diff mbox series

[11/19] kasan, mm: fix resetting page_alloc tags for HW_TAGS

Message ID 20210124050143.UF-3I8lr9%akpm@linux-foundation.org (mailing list archive)
State New, archived
Headers show
Series [01/19] x86/setup: don't remove E820_TYPE_RAM for pfn 0 | expand

Commit Message

Andrew Morton Jan. 24, 2021, 5:01 a.m. UTC 
From: Andrey Konovalov <andreyknvl@google.com>
Subject: kasan, mm: fix resetting page_alloc tags for HW_TAGS

A previous commit added resetting KASAN page tags to
kernel_init_free_pages() to avoid false-positives due to accesses to
metadata with the hardware tag-based mode.

That commit did reset page tags before the metadata access, but didn't
restore them after.  As the result, KASAN fails to detect bad accesses to
page_alloc allocations on some configurations.

Fix this by recovering the tag after the metadata access.

Link: https://lkml.kernel.org/r/02b5bcd692e912c27d484030f666b350ad7e4ae4.1611074450.git.andreyknvl@google.com
Fixes: aa1ef4d7b3f6 ("kasan, mm: reset tags when accessing metadata")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    2 ++
 1 file changed, 2 insertions(+)
diff mbox series

Patch

--- a/mm/page_alloc.c~kasan-mm-fix-resetting-page_alloc-tags-for-hw_tags
+++ a/mm/page_alloc.c
@@ -1207,8 +1207,10 @@  static void kernel_init_free_pages(struc
 	/* 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);
 	}
 	kasan_enable_current();
 }