[PATCH 12/32] kmsan: Allow disabling KMSAN checks for the current task

Ilya Leoshkevich
2023-11-15T20:35:42Z

Like for KASAN, it's useful to temporarily disable KMSAN checks around,
e.g., redzone accesses. Introduce kmsan_disable_current() and
kmsan_enable_current(), which are similar to their KASAN counterparts.

Even though it's not strictly necessary, make them reentrant, in order
to match the KASAN behavior. Repurpose the allow_reporting field for
this.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
Documentation/dev-tools/kmsan.rst | 4 ++--
include/linux/kmsan-checks.h | 12 ++++++++++++
include/linux/kmsan_types.h | 2 +-
mm/kmsan/core.c | 2 +-
mm/kmsan/hooks.c | 14 +++++++++++++-
mm/kmsan/report.c | 6 +++---
6 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/Documentation/dev-tools/kmsan.rst b/Documentation/dev-tools/kmsan.rst
index 323eedad53cd..022a823f5f1b 100644
--- a/Documentation/dev-tools/kmsan.rst
+++ b/Documentation/dev-tools/kmsan.rst
@@ -338,11 +338,11 @@ Per-task KMSAN state
~~~~~~~~~~~~~~~~~~~~

Every task_struct has an associated KMSAN task state that holds the KMSAN
-context (see above) and a per-task flag disallowing KMSAN reports::
+context (see above) and a per-task counter disallowing KMSAN reports::

struct kmsan_context {
...
- bool allow_reporting;
+ unsigned int depth;
struct kmsan_context_state cstate;
...
}
diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h
index 5218973f0ad0..bab2603685f7 100644
--- a/include/linux/kmsan-checks.h
+++ b/include/linux/kmsan-checks.h
@@ -72,6 +72,10 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
*/
void kmsan_memmove_metadata(void *dst, const void *src, size_t n);

+void kmsan_enable_current(void);
+
+void kmsan_disable_current(void);
+
#else

static inline void kmsan_poison_memory(const void *address, size_t size,
@@ -92,6 +96,14 @@ static inline void kmsan_memmove_metadata(void *dst, const void *src, size_t n)
{
}

+static inline void kmsan_enable_current(void)
+{
+}
+
+static inline void kmsan_disable_current(void)
+{
+}
+
#endif

#endif /* _LINUX_KMSAN_CHECKS_H */
diff --git a/include/linux/kmsan_types.h b/include/linux/kmsan_types.h
index 8bfa6c98176d..27bb146ece95 100644
--- a/include/linux/kmsan_types.h
+++ b/include/linux/kmsan_types.h
@@ -29,7 +29,7 @@ struct kmsan_context_state {
struct kmsan_ctx {
struct kmsan_context_state cstate;
int kmsan_in_runtime;
- bool allow_reporting;
+ unsigned int depth;
};

#endif /* _LINUX_KMSAN_TYPES_H */
diff --git a/mm/kmsan/core.c b/mm/kmsan/core.c
index c19f47af0424..b8767378cf8a 100644
--- a/mm/kmsan/core.c
+++ b/mm/kmsan/core.c
@@ -43,7 +43,7 @@ void kmsan_internal_task_create(struct task_struct *task)
struct thread_info *info = current_thread_info();

__memset(ctx, 0, sizeof(*ctx));
- ctx->allow_reporting = true;
+ ctx->depth = 0;
kmsan_internal_unpoison_memory(info, sizeof(*info), false);
}

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 4d477a0a356c..7b5814412e9f 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -44,7 +44,7 @@ void kmsan_task_exit(struct task_struct *task)
if (!kmsan_enabled || kmsan_in_runtime())
return;

- ctx->allow_reporting = false;
+ ctx->depth++;
}

void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
@@ -434,3 +434,15 @@ void kmsan_check_memory(const void *addr, size_t size)
REASON_ANY);
}
EXPORT_SYMBOL(kmsan_check_memory);
+
+void kmsan_enable_current(void)
+{
+ current->kmsan_ctx.depth--;
+}
+EXPORT_SYMBOL(kmsan_enable_current);
+
+void kmsan_disable_current(void)
+{
+ current->kmsan_ctx.depth++;
+}
+EXPORT_SYMBOL(kmsan_disable_current);
diff --git a/mm/kmsan/report.c b/mm/kmsan/report.c
index c79d3b0d2d0d..edcf53ca428e 100644
--- a/mm/kmsan/report.c
+++ b/mm/kmsan/report.c
@@ -158,12 +158,12 @@ void kmsan_report(depot_stack_handle_t origin, void *address, int size,

if (!kmsan_enabled)
return;
- if (!current->kmsan_ctx.allow_reporting)
+ if (current->kmsan_ctx.depth)
return;
if (!origin)
return;

- current->kmsan_ctx.allow_reporting = false;
+ current->kmsan_ctx.depth++;
ua_flags = user_access_save();
raw_spin_lock(&kmsan_report_lock);
pr_err("=====================================================\n");
@@ -216,5 +216,5 @@ void kmsan_report(depot_stack_handle_t origin, void *address, int size,
if (panic_on_kmsan)
panic("kmsan.panic set ...\n");
user_access_restore(ua_flags);
- current->kmsan_ctx.allow_reporting = true;
+ current->kmsan_ctx.depth--;
}
--
2.41.0