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authorLinus Torvalds <torvalds@linux-foundation.org>2018-02-01 00:02:18 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-01 00:02:18 +0300
commite1c70f32386c4984ed8ca1a7aedb9bbff9ed3414 (patch)
tree09a9092c1ea56b1d9c218a77b2510036b509f225 /kernel
parent183b6366cf473ff0e706a6751adc082faa44843d (diff)
parentd05b695c25bf0d704c74e0e1375de893531b9424 (diff)
downloadlinux-e1c70f32386c4984ed8ca1a7aedb9bbff9ed3414.tar.xz
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching
Pull livepatching updates from Jiri Kosina: - handle 'infinitely'-long sleeping tasks, from Miroslav Benes - remove 'immediate' feature, as it turns out it doesn't provide the originally expected semantics, and brings more issues than value * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching: livepatch: add locking to force and signal functions livepatch: Remove immediate feature livepatch: force transition to finish livepatch: send a fake signal to all blocking tasks
Diffstat (limited to 'kernel')
-rw-r--r--kernel/livepatch/core.c76
-rw-r--r--kernel/livepatch/transition.c116
-rw-r--r--kernel/livepatch/transition.h2
-rw-r--r--kernel/signal.c4
4 files changed, 145 insertions, 53 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index de9e45dca70f..3a4656fb7047 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -366,11 +366,6 @@ static int __klp_enable_patch(struct klp_patch *patch)
/*
* A reference is taken on the patch module to prevent it from being
* unloaded.
- *
- * Note: For immediate (no consistency model) patches we don't allow
- * patch modules to unload since there is no safe/sane method to
- * determine if a thread is still running in the patched code contained
- * in the patch module once the ftrace registration is successful.
*/
if (!try_module_get(patch->mod))
return -ENODEV;
@@ -454,6 +449,8 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
* /sys/kernel/livepatch/<patch>
* /sys/kernel/livepatch/<patch>/enabled
* /sys/kernel/livepatch/<patch>/transition
+ * /sys/kernel/livepatch/<patch>/signal
+ * /sys/kernel/livepatch/<patch>/force
* /sys/kernel/livepatch/<patch>/<object>
* /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
*/
@@ -528,11 +525,73 @@ static ssize_t transition_show(struct kobject *kobj,
patch == klp_transition_patch);
}
+static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct klp_patch *patch;
+ int ret;
+ bool val;
+
+ ret = kstrtobool(buf, &val);
+ if (ret)
+ return ret;
+
+ if (!val)
+ return count;
+
+ mutex_lock(&klp_mutex);
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+ if (patch != klp_transition_patch) {
+ mutex_unlock(&klp_mutex);
+ return -EINVAL;
+ }
+
+ klp_send_signals();
+
+ mutex_unlock(&klp_mutex);
+
+ return count;
+}
+
+static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct klp_patch *patch;
+ int ret;
+ bool val;
+
+ ret = kstrtobool(buf, &val);
+ if (ret)
+ return ret;
+
+ if (!val)
+ return count;
+
+ mutex_lock(&klp_mutex);
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+ if (patch != klp_transition_patch) {
+ mutex_unlock(&klp_mutex);
+ return -EINVAL;
+ }
+
+ klp_force_transition();
+
+ mutex_unlock(&klp_mutex);
+
+ return count;
+}
+
static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
+static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
+static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
static struct attribute *klp_patch_attrs[] = {
&enabled_kobj_attr.attr,
&transition_kobj_attr.attr,
+ &signal_kobj_attr.attr,
+ &force_kobj_attr.attr,
NULL
};
@@ -830,12 +889,7 @@ int klp_register_patch(struct klp_patch *patch)
if (!klp_initialized())
return -ENODEV;
- /*
- * Architectures without reliable stack traces have to set
- * patch->immediate because there's currently no way to patch kthreads
- * with the consistency model.
- */
- if (!klp_have_reliable_stack() && !patch->immediate) {
+ if (!klp_have_reliable_stack()) {
pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
return -ENOSYS;
}
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 56add6327736..7c6631e693bc 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -33,6 +33,8 @@ struct klp_patch *klp_transition_patch;
static int klp_target_state = KLP_UNDEFINED;
+static bool klp_forced = false;
+
/*
* This work can be performed periodically to finish patching or unpatching any
* "straggler" tasks which failed to transition in the first attempt.
@@ -80,7 +82,6 @@ static void klp_complete_transition(void)
struct klp_func *func;
struct task_struct *g, *task;
unsigned int cpu;
- bool immediate_func = false;
pr_debug("'%s': completing %s transition\n",
klp_transition_patch->mod->name,
@@ -102,16 +103,9 @@ static void klp_complete_transition(void)
klp_synchronize_transition();
}
- if (klp_transition_patch->immediate)
- goto done;
-
- klp_for_each_object(klp_transition_patch, obj) {
- klp_for_each_func(obj, func) {
+ klp_for_each_object(klp_transition_patch, obj)
+ klp_for_each_func(obj, func)
func->transition = false;
- if (func->immediate)
- immediate_func = true;
- }
- }
/* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */
if (klp_target_state == KLP_PATCHED)
@@ -130,7 +124,6 @@ static void klp_complete_transition(void)
task->patch_state = KLP_UNDEFINED;
}
-done:
klp_for_each_object(klp_transition_patch, obj) {
if (!klp_is_object_loaded(obj))
continue;
@@ -144,13 +137,11 @@ done:
klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
/*
- * See complementary comment in __klp_enable_patch() for why we
- * keep the module reference for immediate patches.
