The patch titled
Subject: kasan, vmalloc: only tag normal vmalloc allocations
has been added to the -mm tree. Its filename is
kasan-vmalloc-only-tag-normal-vmalloc-allocations.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kasan-vmalloc-only-tag-normal-vmalloc-allocations.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kasan-vmalloc-only-tag-normal-vmalloc-allocations.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: kasan, vmalloc: only tag normal vmalloc allocations
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.
Link: https://lkml.kernel.org/r/fbfd9939a4dc375923c9a5c6b9e7ab05c26b8c6b.1643047180.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Acked-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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(-)
--- a/include/linux/kasan.h~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/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)
--- a/mm/kasan/hw_tags.c~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/mm/kasan/hw_tags.c
@@ -247,6 +247,13 @@ void *__kasan_unpoison_vmalloc(const voi
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);
--- a/mm/kasan/shadow.c~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/mm/kasan/shadow.c
@@ -488,6 +488,13 @@ void *__kasan_unpoison_vmalloc(const voi
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;
--- a/mm/vmalloc.c~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/mm/vmalloc.c
@@ -2221,7 +2221,7 @@ void *vm_map_ram(struct page **pages, un
* 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;
}
@@ -2460,7 +2460,7 @@ static struct vm_struct *__get_vm_area_n
*/
if (!(flags & VM_ALLOC))
area->addr = kasan_unpoison_vmalloc(area->addr, requested_size,
- KASAN_VMALLOC_NONE);
+ KASAN_VMALLOC_PROT_NORMAL);
return area;
}
@@ -3071,7 +3071,7 @@ void *__vmalloc_node_range(unsigned long
{
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;
@@ -3124,21 +3124,28 @@ again:
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. */
@@ -3152,10 +3159,13 @@ again:
* (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);
/*
@@ -3861,8 +3871,7 @@ retry:
*/
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;
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
kasan-page_alloc-deduplicate-should_skip_kasan_poison.patch
kasan-page_alloc-move-tag_clear_highpage-out-of-kernel_init_free_pages.patch
kasan-page_alloc-merge-kasan_free_pages-into-free_pages_prepare.patch
kasan-page_alloc-simplify-kasan_poison_pages-call-site.patch
kasan-page_alloc-init-memory-of-skipped-pages-on-free.patch
kasan-drop-skip_kasan_poison-variable-in-free_pages_prepare.patch
mm-clarify-__gfp_zerotags-comment.patch
kasan-only-apply-__gfp_zerotags-when-memory-is-zeroed.patch
kasan-page_alloc-refactor-init-checks-in-post_alloc_hook.patch
kasan-page_alloc-merge-kasan_alloc_pages-into-post_alloc_hook.patch
kasan-page_alloc-combine-tag_clear_highpage-calls-in-post_alloc_hook.patch
kasan-page_alloc-move-setpageskipkasanpoison-in-post_alloc_hook.patch
kasan-page_alloc-move-kernel_init_free_pages-in-post_alloc_hook.patch
kasan-page_alloc-rework-kasan_unpoison_pages-call-site.patch
kasan-clean-up-metadata-byte-definitions.patch
kasan-define-kasan_vmalloc_invalid-for-sw_tags.patch
kasan-x86-arm64-s390-rename-functions-for-modules-shadow.patch
kasan-vmalloc-drop-outdated-vm_kasan-comment.patch
kasan-reorder-vmalloc-hooks.patch
kasan-add-wrappers-for-vmalloc-hooks.patch
kasan-vmalloc-reset-tags-in-vmalloc-functions.patch
kasan-fork-reset-pointer-tags-of-vmapped-stacks.patch
kasan-arm64-reset-pointer-tags-of-vmapped-stacks.patch
kasan-vmalloc-add-vmalloc-tagging-for-sw_tags.patch
kasan-vmalloc-arm64-mark-vmalloc-mappings-as-pgprot_tagged.patch
kasan-vmalloc-unpoison-vm_alloc-pages-after-mapping.patch
kasan-mm-only-define-___gfp_skip_kasan_poison-with-hw_tags.patch
kasan-page_alloc-allow-skipping-unpoisoning-for-hw_tags.patch
kasan-page_alloc-allow-skipping-memory-init-for-hw_tags.patch
kasan-vmalloc-add-vmalloc-tagging-for-hw_tags.patch
kasan-vmalloc-only-tag-normal-vmalloc-allocations.patch
kasan-arm64-dont-tag-executable-vmalloc-allocations.patch
kasan-mark-kasan_arg_stacktrace-as-__initdata.patch
kasan-clean-up-feature-flags-for-hw_tags-mode.patch
kasan-add-kasanvmalloc-command-line-flag.patch
kasan-allow-enabling-kasan_vmalloc-and-sw-hw_tags.patch
arm64-select-kasan_vmalloc-for-sw-hw_tags-modes.patch
kasan-documentation-updates.patch
kasan-improve-vmalloc-tests.patch
