From: andrey.konovalov@linux.dev
To: Marco Elver <elver@google.com>,
Alexander Potapenko <glider@google.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
kasan-dev@googlegroups.com, linux-mm@kvack.org,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
linux-arm-kernel@lists.infradead.org,
Peter Collingbourne <pcc@google.com>,
Evgenii Stepanov <eugenis@google.com>,
linux-kernel@vger.kernel.org,
Andrey Konovalov <andreyknvl@google.com>
Subject: [PATCH mm v4 31/39] kasan, vmalloc: only tag normal vmalloc allocations
Date: Mon, 20 Dec 2021 23:02:03 +0100 [thread overview]
Message-ID: <09fc776d03e8aaa9efa78c743392972060f5256d.1640036051.git.andreyknvl@google.com> (raw)
In-Reply-To: <cover.1640036051.git.andreyknvl@google.com>
From: Andrey Konovalov <andreyknvl@google.com>
The kernel can use to allocate executable memory. The only supported way
to do that is via __vmalloc_node_range() with the executable bit set in
the prot argument. (vmap() resets the bit via pgprot_nx()).
Once tag-based KASAN modes start tagging vmalloc allocations, executing
code from such allocations will lead to the PC register getting a tag,
which is not tolerated by the kernel.
Only tag the allocations for normal kernel pages.
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
Changes v3->v4:
- Rename KASAN_VMALLOC_NOEXEC to KASAN_VMALLOC_PROT_NORMAL.
- Compare with PAGE_KERNEL instead of using pgprot_nx().
- Update patch description.
Changes v2->v3:
- Add this patch.
---
include/linux/kasan.h | 7 ++++---
mm/kasan/hw_tags.c | 7 +++++++
mm/kasan/shadow.c | 7 +++++++
mm/vmalloc.c | 49 +++++++++++++++++++++++++------------------
4 files changed, 47 insertions(+), 23 deletions(-)
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 499f1573dba4..3593c95d1fa5 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -27,9 +27,10 @@ struct kunit_kasan_expectation {
typedef unsigned int __bitwise kasan_vmalloc_flags_t;
-#define KASAN_VMALLOC_NONE 0x00u
-#define KASAN_VMALLOC_INIT 0x01u
-#define KASAN_VMALLOC_VM_ALLOC 0x02u
+#define KASAN_VMALLOC_NONE 0x00u
+#define KASAN_VMALLOC_INIT 0x01u
+#define KASAN_VMALLOC_VM_ALLOC 0x02u
+#define KASAN_VMALLOC_PROT_NORMAL 0x04u
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 21104fd51872..2e9378a4f07f 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -247,6 +247,13 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
if (!(flags & KASAN_VMALLOC_VM_ALLOC))
return (void *)start;
+ /*
+ * Don't tag executable memory.
+ * The kernel doesn't tolerate having the PC register tagged.
+ */
+ if (!(flags & KASAN_VMALLOC_PROT_NORMAL))
+ return (void *)start;
+
tag = kasan_random_tag();
start = set_tag(start, tag);
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index b958babc8fed..7272e248db87 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -488,6 +488,13 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
if (!is_vmalloc_or_module_addr(start))
return (void *)start;
+ /*
+ * Don't tag executable memory.
+ * The kernel doesn't tolerate having the PC register tagged.
+ */
+ if (!(flags & KASAN_VMALLOC_PROT_NORMAL))
+ return (void *)start;
+
start = set_tag(start, kasan_random_tag());
kasan_unpoison(start, size, false);
return (void *)start;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 47f3de7a3396..01ec2ef447af 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2220,7 +2220,7 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
* With hardware tag-based KASAN, marking is skipped for
* non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().
*/
- mem = kasan_unpoison_vmalloc(mem, size, KASAN_VMALLOC_NONE);
+ mem = kasan_unpoison_vmalloc(mem, size, KASAN_VMALLOC_PROT_NORMAL);
return mem;
}
@@ -2459,7 +2459,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
*/
if (!(flags & VM_ALLOC))
area->addr = kasan_unpoison_vmalloc(area->addr, requested_size,
- KASAN_VMALLOC_NONE);
+ KASAN_VMALLOC_PROT_NORMAL);
return area;
}
@@ -3065,7 +3065,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
{
struct vm_struct *area;
void *ret;
- kasan_vmalloc_flags_t kasan_flags;
+ kasan_vmalloc_flags_t kasan_flags = KASAN_VMALLOC_NONE;
unsigned long real_size = size;
unsigned long real_align = align;
unsigned int shift = PAGE_SHIFT;
@@ -3118,21 +3118,28 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
goto fail;
}
- /* Prepare arguments for __vmalloc_area_node(). */
- if (kasan_hw_tags_enabled() &&
- pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) {
- /*
- * Modify protection bits to allow tagging.
