From 2b8305260fb37fc20e13f71e13073304d0a031c8 Mon Sep 17 00:00:00 2001
From: Alexander Potapenko <glider@google.com>
Date: Thu, 25 Feb 2021 17:19:21 -0800
Subject: kfence, kasan: make KFENCE compatible with KASAN

Make KFENCE compatible with KASAN. Currently this helps test KFENCE
itself, where KASAN can catch potential corruptions to KFENCE state, or
other corruptions that may be a result of freepointer corruptions in the
main allocators.

[akpm@linux-foundation.org: merge fixup]
[andreyknvl@google.com: untag addresses for KFENCE]
  Link: https://lkml.kernel.org/r/9dc196006921b191d25d10f6e611316db7da2efc.1611946152.git.andreyknvl@google.com

Link: https://lkml.kernel.org/r/20201103175841.3495947-7-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Jann Horn <jannh@google.com>
Co-developed-by: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joern Engel <joern@purestorage.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: SeongJae Park <sjpark@amazon.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/kasan/shadow.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'mm/kasan/shadow.c')

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 80adc85d0393..1372a2fc0ca9 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
+#include <linux/kfence.h>
 #include <linux/kmemleak.h>
 #include <linux/memory.h>
 #include <linux/mm.h>
@@ -84,6 +85,10 @@ void kasan_poison(const void *address, size_t size, u8 value)
 	address = kasan_reset_tag(address);
 	size = round_up(size, KASAN_GRANULE_SIZE);
 
+	/* Skip KFENCE memory if called explicitly outside of sl*b. */
+	if (is_kfence_address(address))
+		return;
+
 	shadow_start = kasan_mem_to_shadow(address);
 	shadow_end = kasan_mem_to_shadow(address + size);
 
@@ -102,6 +107,14 @@ void kasan_unpoison(const void *address, size_t size)
 	 */
 	address = kasan_reset_tag(address);
 
+	/*
+	 * Skip KFENCE memory if called explicitly outside of sl*b. Also note
+	 * that calls to ksize(), where size is not a multiple of machine-word
+	 * size, would otherwise poison the invalid portion of the word.
+	 */
+	if (is_kfence_address(address))
+		return;
+
 	kasan_poison(address, size, tag);
 
 	if (size & KASAN_GRANULE_MASK) {
-- 
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