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kasan, vmalloc: add vmalloc tagging for HW_TAGS

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Add vmalloc tagging support to HW_TAGS KASAN.

The key difference between HW_TAGS and the other two KASAN modes when it
comes to vmalloc: HW_TAGS KASAN can only assign tags to physical memory.
The other two modes have shadow memory covering every mapped virtual
memory region.

Make __kasan_unpoison_vmalloc() for HW_TAGS KASAN:

 - Skip non-VM_ALLOC mappings as HW_TAGS KASAN can only tag a single
   mapping of normal physical memory; see the comment in the function.

 - Generate a random tag, tag the returned pointer and the allocation,
   and initialize the allocation at the same time.

 - Propagate the tag into the page stucts to allow accesses through
   page_address(vmalloc_to_page()).

The rest of vmalloc-related KASAN hooks are not needed:

 - The shadow-related ones are fully skipped.

 - __kasan_poison_vmalloc() is kept as a no-op with a comment.

Poisoning and zeroing of physical pages that are backing vmalloc()
allocations are skipped via __GFP_SKIP_KASAN_UNPOISON and
__GFP_SKIP_ZERO: __kasan_unpoison_vmalloc() does that instead.

Enabling CONFIG_KASAN_VMALLOC with HW_TAGS is not yet allowed.

Link: https://lkml.kernel.org/r/d19b2e9e59a9abc59d05b72dea8429dcaea739c6.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2022-03-24 18:11:32 -07:00 committed by Linus Torvalds
parent 9353ffa6e9
commit 23689e91fb
5 changed files with 175 additions and 18 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

36
include/linux/kasan.h
View file

@ -26,6 +26,12 @@ struct kunit_kasan_expectation {
#endif
typedef unsigned int __bitwise kasan_vmalloc_flags_t;
#define KASAN_VMALLOC_NONE 0x00u
#define KASAN_VMALLOC_INIT 0x01u
#define KASAN_VMALLOC_VM_ALLOC 0x02u
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
#include <linux/pgtable.h>
@ -397,18 +403,39 @@ static inline void kasan_init_hw_tags(void) { }
#ifdef CONFIG_KASAN_VMALLOC
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
void kasan_populate_early_vm_area_shadow(void *start, unsigned long size);
int kasan_populate_vmalloc(unsigned long addr, unsigned long size);
void kasan_release_vmalloc(unsigned long start, unsigned long end,
unsigned long free_region_start,
unsigned long free_region_end);
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size);
#else /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
static inline void kasan_populate_early_vm_area_shadow(void *start,
unsigned long size)
{ }
static inline int kasan_populate_vmalloc(unsigned long start,
unsigned long size)
{
return 0;
}
static inline void kasan_release_vmalloc(unsigned long start,
unsigned long end,
unsigned long free_region_start,
unsigned long free_region_end) { }
#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
kasan_vmalloc_flags_t flags);
static __always_inline void *kasan_unpoison_vmalloc(const void *start,
unsigned long size)
unsigned long size,
kasan_vmalloc_flags_t flags)
{
if (kasan_enabled())
return __kasan_unpoison_vmalloc(start, size);
return __kasan_unpoison_vmalloc(start, size, flags);
return (void *)start;
}
@ -435,7 +462,8 @@ static inline void kasan_release_vmalloc(unsigned long start,
unsigned long free_region_end) { }
static inline void *kasan_unpoison_vmalloc(const void *start,
unsigned long size)
unsigned long size,
kasan_vmalloc_flags_t flags)
{
return (void *)start;
}

4
kernel/scs.c
View file

@ -32,7 +32,7 @@ static void *__scs_alloc(int node)
for (i = 0; i < NR_CACHED_SCS; i++) {
s = this_cpu_xchg(scs_cache[i], NULL);
if (s) {
kasan_unpoison_vmalloc(s, SCS_SIZE);
kasan_unpoison_vmalloc(s, SCS_SIZE, KASAN_VMALLOC_NONE);
memset(s, 0, SCS_SIZE);
return s;
}
@ -78,7 +78,7 @@ void scs_free(void *s)
if (this_cpu_cmpxchg(scs_cache[i], 0, s) == NULL)
return;
kasan_unpoison_vmalloc(s, SCS_SIZE);
kasan_unpoison_vmalloc(s, SCS_SIZE, KASAN_VMALLOC_NONE);
vfree_atomic(s);
}

