[PATCH v5 16/44] kmsan: handle task creation and exiting

[Alexander Potapenko]

Tell KMSAN that a new task is created, so the tool creates a backing
metadata structure for that task.

Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
v2:
 -- move implementation of kmsan_task_create() and kmsan_task_exit() here

v4:
 -- change sizeof(type) to sizeof(*ptr)

v5:
 -- do not export KMSAN hooks that are not called from modules
 -- minor comment fix

Link: https://linux-review.googlesource.com/id/I0f41c3a1c7d66f7e14aabcfdfc7c69addb945805
---
 include/linux/kmsan.h | 21 +++++++++++++++++++++
 kernel/exit.c         |  2 ++
 kernel/fork.c         |  2 ++
 mm/kmsan/core.c       | 10 ++++++++++
 mm/kmsan/hooks.c      | 17 +++++++++++++++++
 mm/kmsan/kmsan.h      |  2 ++
 6 files changed, 54 insertions(+)

diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
index fd76cea338878..5ec056380a43b 100644
--- a/include/linux/kmsan.h
+++ b/include/linux/kmsan.h
@@ -16,6 +16,7 @@
 
 struct page;
 struct kmem_cache;
+struct task_struct;
 
 #ifdef CONFIG_KMSAN
 
@@ -42,6 +43,18 @@ struct kmsan_ctx {
 	bool allow_reporting;
 };
 
+/**
+ * kmsan_task_create() - Initialize KMSAN state for the task.
+ * @task: task to initialize.
+ */
+void kmsan_task_create(struct task_struct *task);
+
+/**
+ * kmsan_task_exit() - Notify KMSAN that a task has exited.
+ * @task: task about to finish.
+ */
+void kmsan_task_exit(struct task_struct *task);
+
 /**
  * kmsan_alloc_page() - Notify KMSAN about an alloc_pages() call.
  * @page:  struct page pointer returned by alloc_pages().
@@ -163,6 +176,14 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
 
 #else
 
+static inline void kmsan_task_create(struct task_struct *task)
+{
+}
+
+static inline void kmsan_task_exit(struct task_struct *task)
+{
+}
+
 static inline int kmsan_alloc_page(struct page *page, unsigned int order,
 				   gfp_t flags)
 {
diff --git a/kernel/exit.c b/kernel/exit.c
index 84021b24f79e3..f5d620c315662 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -60,6 +60,7 @@
 #include <linux/writeback.h>
 #include <linux/shm.h>
 #include <linux/kcov.h>
+#include <linux/kmsan.h>
 #include <linux/random.h>
 #include <linux/rcuwait.h>
 #include <linux/compat.h>
@@ -741,6 +742,7 @@ void __noreturn do_exit(long code)
 	WARN_ON(tsk->plug);
 
 	kcov_task_exit(tsk);
+	kmsan_task_exit(tsk);
 
 	coredump_task_exit(tsk);
 	ptrace_event(PTRACE_EVENT_EXIT, code);
diff --git a/kernel/fork.c b/kernel/fork.c
index 90c85b17bf698..7cf3eea01ceef 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -37,6 +37,7 @@
 #include <linux/fdtable.h>
 #include <linux/iocontext.h>
 #include <linux/key.h>
+#include <linux/kmsan.h>
 #include <linux/binfmts.h>
 #include <linux/mman.h>
 #include <linux/mmu_notifier.h>
@@ -1026,6 +1027,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	tsk->worker_private = NULL;
 
 	kcov_task_init(tsk);
+	kmsan_task_create(tsk);
 	kmap_local_fork(tsk);
 
 #ifdef CONFIG_FAULT_INJECTION
diff --git a/mm/kmsan/core.c b/mm/kmsan/core.c
index a5dec6e62b4ef..a640e0cccbb64 100644
--- a/mm/kmsan/core.c
+++ b/mm/kmsan/core.c
@@ -44,6 +44,16 @@ bool kmsan_enabled __read_mostly;
  */
 DEFINE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx);
 
+void kmsan_internal_task_create(struct task_struct *task)
+{
+	struct kmsan_ctx *ctx = &task->kmsan_ctx;
+	struct thread_info *info = current_thread_info();
+
+	__memset(ctx, 0, sizeof(*ctx));
+	ctx->allow_reporting = true;
+	kmsan_internal_unpoison_memory(info, sizeof(*info), false);
+}
+
 void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags,
 				  unsigned int poison_flags)
 {
diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 519a7a1dcb4aa..4ab8c629acd0c 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -26,6 +26,23 @@
  * skipping effects of functions like memset() inside instrumented code.
  */
 
+void kmsan_task_create(struct task_struct *task)
+{
+	kmsan_enter_runtime();
+	kmsan_internal_task_create(task);
+	kmsan_leave_runtime();
+}
+
+void kmsan_task_exit(struct task_struct *task)
+{
+	struct kmsan_ctx *ctx = &task->kmsan_ctx;
+
+	if (!kmsan_enabled || kmsan_in_runtime())
+		return;
+
+	ctx->allow_reporting = false;
+}
+
 void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
 {
 	if (unlikely(object == NULL))
diff --git a/mm/kmsan/kmsan.h b/mm/kmsan/kmsan.h
index 6b9deee3b7f32..04954b83c5d65 100644
--- a/mm/kmsan/kmsan.h
+++ b/mm/kmsan/kmsan.h
@@ -179,6 +179,8 @@ void kmsan_internal_set_shadow_origin(void *address, size_t size, int b,
 				      u32 origin, bool checked);
 depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id);
 
+void kmsan_internal_task_create(struct task_struct *task);
+
 bool kmsan_metadata_is_contiguous(void *addr, size_t size);
 void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr,
 				 int reason);
-- 
2.37.2.672.g94769d06f0-goog