Move the compound page overrun detection out of
CONFIG_HARDENED_USERCOPY_PAGESPAN so it's enabled for more people.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/usercopy.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/usercopy.c b/mm/usercopy.c
index 7bfc4f9ed1e4..e395462961d5 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c

@@ -194,11 +194,6 @@ static inline void check_page_span(const void *ptr, unsigned long n,
 		   ((unsigned long)end & (unsigned long)PAGE_MASK)))
 		return;
 
-	/* Allow if fully inside the same compound (__GFP_COMP) page. */
-	endpage = virt_to_head_page(end);
-	if (likely(endpage == page))
-		return;
-
 	/*
 	 * Reject if range is entirely either Reserved (i.e. special or
 	 * device memory), or CMA. Otherwise, reject since the object spans

@@ -250,6 +245,10 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 	if (PageSlab(page)) {
 		/* Check slab allocator for flags and size. */
 		__check_heap_object(ptr, n, page, to_user);
+	} else if (PageHead(page)) {
+		/* A compound allocation */
+		if (ptr + n > page_address(page) + page_size(page))
+			usercopy_abort("page alloc", NULL, to_user, 0, n);