[PATCH v7 16/43] kmsan: handle task creation and exiting

Alexander Potapenko
2022-09-15T15:07:53Z

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@google.com>
---
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 5c4e0079054e6..354aee6f7b1a2 100644
--- a/include/linux/kmsan.h
+++ b/include/linux/kmsan.h
@@ -15,9 +15,22 @@

struct page;
struct kmem_cache;
+struct task_struct;

#ifdef CONFIG_KMSAN

+/**
+ * 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().
@@ -139,6 +152,14 @@ 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 8a9e92068b150..a438f5ee3aed5 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 5330138fda5bc..112dce135c7f6 100644
--- a/mm/kmsan/core.c
+++ b/mm/kmsan/core.c
@@ -37,6 +37,16 @@ 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 000703c563a4d..6f3e64b0b61f8 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -27,6 +27,23 @@
* 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 97d48b45dba58..77ee068c04ae9 100644
--- a/mm/kmsan/kmsan.h
+++ b/mm/kmsan/kmsan.h
@@ -180,6 +180,8 @@ 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);
--
2.37.2.789.g6183377224-goog