[PATCH 4/5] kmsan: enter the runtime around kmsan_internal_memmove_metadata() call

Alexander Potapenko
2025-05-07T16:00:25Z

kmsan_internal_memmove_metadata() transitively calls stack_depot_save()
(via kmsan_internal_chain_origin() and kmsan_save_stack_with_flags()),
which may allocate memory. Guard it with kmsan_enter_runtime() and
kmsan_leave_runtime() to avoid recursion.

This bug was spotted by CONFIG_WARN_CAPABILITY_ANALYSIS=y

Cc: Marco Elver <elver@google.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Alexander Potapenko <glider@google.com>
---
mm/kmsan/hooks.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 05f2faa540545..97de3d6194f07 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -275,8 +275,10 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
* Don't check anything, just copy the shadow of the copied
* bytes.
*/
+ kmsan_enter_runtime();
kmsan_internal_memmove_metadata((void *)to, (void *)from,
to_copy - left);
+ kmsan_leave_runtime();
}
user_access_restore(ua_flags);
}
--
2.49.0.967.g6a0df3ecc3-goog