- * This must be done before mapping in __vmalloc_area_node().
- */
- prot = arch_vmap_pgprot_tagged(prot);
+ /*
+ * Prepare arguments for __vmalloc_area_node() and
+ * kasan_unpoison_vmalloc().
+ */
+ if (pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) {
+ if (kasan_hw_tags_enabled()) {
+ /*
+ * Modify protection bits to allow tagging.
+ * This must be done before mapping.
+ */
+ prot = arch_vmap_pgprot_tagged(prot);
- /*
- * Skip page_alloc poisoning and zeroing for physical pages
- * backing VM_ALLOC mapping. Memory is instead poisoned and
- * zeroed by kasan_unpoison_vmalloc().
- */
- gfp_mask |= __GFP_SKIP_KASAN_UNPOISON | __GFP_SKIP_ZERO;
+ /*
+ * Skip page_alloc poisoning and zeroing for physical
+ * pages backing VM_ALLOC mapping. Memory is instead
+ * poisoned and zeroed by kasan_unpoison_vmalloc().
+ */
+ gfp_mask |= __GFP_SKIP_KASAN_UNPOISON | __GFP_SKIP_ZERO;
+ }
+
+ /* Take note that the mapping is PAGE_KERNEL. */
+ kasan_flags |= KASAN_VMALLOC_PROT_NORMAL;
}
/* Allocate physical pages and map them into vmalloc space. */
@@ -3146,10 +3153,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
* (except for the should_skip_init() check) to make sure that memory
* is initialized under the same conditions regardless of the enabled
* KASAN mode.
+ * Tag-based KASAN modes only assign tags to normal non-executable
+ * allocations, see __kasan_unpoison_vmalloc().
*/
- kasan_flags = KASAN_VMALLOC_VM_ALLOC;
+ kasan_flags |= KASAN_VMALLOC_VM_ALLOC;
if (!want_init_on_free() && want_init_on_alloc(gfp_mask))
kasan_flags |= KASAN_VMALLOC_INIT;
+ /* KASAN_VMALLOC_PROT_NORMAL already set if required. */
area->addr = kasan_unpoison_vmalloc(area->addr, real_size, kasan_flags);
/*
@@ -3863,8 +3873,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
*/
for (area = 0; area < nr_vms; area++)
vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
- vms[area]->size,
- KASAN_VMALLOC_NONE);
+ vms[area]->size, KASAN_VMALLOC_PROT_NORMAL);
kfree(vas);
return vms;
--
2.25.1
next prev parent reply other threads:[~2021-12-20 22:02 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 21:58 [PATCH mm v4 00/39] kasan, vmalloc, arm64: add vmalloc tagging support for SW/HW_TAGS andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 01/39] kasan, page_alloc: deduplicate should_skip_kasan_poison andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 02/39] kasan, page_alloc: move tag_clear_highpage out of kernel_init_free_pages andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 03/39] kasan, page_alloc: merge kasan_free_pages into free_pages_prepare andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 04/39] kasan, page_alloc: simplify kasan_poison_pages call site andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 05/39] kasan, page_alloc: init memory of skipped pages on free andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 06/39] kasan: drop skip_kasan_poison variable in free_pages_prepare andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 07/39] mm: clarify __GFP_ZEROTAGS comment andrey.konovalov
2021-12-21 9:16 ` Alexander Potapenko
2021-12-30 19:11 ` Andrey Konovalov
2021-12-20 21:58 ` [PATCH mm v4 08/39] kasan: only apply __GFP_ZEROTAGS when memory is zeroed andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 09/39] kasan, page_alloc: refactor init checks in post_alloc_hook andrey.konovalov
