virt_addr_valid() could be insufficient to validate the virt addr
on some architecture, which could lead to potential BUG which has
been found on arm64/powerpc64.

Let's add WARN_ON to check if the virt addr is passed virt_addr_valid()
but is a vmalloc/module address.

Signed-off-by: Kefeng Wang <redacted>
---
 mm/usercopy.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/usercopy.c b/mm/usercopy.c
index b3de3c4eefba..ce83e0b137dd 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c

@@ -228,6 +228,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 	if (!virt_addr_valid(ptr))
 		return;
 
+	WARN_ON_ONCE(is_vmalloc_or_module_addr(ptr));
+
 	/*
 	 * When CONFIG_HIGHMEM=y, kmap_to_page() will give either the
 	 * highmem page or fallback to virt_to_page(). The following

-- 
2.26.2