[PATCH 1/3] mm: rename kernel_init_free_pages to kernel_init_pages

[andrey.k...@linux.dev]

From: Andrey Konovalov <andre...@google.com>

Rename kernel_init_free_pages() to kernel_init_pages(). This function is
not only used for free pages but also for pages that were just allocated.

Signed-off-by: Andrey Konovalov <andre...@google.com>
---
mm/page_alloc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e008a3df0485..66ef8c310dce 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1296,7 +1296,7 @@ static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
PageSkipKASanPoison(page);
}

-static void kernel_init_free_pages(struct page *page, int numpages)
+static void kernel_init_pages(struct page *page, int numpages)
{
int i;

@@ -1396,7 +1396,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
init = false;
}
if (init)
- kernel_init_free_pages(page, 1 << order);
+ kernel_init_pages(page, 1 << order);

/*
* arch_free_page() can make the page's contents inaccessible. s390
@@ -2441,7 +2441,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
}
/* If memory is still not initialized, do it now. */
if (init)
- kernel_init_free_pages(page, 1 << order);
+ kernel_init_pages(page, 1 << order);
/* Propagate __GFP_SKIP_KASAN_POISON to page flags. */
if (kasan_hw_tags_enabled() && (gfp_flags & __GFP_SKIP_KASAN_POISON))
SetPageSkipKASanPoison(page);
--
2.25.1

[andrey.k...@linux.dev]

From: Andrey Konovalov <andre...@google.com>

Add a clear_highpage_tagged() helper that does clear_highpage() on a
page potentially tagged by KASAN.

This helper is used by the following patch.

Signed-off-by: Andrey Konovalov <andre...@google.com>
---

include/linux/highmem.h | 11 +++++++++++
mm/page_alloc.c | 8 ++------
2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 3af34de54330..df76a0db7cec 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -243,6 +243,17 @@ static inline void clear_highpage(struct page *page)
kunmap_local(kaddr);
}

+static inline void clear_highpage_tagged(struct page *page)
+{
+ u8 tag;
+
+ tag = page_kasan_tag(page);
+ page_kasan_tag_reset(page);
+ clear_highpage(page);
+ page_kasan_tag_set(page, tag);
+
+}
+
#ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE

static inline void tag_clear_highpage(struct page *page)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 66ef8c310dce..d82ea983a7a3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1302,12 +1302,8 @@ static void kernel_init_pages(struct page *page, int numpages)

/* s390's use of memset() could override KASAN redzones. */
kasan_disable_current();
- for (i = 0; i < numpages; i++) {
- u8 tag = page_kasan_tag(page + i);
- page_kasan_tag_reset(page + i);
- clear_highpage(page + i);
- page_kasan_tag_set(page + i, tag);
- }
+ for (i = 0; i < numpages; i++)
+ clear_highpage_tagged(page + i);
kasan_enable_current();
}

--
2.25.1

[andrey.k...@linux.dev]

From: Andrey Konovalov <andre...@google.com>

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.

Fixes: 23689e91fb22 ("kasan, vmalloc: add vmalloc tagging for HW_TAGS")

Signed-off-by: Andrey Konovalov <andre...@google.com>
---

mm/kasan/hw_tags.c | 30 ++++++++++++++++++++++--------
mm/vmalloc.c | 10 +++++-----
2 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 9e1b6544bfa8..c0ec01eadf20 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -263,21 +263,31 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
u8 tag;
unsigned long redzone_start, redzone_size;

- if (!kasan_vmalloc_enabled())
- return (void *)start;
+ if (!kasan_vmalloc_enabled() || !is_vmalloc_or_module_addr(start)) {
+ struct page *page;
+ const void *addr;
+
+ /* Initialize memory if required. */
+
+ if (!(flags & KASAN_VMALLOC_INIT))
+ return (void *)start;
+
+ for (addr = start; addr < start + size; addr += PAGE_SIZE) {
+ page = virt_to_page(addr);
+ clear_highpage_tagged(page);
+ }

- if (!is_vmalloc_or_module_addr(start))
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 07db42455dd4..0adf4aa1514d 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);
--
2.25.1

[Andrew Morton]

On Tue, 31 May 2022 17:43:49 +0200 andrey.k...@linux.dev wrote:

> From: Andrey Konovalov <andre...@google.com>
>
> Add a clear_highpage_tagged() helper that does clear_highpage() on a
> page potentially tagged by KASAN.

clear_highpage_kasan_tagged() would be a better name, no?

--- a/include/linux/highmem.h~mm-introduce-clear_highpage_tagged-fix
+++ a/include/linux/highmem.h
@@ -243,7 +243,7 @@ static inline void clear_highpage(struct
kunmap_local(kaddr);
}

-static inline void clear_highpage_tagged(struct page *page)
+static inline void clear_highpage_kasan_tagged(struct page *page)
{
u8 tag;

--- a/mm/page_alloc.c~mm-introduce-clear_highpage_tagged-fix
+++ a/mm/page_alloc.c
@@ -1311,7 +1311,7 @@ static void kernel_init_pages(struct pag

/* s390's use of memset() could override KASAN redzones. */
kasan_disable_current();

for (i = 0; i < numpages; i++)

- clear_highpage_tagged(page + i);
+ clear_highpage_kasan_tagged(page + i);
kasan_enable_current();
}

_

[Andrey Konovalov]

On Tue, May 31, 2022 at 7:52 PM Andrew Morton <ak...@linux-foundation.org> wrote:
>
> On Tue, 31 May 2022 17:43:49 +0200 andrey.k...@linux.dev wrote:
>
> > From: Andrey Konovalov <andre...@google.com>
> >
> > Add a clear_highpage_tagged() helper that does clear_highpage() on a
> > page potentially tagged by KASAN.
>
> clear_highpage_kasan_tagged() would be a better name, no?

