Re: [PATCH 5.19 0767/1157] kasan: fix zeroing vmalloc memory with HW_TAGS
From: Jiri Slaby
Date: Tue Aug 16 2022 - 07:43:58 EST
On 16. 08. 22, 13:04, Jiri Slaby wrote:
On 15. 08. 22, 20:02, Greg Kroah-Hartman wrote:
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
[ Upstream commit 6c2f761dad7851d8088b91063ccaea3c970efe78 ]
HW_TAGS KASAN skips zeroing page_alloc allocations backing vmalloc
mappings via __GFP_SKIP_ZERO. Instead, these pages are zeroed via
kasan_unpoison_vmalloc() by passing the KASAN_VMALLOC_INIT flag.
The problem is that __kasan_unpoison_vmalloc() does not zero pages when
either kasan_vmalloc_enabled() or is_vmalloc_or_module_addr() fail.
Thus:
1. Change __vmalloc_node_range() to only set KASAN_VMALLOC_INIT when
__GFP_SKIP_ZERO is set.
2. Change __kasan_unpoison_vmalloc() to always zero pages when the
KASAN_VMALLOC_INIT flag is set.
3. Add WARN_ON() asserts to check that KASAN_VMALLOC_INIT cannot be set
in other early return paths of __kasan_unpoison_vmalloc().
Also clean up the comment in __kasan_unpoison_vmalloc.
Link:
https://lkml.kernel.org/r/4bc503537efdc539ffc3f461c1b70162eea31cf6.1654798516.git.andreyknvl@xxxxxxxxxx
Fixes: 23689e91fb22 ("kasan, vmalloc: add vmalloc tagging for HW_TAGS")
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
mm/kasan/hw_tags.c | 32 +++++++++++++++++++++++---------
mm/vmalloc.c | 10 +++++-----
2 files changed, 28 insertions(+), 14 deletions(-)
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 9e1b6544bfa8..9ad8eff71b28 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -257,27 +257,37 @@ static void unpoison_vmalloc_pages(const void
*addr, u8 tag)
}
}
+static void init_vmalloc_pages(const void *start, unsigned long size)
+{
+ const void *addr;
+
+ for (addr = start; addr < start + size; addr += PAGE_SIZE) {
+ struct page *page = virt_to_page(addr);
+
+ clear_highpage_kasan_tagged(page);
This breaks build on aarch64:
mm/kasan/hw_tags.c: In function 'init_vmalloc_pages':
mm/kasan/hw_tags.c:267:17: error: implicit declaration of function
'clear_highpage_kasan_tagged' [-Werror=implicit-function-declaration]
Which translates into: this is missing:
commit d9da8f6cf55eeca642c021912af1890002464c64
Author: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Date: Thu Jun 9 20:18:46 2022 +0200
mm: introduce clear_highpage_kasan_tagged
+ }
+}
+
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
kasan_vmalloc_flags_t flags)
{
u8 tag;
unsigned long redzone_start, redzone_size;
- if (!kasan_vmalloc_enabled())
- return (void *)start;
-
- if (!is_vmalloc_or_module_addr(start))
+ if (!kasan_vmalloc_enabled() || !is_vmalloc_or_module_addr(start)) {
+ if (flags & KASAN_VMALLOC_INIT)
+ init_vmalloc_pages(start, size);
return (void *)start;
+ }
/*
- * Skip unpoisoning and assigning a pointer tag for non-VM_ALLOC
- * mappings as:
+ * Don't tag non-VM_ALLOC mappings, as:
*
* 1. Unlike the software KASAN modes, hardware tag-based KASAN
only
* supports tagging physical memory. Therefore, it can only
tag a
* single mapping of normal physical pages.
* 2. Hardware tag-based KASAN can only tag memory mapped with
special
- * mapping protection bits, see arch_vmalloc_pgprot_modify().
+ * mapping protection bits, see arch_vmap_pgprot_tagged().
* As non-VM_ALLOC mappings can be mapped outside of vmalloc
code,
* providing these bits would require tracking all non-VM_ALLOC
* mappers.
@@ -289,15 +299,19 @@ void *__kasan_unpoison_vmalloc(const void
*start, unsigned long size,
*
* For non-VM_ALLOC allocations, page_alloc memory is tagged as
usual.
*/
- if (!(flags & KASAN_VMALLOC_VM_ALLOC))
+ if (!(flags & KASAN_VMALLOC_VM_ALLOC)) {
+ WARN_ON(flags & KASAN_VMALLOC_INIT);
return (void *)start;
+ }
/*
* Don't tag executable memory.
* The kernel doesn't tolerate having the PC register tagged.
*/
- if (!(flags & KASAN_VMALLOC_PROT_NORMAL))
+ if (!(flags & KASAN_VMALLOC_PROT_NORMAL)) {
+ WARN_ON(flags & KASAN_VMALLOC_INIT);
return (void *)start;
+ }
tag = kasan_random_tag();
start = set_tag(start, tag);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index effd1ff6a4b4..a1ab9b472571 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3168,15 +3168,15 @@ void *__vmalloc_node_range(unsigned long size,
unsigned long align,
/*
* Mark the pages as accessible, now that they are mapped.
- * The init condition should match the one in post_alloc_hook()
- * (except for the should_skip_init() check) to make sure that
memory
- * is initialized under the same conditions regardless of the
enabled
- * KASAN mode.
+ * The condition for setting KASAN_VMALLOC_INIT should complement
the
+ * one in post_alloc_hook() with regards to the __GFP_SKIP_ZERO
check
+ * to make sure that memory is initialized under the same
conditions.
* Tag-based KASAN modes only assign tags to normal non-executable
* allocations, see __kasan_unpoison_vmalloc().
*/
kasan_flags |= KASAN_VMALLOC_VM_ALLOC;
- if (!want_init_on_free() && want_init_on_alloc(gfp_mask))
+ if (!want_init_on_free() && want_init_on_alloc(gfp_mask) &&
+ (gfp_mask & __GFP_SKIP_ZERO))
kasan_flags |= KASAN_VMALLOC_INIT;
/* KASAN_VMALLOC_PROT_NORMAL already set if required. */
area->addr = kasan_unpoison_vmalloc(area->addr, real_size,
kasan_flags);
--
js
suse labs