92
mm/kasan/hw_tags.c
View file

@ -192,6 +192,98 @@ void __init kasan_init_hw_tags(void)
kasan_stack_collection_enabled() ? "on" : "off");
}
#ifdef CONFIG_KASAN_VMALLOC
static void unpoison_vmalloc_pages(const void *addr, u8 tag)
{
struct vm_struct *area;
int i;
/*
* As hardware tag-based KASAN only tags VM_ALLOC vmalloc allocations
* (see the comment in __kasan_unpoison_vmalloc), all of the pages
* should belong to a single area.
*/
area = find_vm_area((void *)addr);
if (WARN_ON(!area))
return;
for (i = 0; i < area->nr_pages; i++) {
struct page *page = area->pages[i];
page_kasan_tag_set(page, tag);
}
}
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
kasan_vmalloc_flags_t flags)
{
u8 tag;
unsigned long redzone_start, redzone_size;
if (!is_vmalloc_or_module_addr(start))
return (void *)start;
/*
* Skip unpoisoning and assigning a pointer tag for 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().
* As non-VM_ALLOC mappings can be mapped outside of vmalloc code,
* providing these bits would require tracking all non-VM_ALLOC
* mappers.
*
* Thus, for VM_ALLOC mappings, hardware tag-based KASAN only tags
* the first virtual mapping, which is created by vmalloc().
* Tagging the page_alloc memory backing that vmalloc() allocation is
* skipped, see ___GFP_SKIP_KASAN_UNPOISON.
*
* For non-VM_ALLOC allocations, page_alloc memory is tagged as usual.
*/
if (!(flags & KASAN_VMALLOC_VM_ALLOC))
return (void *)start;
tag = kasan_random_tag();
start = set_tag(start, tag);
/* Unpoison and initialize memory up to size. */
kasan_unpoison(start, size, flags & KASAN_VMALLOC_INIT);
/*
* Explicitly poison and initialize the in-page vmalloc() redzone.
* Unlike software KASAN modes, hardware tag-based KASAN doesn't
* unpoison memory when populating shadow for vmalloc() space.
*/
redzone_start = round_up((unsigned long)start + size,
KASAN_GRANULE_SIZE);
redzone_size = round_up(redzone_start, PAGE_SIZE) - redzone_start;
kasan_poison((void *)redzone_start, redzone_size, KASAN_TAG_INVALID,
flags & KASAN_VMALLOC_INIT);
/*
* Set per-page tag flags to allow accessing physical memory for the
* vmalloc() mapping through page_address(vmalloc_to_page()).
*/
unpoison_vmalloc_pages(start, tag);
return (void *)start;
}
void __kasan_poison_vmalloc(const void *start, unsigned long size)
{
/*
* No tagging here.
* The physical pages backing the vmalloc() allocation are poisoned
* through the usual page_alloc paths.
*/
}
#endif
#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
void kasan_enable_tagging_sync(void)

10
mm/kasan/shadow.c
View file

@ -475,8 +475,16 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
}
}
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size)
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
kasan_vmalloc_flags_t flags)
{
/*
* Software KASAN modes unpoison both VM_ALLOC and non-VM_ALLOC
* mappings, so the KASAN_VMALLOC_VM_ALLOC flag is ignored.
* Software KASAN modes can't optimize zeroing memory by combining it
* with setting memory tags, so the KASAN_VMALLOC_INIT flag is ignored.
*/
if (!is_vmalloc_or_module_addr(start))
return (void *)start;

51
mm/vmalloc.c
View file

@ -2237,8 +2237,12 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
return NULL;
}
/* Mark the pages as accessible, now that they are mapped. */
mem = kasan_unpoison_vmalloc(mem, size);
/*
* Mark the pages as accessible, now that they are mapped.
* 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);
return mem;
}
@ -2472,9 +2476,12 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
* best-effort approach, as they can be mapped outside of vmalloc code.
* For VM_ALLOC mappings, the pages are marked as accessible after
* getting mapped in __vmalloc_node_range().
* With hardware tag-based KASAN, marking is skipped for
* non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().
*/
if (!(flags & VM_ALLOC))
area->addr = kasan_unpoison_vmalloc(area->addr, requested_size);
area->addr = kasan_unpoison_vmalloc(area->addr, requested_size,
KASAN_VMALLOC_NONE);
return area;
}
@ -3084,6 +3091,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
{
struct vm_struct *area;
void *ret;
kasan_vmalloc_flags_t kasan_flags;
unsigned long real_size = size;
unsigned long real_align = align;
unsigned int shift = PAGE_SHIFT;
@ -3136,21 +3144,39 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
goto fail;
}
/*
* Modify protection bits to allow tagging.
* This must be done before mapping by __vmalloc_area_node().
*/
/* Prepare arguments for __vmalloc_area_node(). */
if (kasan_hw_tags_enabled() &&
pgprot_val(prot) == pgprot_val(PAGE_KERNEL))
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);
/*
* 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;
}
/* Allocate physical pages and map them into vmalloc space. */
ret = __vmalloc_area_node(area, gfp_mask, prot, shift, node);
if (!ret)
goto fail;
/* Mark the pages as accessible, now that they are mapped. */
area->addr = kasan_unpoison_vmalloc(area->addr, real_size);
/*
* 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.
*/
kasan_flags = KASAN_VMALLOC_VM_ALLOC;
if (!want_init_on_free() && want_init_on_alloc(gfp_mask))
kasan_flags |= KASAN_VMALLOC_INIT;
area->addr = kasan_unpoison_vmalloc(area->addr, real_size, kasan_flags);
/*
* In this function, newly allocated vm_struct has VM_UNINITIALIZED
@ -3850,10 +3876,13 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
/*
* Mark allocated areas as accessible. Do it now as a best-effort
* approach, as they can be mapped outside of vmalloc code.
* With hardware tag-based KASAN, marking is skipped for
* non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().
*/
for (area = 0; area < nr_vms; area++)
vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
vms[area]->size);
vms[area]->size,
KASAN_VMALLOC_NONE);
kfree(vas);
return vms;