Sounds good! Will include into v2.

I also noticed there's an extra empty line at the end of the function
I need to fix.

[Marco Elver]

This whole block of code looks out-of-place in this function, since it's
not at all related to unpoisoning but a fallback if KASAN-vmalloc is off
but we still want to initialize the memory.

Maybe to ease readability here I'd change it to look like:


diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 11f661a2494b..227c20d09258 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -257,6 +257,21 @@ static void unpoison_vmalloc_pages(const void *addr, u8 tag)
}
}

+/*
+ * Explicit initialization of pages if KASAN does not handle VM_ALLOC
+ * allocations.
+ */
+static void init_vmalloc_pages_explicit(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);
+ }
+}
+

void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,

kasan_vmalloc_flags_t flags)
{
@@ -264,19 +279,8 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
unsigned long redzone_start, redzone_size;

if (!kasan_vmalloc_enabled() || !is_vmalloc_or_module_addr(start)) {
- struct page *page;
- const void *addr;
-
- /* Initialize memory if required. */
-
- if (!(flags & KASAN_VMALLOC_INIT))
- return (void *)start;
-
- for (addr = start; addr < start + size; addr += PAGE_SIZE) {
- page = virt_to_page(addr);
- clear_highpage_kasan_tagged(page);
- }
-
+ if (flags & KASAN_VMALLOC_INIT)
+ init_vmalloc_pages_explicit(start, size);
return (void *)start;
}

[Andrey Konovalov]

Sounds good, will do in v2! Thanks!

[andrey.k...@linux.dev]

From: Andrey Konovalov <andre...@google.com>

Rename kernel_init_free_pages() to kernel_init_pages(). This function is
not only used for free pages but also for pages that were just allocated.

Signed-off-by: Andrey Konovalov <andre...@google.com>
---

mm/page_alloc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e008a3df0485..66ef8c310dce 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

[andrey.k...@linux.dev]

From: Andrey Konovalov <andre...@google.com>

Add a clear_highpage_kasan_tagged() helper that does clear_highpage()

on a page potentially tagged by KASAN.

This helper is used by the following patch.

Signed-off-by: Andrey Konovalov <andre...@google.com>

---

Changes v1->v2:
- Renamed clear_highpage_tagged() to clear_highpage_kasan_tagged().
- Removed extra empty line in clear_highpage_kasan_tagged().
---
include/linux/highmem.h | 10 ++++++++++
mm/page_alloc.c | 8 ++------
2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 3af34de54330..70b496bbd2d9 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -243,6 +243,16 @@ static inline void clear_highpage(struct page *page)
kunmap_local(kaddr);

}

+static inline void clear_highpage_kasan_tagged(struct page *page)

+{
+ u8 tag;
+
+ tag = page_kasan_tag(page);
+ page_kasan_tag_reset(page);
+ clear_highpage(page);
+ page_kasan_tag_set(page, tag);
+}
+

#ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE

static inline void tag_clear_highpage(struct page *page)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 66ef8c310dce..76a02255f57c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1302,12 +1302,8 @@ static void kernel_init_pages(struct page *page, int numpages)

/* s390's use of memset() could override KASAN redzones. */
kasan_disable_current();

- for (i = 0; i < numpages; i++) {
- u8 tag = page_kasan_tag(page + i);
- page_kasan_tag_reset(page + i);
- clear_highpage(page + i);
- page_kasan_tag_set(page + i, tag);
- }

+ for (i = 0; i < numpages; i++)

+ clear_highpage_kasan_tagged(page + i);
kasan_enable_current();
}

--
2.25.1

[andrey.k...@linux.dev]

From: Andrey Konovalov <andre...@google.com>

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.

Fixes: 23689e91fb22 ("kasan, vmalloc: add vmalloc tagging for HW_TAGS")

Signed-off-by: Andrey Konovalov <andre...@google.com>

---

Changes v1->v2:
- Add init_vmalloc_pages() helper.
---
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);
+ }
+}
+

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);

[Muchun Song]

On Thu, Jun 09, 2022 at 08:18:45PM +0200, andrey.k...@linux.dev wrote:
> From: Andrey Konovalov <andre...@google.com>
>
> Rename kernel_init_free_pages() to kernel_init_pages(). This function is
> not only used for free pages but also for pages that were just allocated.
>
> Signed-off-by: Andrey Konovalov <andre...@google.com>

LGTM.

Reviewed-by: Muchun Song <songm...@bytedance.com>

Thanks.

[Andrew Morton]

On Thu, 9 Jun 2022 20:18:45 +0200 andrey.k...@linux.dev wrote:

> From: Andrey Konovalov <andre...@google.com>
>
> Rename kernel_init_free_pages() to kernel_init_pages(). This function is
> not only used for free pages but also for pages that were just allocated.
>

Not a lot of review on these three patches. I'll plan to take silence
as assent and shall move these into the mm-stable branch a few days
hence.