2021-12-20 21:58 ` [PATCH mm v4 10/39] kasan, page_alloc: merge kasan_alloc_pages into post_alloc_hook andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 11/39] kasan, page_alloc: combine tag_clear_highpage calls in post_alloc_hook andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 12/39] kasan, page_alloc: move SetPageSkipKASanPoison " andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 13/39] kasan, page_alloc: move kernel_init_free_pages " andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 14/39] kasan, page_alloc: rework kasan_unpoison_pages call site andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 15/39] kasan: clean up metadata byte definitions andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 16/39] kasan: define KASAN_VMALLOC_INVALID for SW_TAGS andrey.konovalov
2021-12-21 9:23 ` Alexander Potapenko
2021-12-20 21:59 ` [PATCH mm v4 17/39] kasan, x86, arm64, s390: rename functions for modules shadow andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 18/39] kasan, vmalloc: drop outdated VM_KASAN comment andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 19/39] kasan: reorder vmalloc hooks andrey.konovalov
2021-12-20 21:59 ` [PATCH mm v4 20/39] kasan: add wrappers for " andrey.konovalov
2021-12-21 14:21 ` Alexander Potapenko
2021-12-20 21:59 ` [PATCH mm v4 21/39] kasan, vmalloc: reset tags in vmalloc functions andrey.konovalov
2021-12-20 22:01 ` [PATCH mm v4 22/39] kasan, fork: reset pointer tags of vmapped stacks andrey.konovalov
2021-12-21 15:11 ` Alexander Potapenko
2021-12-20 22:01 ` [PATCH mm v4 23/39] kasan, arm64: " andrey.konovalov
2021-12-20 22:01 ` [PATCH mm v4 24/39] kasan, vmalloc: add vmalloc tagging for SW_TAGS andrey.konovalov
2021-12-20 22:01 ` [PATCH mm v4 25/39] kasan, vmalloc, arm64: mark vmalloc mappings as pgprot_tagged andrey.konovalov
2021-12-20 22:01 ` [PATCH mm v4 26/39] kasan, vmalloc: unpoison VM_ALLOC pages after mapping andrey.konovalov
2021-12-21 11:50 ` Alexander Potapenko
2021-12-20 22:01 ` [PATCH mm v4 27/39] kasan, mm: only define ___GFP_SKIP_KASAN_POISON with HW_TAGS andrey.konovalov
2021-12-20 22:02 ` [PATCH mm v4 28/39] kasan, page_alloc: allow skipping unpoisoning for HW_TAGS andrey.konovalov
2021-12-21 12:04 ` Marco Elver
2021-12-30 19:11 ` Andrey Konovalov
2021-12-21 12:14 ` Marco Elver
2021-12-21 12:19 ` Marco Elver
2021-12-20 22:02 ` [PATCH mm v4 29/39] kasan, page_alloc: allow skipping memory init " andrey.konovalov
2021-12-21 12:11 ` Marco Elver
2021-12-30 19:11 ` Andrey Konovalov
2021-12-21 12:30 ` Marco Elver
2021-12-30 19:11 ` Andrey Konovalov
2021-12-20 22:02 ` [PATCH mm v4 30/39] kasan, vmalloc: add vmalloc tagging " andrey.konovalov
2021-12-20 22:02 ` andrey.konovalov [this message]
2021-12-20 22:02 ` [PATCH mm v4 32/39] kasan, arm64: don't tag executable vmalloc allocations andrey.konovalov
2021-12-20 22:05 ` Andrey Konovalov
2021-12-22 11:11 ` Catalin Marinas
2021-12-20 22:02 ` [PATCH mm v4 33/39] kasan: mark kasan_arg_stacktrace as __initdata andrey.konovalov
2021-12-20 22:02 ` [PATCH mm v4 34/39] kasan: simplify kasan_init_hw_tags andrey.konovalov
2021-12-20 22:02 ` [PATCH mm v4 35/39] kasan: add kasan.vmalloc command line flag andrey.konovalov
2021-12-21 14:43 ` Alexander Potapenko
2021-12-30 19:11 ` Andrey Konovalov
2021-12-20 22:03 ` [PATCH mm v4 36/39] kasan: allow enabling KASAN_VMALLOC and SW/HW_TAGS andrey.konovalov
2021-12-20 22:03 ` [PATCH mm v4 37/39] arm64: select KASAN_VMALLOC for SW/HW_TAGS modes andrey.konovalov
2021-12-20 22:03 ` [PATCH mm v4 38/39] kasan: documentation updates andrey.konovalov
2021-12-20 22:03 ` [PATCH mm v4 39/39] kasan: improve vmalloc tests andrey.konovalov
2021-12-22 7:00 ` [PATCH mm v4 00/39] kasan, vmalloc, arm64: add vmalloc tagging support for SW/HW_TAGS Marco Elver
2021-12-30 19:11 ` Andrey Konovalov
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