[PATCH 3/5] mm: kfence: Pass a pointer to virt_to_page()

Linus Walleij
2022-06-30T08:43:55Z

Functions that work on a pointer to virtual memory such as
virt_to_pfn() and users of that function such as
virt_to_page() are supposed to pass a pointer to virtual
memory, ideally a (void *) or other pointer. However since
many architectures implement virt_to_pfn() as a macro,
this function becomes polymorphic and accepts both a
(unsigned long) and a (void *).

If we instead implement a proper virt_to_pfn(void *addr)
function the following happens (occurred on arch/arm):

mm/kfence/core.c:558:30: warning: passing argument 1
of 'virt_to_pfn' makes pointer from integer without a
cast [-Wint-conversion]

In one case we can refer to __kfence_pool directly (and
that is a proper (char *) pointer) and in the other call
site we use an explicit cast.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
mm/kfence/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 4e7cd4c8e687..153cde62ad72 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -543,7 +543,7 @@ static unsigned long kfence_init_pool(void)
if (!arch_kfence_init_pool())
return addr;

- pages = virt_to_page(addr);
+ pages = virt_to_page(__kfence_pool);

/*
* Set up object pages: they must have PG_slab set, to avoid freeing
@@ -657,7 +657,7 @@ static bool kfence_init_pool_late(void)
/* Same as above. */
free_size = KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool);
#ifdef CONFIG_CONTIG_ALLOC
- free_contig_range(page_to_pfn(virt_to_page(addr)), free_size / PAGE_SIZE);
+ free_contig_range(page_to_pfn(virt_to_page((void *)addr)), free_size / PAGE_SIZE);
#else
free_pages_exact((void *)addr, free_size);
#endif
--
2.36.1