} +EXPORT_SYMBOL_GPL(klp_shadow_alloc); + +/** + * klp_shadow_get_or_alloc() - get existing or allocate a new shadow variable + * @obj: pointer to parent object + * @id: data identifier + * @data: pointer to data to attach to parent + * @size: size of attached data + * @gfp_flags: GFP mask for allocation + * + * Returns a pointer to existing shadow data if an <obj, id> shadow + * variable is already present. Otherwise, it creates a new shadow + * variable like klp_shadow_alloc(). + * + * This function guarantees that only one shadow variable exists with + * the given @id for the given @obj. It also guarantees that the shadow + * variable will be initialized by the given @data only when it did not + * exist before. + * + * Return: the shadow variable data element, NULL on failure. + */ +void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data, + size_t size, gfp_t gfp_flags) +{ + return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, false); +} +EXPORT_SYMBOL_GPL(klp_shadow_get_or_alloc); + +/** + * klp_shadow_free() - detach and free a <obj, id> shadow variable + * @obj: pointer to parent object + * @id: data identifier + * + * This function releases the memory for this <obj, id> shadow variable + * instance, callers should stop referencing it accordingly. + */ +void klp_shadow_free(void *obj, unsigned long id) +{ + struct klp_shadow *shadow; + unsigned long flags; + + spin_lock_irqsave(&klp_shadow_lock, flags); + + /* Delete <obj, id> from hash */ + hash_for_each_possible(klp_shadow_hash, shadow, node, + (unsigned long)obj) { + + if (klp_shadow_match(shadow, obj, id)) { + hash_del_rcu(&shadow->node); + kfree_rcu(shadow, rcu_head); + break; + } + } + + spin_unlock_irqrestore(&klp_shadow_lock, flags); +} +EXPORT_SYMBOL_GPL(klp_shadow_free); + +/** + * klp_shadow_free_all() - detach and free all <*, id> shadow variables + * @id: data identifier + * + * This function releases the memory for all <*, id> shadow variable + * instances, callers should stop referencing them accordingly. + */ +void klp_shadow_free_all(unsigned long id) +{ + struct klp_shadow *shadow; + unsigned long flags; + int i; + + spin_lock_irqsave(&klp_shadow_lock, flags); + + /* Delete all <*, id> from hash */ + hash_for_each(klp_shadow_hash, i, shadow, node) { + if (klp_shadow_match(shadow, shadow->obj, id)) { + hash_del_rcu(&shadow->node); + kfree_rcu(shadow, rcu_head); + } + } + + spin_unlock_irqrestore(&klp_shadow_lock, flags); +} +EXPORT_SYMBOL_GPL(klp_shadow_free_all); diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c index b004a1fb6032..56add6327736 100644 --- a/kernel/livepatch/transition.c +++ b/kernel/livepatch/transition.c @@ -82,6 +82,10 @@ static void klp_complete_transition(void) unsigned int cpu; bool immediate_func = false; + pr_debug("'%s': completing %s transition\n", + klp_transition_patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); + if (klp_target_state == KLP_UNPATCHED) { /* * All tasks have transitioned to KLP_UNPATCHED so we can now @@ -109,9 +113,6 @@ static void klp_complete_transition(void) } } - if (klp_target_state == KLP_UNPATCHED && !immediate_func) - module_put(klp_transition_patch->mod); - /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */ if (klp_target_state == KLP_PATCHED) klp_synchronize_transition(); @@ -130,6 +131,27 @@ static void klp_complete_transition(void) } done: + klp_for_each_object(klp_transition_patch, obj) { + if (!klp_is_object_loaded(obj)) + continue; + if (klp_target_state == KLP_PATCHED) + klp_post_patch_callback(obj); + else if (klp_target_state == KLP_UNPATCHED) + klp_post_unpatch_callback(obj); + } + + pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); + + /* + * See complementary comment in __klp_enable_patch() for why we + * keep the module reference for immediate patches. + */ + if (!klp_transition_patch->immediate && !immediate_func && + klp_target_state == KLP_UNPATCHED) { + module_put(klp_transition_patch->mod); + } + klp_target_state = KLP_UNDEFINED; klp_transition_patch = NULL; } @@ -145,6 +167,9 @@ void klp_cancel_transition(void) if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED)) return; + pr_debug("'%s': canceling patching transition, going to unpatch\n", + klp_transition_patch->mod->name); + klp_target_state = KLP_UNPATCHED; klp_complete_transition(); } @@ -408,9 +433,6 @@ void klp_try_complete_transition(void) } success: - pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, - klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); - /* we're done, now cleanup the data structures */ klp_complete_transition(); } @@ -426,7 +448,8 @@ void klp_start_transition(void) WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); - pr_notice("'%s': %s...\n", klp_transition_patch->mod->name, + pr_notice("'%s': starting %s transition\n", + klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); /* @@ -482,6 +505,9 @@ void klp_init_transition(struct klp_patch *patch, int state) */ klp_target_state = state; + pr_debug("'%s': initializing %s transition\n", patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); + /* * If the patch can be applied or reverted immediately, skip the * per-task transitions. @@ -547,6 +573,11 @@ void klp_reverse_transition(void) unsigned int cpu; struct task_struct *g, *task; + pr_debug("'%s': reversing transition from %s\n", + klp_transition_patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching to unpatching" : + "unpatching to patching"); + klp_transition_patch->enabled = !klp_transition_patch->enabled; klp_target_state = !klp_target_state; diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h index ce09b326546c..0f6e27c481f9 100644 --- a/kernel/livepatch/transition.h +++ b/kernel/livepatch/transition.h @@ -1,3 +1,4 @@ +/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LIVEPATCH_TRANSITION_H #define _LIVEPATCH_TRANSITION_H |