The patch titled
Subject: mm: kfence: pass a pointer to virt_to_page()
has been added to the -mm mm-unstable branch. Its filename is
mm-kfence-pass-a-pointer-to-virt_to_page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-kfence-pass-a-pointer-to-virt_to_page.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Linus Walleij <linus.walleij@xxxxxxxxxx>
Subject: mm: kfence: pass a pointer to virt_to_page()
Date: Thu, 30 Jun 2022 10:41:22 +0200
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.
Link: https://lkml.kernel.org/r/20220630084124.691207-4-linus.walleij@xxxxxxxxxx
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kfence/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/kfence/core.c~mm-kfence-pass-a-pointer-to-virt_to_page
+++ a/mm/kfence/core.c
@@ -546,7 +546,7 @@ static unsigned long kfence_init_pool(vo
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
@@ -660,7 +660,7 @@ 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
_
Patches currently in -mm which might be from linus.walleij@xxxxxxxxxx are
lib-test_free_pagesc-pass-a-pointer-to-virt_to_page.patch
mm-highmem-pass-a-pointer-to-virt_to_page.patch
mm-kfence-pass-a-pointer-to-virt_to_page.patch
mm-gup-pass-a-pointer-to-virt_to_page.patch
mm-nommu-pass-a-pointer-to-virt_to_page.patch
