The patch titled
Subject: kasan, page_alloc: allow skipping unpoisoning for HW_TAGS
has been added to the -mm tree. Its filename is
kasan-page_alloc-allow-skipping-unpoisoning-for-hw_tags.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kasan-page_alloc-allow-skipping-unpoisoning-for-hw_tags.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kasan-page_alloc-allow-skipping-unpoisoning-for-hw_tags.patch
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------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: kasan, page_alloc: allow skipping unpoisoning for HW_TAGS
Add a new GFP flag __GFP_SKIP_KASAN_UNPOISON that allows skipping KASAN
poisoning for page_alloc allocations. The flag is only effective with
HW_TAGS KASAN.
This flag will be used by vmalloc code for page_alloc allocations backing
vmalloc() mappings in a following patch. The reason to skip KASAN
poisoning for these pages in page_alloc is because vmalloc code will be
poisoning them instead.
Also reword the comment for __GFP_SKIP_KASAN_POISON.
Link: https://lkml.kernel.org/r/35c97d77a704f6ff971dd3bfe4be95855744108e.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/gfp.h | 21 +++++++++++++--------
include/trace/events/mmflags.h | 5 +++--
mm/page_alloc.c | 31 ++++++++++++++++++++++---------
3 files changed, 38 insertions(+), 19 deletions(-)
--- a/include/linux/gfp.h~kasan-page_alloc-allow-skipping-unpoisoning-for-hw_tags
+++ a/include/linux/gfp.h
@@ -55,12 +55,14 @@ struct vm_area_struct;
#define ___GFP_ACCOUNT 0x400000u
#define ___GFP_ZEROTAGS 0x800000u
#ifdef CONFIG_KASAN_HW_TAGS
-#define ___GFP_SKIP_KASAN_POISON 0x1000000u
+#define ___GFP_SKIP_KASAN_UNPOISON 0x1000000u
+#define ___GFP_SKIP_KASAN_POISON 0x2000000u
#else
+#define ___GFP_SKIP_KASAN_UNPOISON 0
#define ___GFP_SKIP_KASAN_POISON 0
#endif
#ifdef CONFIG_LOCKDEP
-#define ___GFP_NOLOCKDEP 0x2000000u
+#define ___GFP_NOLOCKDEP 0x4000000u
#else
#define ___GFP_NOLOCKDEP 0
#endif
@@ -241,22 +243,25 @@ struct vm_area_struct;
* intended for optimization: setting memory tags at the same time as zeroing
* memory has minimal additional performace impact.
*
- * %__GFP_SKIP_KASAN_POISON returns a page which does not need to be poisoned
- * on deallocation. Typically used for userspace pages. Currently only has an
- * effect in HW tags mode.
+ * %__GFP_SKIP_KASAN_UNPOISON makes KASAN skip unpoisoning on page allocation.
+ * Only effective in HW_TAGS mode.
+ *
+ * %__GFP_SKIP_KASAN_POISON makes KASAN skip poisoning on page deallocation.
+ * Typically, used for userspace pages. Only effective in HW_TAGS mode.
*/
#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN)
#define __GFP_COMP ((__force gfp_t)___GFP_COMP)
#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO)
#define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS)
-#define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON)
+#define __GFP_SKIP_KASAN_UNPOISON ((__force gfp_t)___GFP_SKIP_KASAN_UNPOISON)
+#define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON)
/* Disable lockdep for GFP context tracking */
#define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
/* Room for N __GFP_FOO bits */
-#define __GFP_BITS_SHIFT (24 + \
- IS_ENABLED(CONFIG_KASAN_HW_TAGS) + \
+#define __GFP_BITS_SHIFT (24 + \
+ 2 * IS_ENABLED(CONFIG_KASAN_HW_TAGS) + \
IS_ENABLED(CONFIG_LOCKDEP))
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
--- a/include/trace/events/mmflags.h~kasan-page_alloc-allow-skipping-unpoisoning-for-hw_tags
+++ a/include/trace/events/mmflags.h
@@ -52,8 +52,9 @@
{(unsigned long)__GFP_ZEROTAGS, "__GFP_ZEROTAGS"} \
#ifdef CONFIG_KASAN_HW_TAGS
-#define __def_gfpflag_names_kasan \
- , {(unsigned long)__GFP_SKIP_KASAN_POISON, "__GFP_SKIP_KASAN_POISON"}
+#define __def_gfpflag_names_kasan , \
+ {(unsigned long)__GFP_SKIP_KASAN_POISON, "__GFP_SKIP_KASAN_POISON"}, \
+ {(unsigned long)__GFP_SKIP_KASAN_UNPOISON, "__GFP_SKIP_KASAN_UNPOISON"}
#else
#define __def_gfpflag_names_kasan
#endif
--- a/mm/page_alloc.c~kasan-page_alloc-allow-skipping-unpoisoning-for-hw_tags
+++ a/mm/page_alloc.c
@@ -2395,6 +2395,26 @@ static bool check_new_pages(struct page
return false;
}
+static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
+{
+ /* Don't skip if a software KASAN mode is enabled. */
+ if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
+ IS_ENABLED(CONFIG_KASAN_SW_TAGS))
+ return false;
+
+ /* Skip, if hardware tag-based KASAN is not enabled. */
+ if (!kasan_hw_tags_enabled())
+ return true;
+
+ /*
+ * With hardware tag-based KASAN enabled, skip if either:
+ *
+ * 1. Memory tags have already been cleared via tag_clear_highpage().
+ * 2. Skipping has been requested via __GFP_SKIP_KASAN_UNPOISON.
+ */
+ return init_tags || (flags & __GFP_SKIP_KASAN_UNPOISON);
+}
+
inline void post_alloc_hook(struct page *page, unsigned int order,
gfp_t gfp_flags)
{
@@ -2434,15 +2454,8 @@ inline void post_alloc_hook(struct page
/* Note that memory is already initialized by the loop above. */
init = false;
}
- /*
- * If either a software KASAN mode is enabled, or,
- * in the case of hardware tag-based KASAN,
- * if memory tags have not been cleared via tag_clear_highpage().
- */
- if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
- IS_ENABLED(CONFIG_KASAN_SW_TAGS) ||
- kasan_hw_tags_enabled() && !init_tags) {
- /* Mark shadow memory or set memory tags. */
+ if (!should_skip_kasan_unpoison(gfp_flags, init_tags)) {
+ /* Unpoison shadow memory or set memory tags. */
kasan_unpoison_pages(page, order, init);
/* Note that memory is already initialized by KASAN. */
_
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