+ * klp_forced set implies unbounded increase of module's ref count if
+ * the module is disabled/enabled in a loop.
*/
- if (!klp_transition_patch->immediate && !immediate_func &&
- klp_target_state == KLP_UNPATCHED) {
+ if (!klp_forced && klp_target_state == KLP_UNPATCHED)
module_put(klp_transition_patch->mod);
- }
klp_target_state = KLP_UNDEFINED;
klp_transition_patch = NULL;
@@ -218,9 +209,6 @@ static int klp_check_stack_func(struct klp_func *func,
struct klp_ops *ops;
int i;
- if (func->immediate)
- return 0;
-
for (i = 0; i < trace->nr_entries; i++) {
address = trace->entries[i];
@@ -383,13 +371,6 @@ void klp_try_complete_transition(void)
WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED);
/*
- * If the patch can be applied or reverted immediately, skip the
- * per-task transitions.
- */
- if (klp_transition_patch->immediate)
- goto success;
-
- /*
* Try to switch the tasks to the target patch state by walking their
* stacks and looking for any to-be-patched or to-be-unpatched
* functions. If such functions are found on a stack, or if the stack
@@ -432,7 +413,6 @@ void klp_try_complete_transition(void)
return;
}
-success:
/* we're done, now cleanup the data structures */
klp_complete_transition();
}
@@ -453,13 +433,6 @@ void klp_start_transition(void)
klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
/*
- * If the patch can be applied or reverted immediately, skip the
- * per-task transitions.
- */
- if (klp_transition_patch->immediate)
- return;
-
- /*
* Mark all normal tasks as needing a patch state update. They'll
* switch either in klp_try_complete_transition() or as they exit the
* kernel.
@@ -509,13 +482,6 @@ void klp_init_transition(struct klp_patch *patch, int state)
klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
/*
- * If the patch can be applied or reverted immediately, skip the
- * per-task transitions.
- */
- if (patch->immediate)
- return;
-
- /*
* Initialize all tasks to the initial patch state to prepare them for
* switching to the target state.
*/
@@ -608,3 +574,71 @@ void klp_copy_process(struct task_struct *child)
/* TIF_PATCH_PENDING gets copied in setup_thread_stack() */
}
+
+/*
+ * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.
+ * Kthreads with TIF_PATCH_PENDING set are woken up. Only admin can request this
+ * action currently.
+ */
+void klp_send_signals(void)
+{
+ struct task_struct *g, *task;
+
+ pr_notice("signaling remaining tasks\n");
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task) {
+ if (!klp_patch_pending(task))
+ continue;
+
+ /*
+ * There is a small race here. We could see TIF_PATCH_PENDING
+ * set and decide to wake up a kthread or send a fake signal.
+ * Meanwhile the task could migrate itself and the action
+ * would be meaningless. It is not serious though.
+ */
+ if (task->flags & PF_KTHREAD) {
+ /*
+ * Wake up a kthread which sleeps interruptedly and
+ * still has not been migrated.
+ */
+ wake_up_state(task, TASK_INTERRUPTIBLE);
+ } else {
+ /*
+ * Send fake signal to all non-kthread tasks which are
+ * still not migrated.
+ */
+ spin_lock_irq(&task->sighand->siglock);
+ signal_wake_up(task, 0);
+ spin_unlock_irq(&task->sighand->siglock);
+ }
+ }
+ read_unlock(&tasklist_lock);
+}
+
+/*
+ * Drop TIF_PATCH_PENDING of all tasks on admin's request. This forces an
+ * existing transition to finish.
+ *
+ * NOTE: klp_update_patch_state(task) requires the task to be inactive or
+ * 'current'. This is not the case here and the consistency model could be
+ * broken. Administrator, who is the only one to execute the
+ * klp_force_transitions(), has to be aware of this.
+ */
+void klp_force_transition(void)
+{
+ struct task_struct *g, *task;
+ unsigned int cpu;
+
+ pr_warn("forcing remaining tasks to the patched state\n");
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task)
+ klp_update_patch_state(task);
+ read_unlock(&tasklist_lock);
+
+ for_each_possible_cpu(cpu)
+ klp_update_patch_state(idle_task(cpu));
+
+ klp_forced = true;
+}
diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h
index 0f6e27c481f9..f9d0bc016067 100644
--- a/kernel/livepatch/transition.h
+++ b/kernel/livepatch/transition.h
@@ -11,5 +11,7 @@ void klp_cancel_transition(void);
void klp_start_transition(void);
void klp_try_complete_transition(void);
void klp_reverse_transition(void);
+void klp_send_signals(void);
+void klp_force_transition(void);
#endif /* _LIVEPATCH_TRANSITION_H */
diff --git a/kernel/signal.c b/kernel/signal.c
index e549174c0831..c6e4c83dc090 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -40,6 +40,7 @@
#include <linux/cn_proc.h>
#include <linux/compiler.h>
#include <linux/posix-timers.h>
+#include <linux/livepatch.h>
#define CREATE_TRACE_POINTS
#include <trace/events/signal.h>
@@ -165,7 +166,8 @@ void recalc_sigpending_and_wake(struct task_struct *t)
void recalc_sigpending(void)
{
- if (!recalc_sigpending_tsk(current) && !freezing(current))
+ if (!recalc_sigpending_tsk(current) && !freezing(current) &&
+ !klp_patch_pending(current))
clear_thread_flag(TIF_SIGPENDING);
}