The patch titled
Subject: x86: kmsan: handle CPU entry area
has been added to the -mm mm-unstable branch. Its filename is
x86-kmsan-handle-cpu-entry-area.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/x86-kmsan-handle-cpu-entry-area.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: x86: kmsan: handle CPU entry area
Date: Wed, 28 Sep 2022 14:32:19 +0200
Among other data, CPU entry area holds exception stacks, so addresses from
this area can be passed to kmsan_get_metadata().
This previously led to kmsan_get_metadata() returning NULL, which in turn
resulted in a warning that triggered further attempts to call
kmsan_get_metadata() in the exception context, which quickly exhausted the
exception stack.
This patch allocates shadow and origin for the CPU entry area on x86 and
introduces arch_kmsan_get_meta_or_null(), which performs arch-specific
metadata mapping.
Link: https://lkml.kernel.org/r/20220928123219.1101883-1-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Fixes: 21d723a7c1409 ("kmsan: add KMSAN runtime core")
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/arch/x86/include/asm/kmsan.h~x86-kmsan-handle-cpu-entry-area
+++ a/arch/x86/include/asm/kmsan.h
@@ -11,9 +11,41 @@
#ifndef MODULE
+#include <asm/cpu_entry_area.h>
#include <asm/processor.h>
#include <linux/mmzone.h>
+DECLARE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_shadow);
+DECLARE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_origin);
+
+/*
+ * Functions below are declared in the header to make sure they are inlined.
+ * They all are called from kmsan_get_metadata() for every memory access in
+ * the kernel, so speed is important here.
+ */
+
+/*
+ * Compute metadata addresses for the CPU entry area on x86.
+ */
+static inline void *arch_kmsan_get_meta_or_null(void *addr, bool is_origin)
+{
+ unsigned long addr64 = (unsigned long)addr;
+ char *metadata_array;
+ unsigned long off;
+ int cpu;
+
+ if ((addr64 < CPU_ENTRY_AREA_BASE) ||
+ (addr64 >= (CPU_ENTRY_AREA_BASE + CPU_ENTRY_AREA_MAP_SIZE)))
+ return NULL;
+ cpu = (addr64 - CPU_ENTRY_AREA_BASE) / CPU_ENTRY_AREA_SIZE;
+ off = addr64 - (unsigned long)get_cpu_entry_area(cpu);
+ if ((off < 0) || (off >= CPU_ENTRY_AREA_SIZE))
+ return NULL;
+ metadata_array = is_origin ? cpu_entry_area_origin :
+ cpu_entry_area_shadow;
+ return &per_cpu(metadata_array[off], cpu);
+}
+
/*
* Taken from arch/x86/mm/physaddr.h to avoid using an instrumented version.
*/
--- /dev/null
+++ a/arch/x86/mm/kmsan_shadow.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * x86-specific bits of KMSAN shadow implementation.
+ *
+ * Copyright (C) 2022 Google LLC
+ * Author: Alexander Potapenko <glider@xxxxxxxxxx>
+ */
+
+#include <asm/cpu_entry_area.h>
+#include <linux/percpu-defs.h>
+
+/*
+ * Addresses within the CPU entry area (including e.g. exception stacks) do not
+ * have struct page entries corresponding to them, so they need separate
+ * handling.
+ * arch_kmsan_get_meta_or_null() (declared in the header) maps the addresses in
+ * CPU entry area to addresses in cpu_entry_area_shadow/cpu_entry_area_origin.
+ */
+DEFINE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_shadow);
+DEFINE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_origin);
--- a/arch/x86/mm/Makefile~x86-kmsan-handle-cpu-entry-area
+++ a/arch/x86/mm/Makefile
@@ -46,6 +46,9 @@ obj-$(CONFIG_HIGHMEM) += highmem_32.o
KASAN_SANITIZE_kasan_init_$(BITS).o := n
obj-$(CONFIG_KASAN) += kasan_init_$(BITS).o
+KMSAN_SANITIZE_kmsan_shadow.o := n
+obj-$(CONFIG_KMSAN) += kmsan_shadow.o
+
obj-$(CONFIG_MMIOTRACE) += mmiotrace.o
mmiotrace-y := kmmio.o pf_in.o mmio-mod.o
obj-$(CONFIG_MMIOTRACE_TEST) += testmmiotrace.o
--- a/MAINTAINERS~x86-kmsan-handle-cpu-entry-area
+++ a/MAINTAINERS
@@ -11379,6 +11379,7 @@ L: kasan-dev@xxxxxxxxxxxxxxxx
S: Maintained
F: Documentation/dev-tools/kmsan.rst
F: arch/*/include/asm/kmsan.h
+F: arch/*/mm/kmsan_*
F: include/linux/kmsan*.h
F: lib/Kconfig.kmsan
F: mm/kmsan/
--- a/mm/kmsan/shadow.c~x86-kmsan-handle-cpu-entry-area
+++ a/mm/kmsan/shadow.c
@@ -12,7 +12,6 @@
#include <linux/cacheflush.h>
#include <linux/memblock.h>
#include <linux/mm_types.h>
-#include <linux/percpu-defs.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/stddef.h>
@@ -126,6 +125,7 @@ void *kmsan_get_metadata(void *address,
{
u64 addr = (u64)address, pad, off;
struct page *page;
+ void *ret;
if (is_origin && !IS_ALIGNED(addr, KMSAN_ORIGIN_SIZE)) {
pad = addr % KMSAN_ORIGIN_SIZE;
@@ -136,6 +136,10 @@ void *kmsan_get_metadata(void *address,
kmsan_internal_is_module_addr(address))
return (void *)vmalloc_meta(address, is_origin);
+ ret = arch_kmsan_get_meta_or_null(address, is_origin);
+ if (ret)
+ return ret;
+
page = virt_to_page_or_null(address);
if (!page)
return NULL;
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
stackdepot-reserve-5-extra-bits-in-depot_stack_handle_t.patch
instrumentedh-allow-instrumenting-both-sides-of-copy_from_user.patch
x86-asm-instrument-usercopy-in-get_user-and-put_user.patch
asm-generic-instrument-usercopy-in-cacheflushh.patch
kmsan-add-rest-documentation.patch
kmsan-introduce-__no_sanitize_memory-and-__no_kmsan_checks.patch
kmsan-mark-noinstr-as-__no_sanitize_memory.patch
x86-kmsan-pgtable-reduce-vmalloc-space.patch
libnvdimm-pfn_dev-increase-max_struct_page_size.patch
kmsan-add-kmsan-runtime-core.patch
kmsan-disable-instrumentation-of-unsupported-common-kernel-code.patch
maintainers-add-entry-for-kmsan.patch
mm-kmsan-maintain-kmsan-metadata-for-page-operations.patch
mm-kmsan-call-kmsan-hooks-from-slub-code.patch
kmsan-handle-task-creation-and-exiting.patch
init-kmsan-call-kmsan-initialization-routines.patch
instrumentedh-add-kmsan-support.patch
kmsan-add-iomap-support.patch
input-libps2-mark-data-received-in-__ps2_command-as-initialized.patch
dma-kmsan-unpoison-dma-mappings.patch
virtio-kmsan-check-unpoison-scatterlist-in-vring_map_one_sg.patch
kmsan-handle-memory-sent-to-from-usb.patch
kmsan-add-tests-for-kmsan.patch
kmsan-disable-strscpy-optimization-under-kmsan.patch
crypto-kmsan-disable-accelerated-configs-under-kmsan.patch
kmsan-disable-physical-page-merging-in-biovec.patch
block-kmsan-skip-bio-block-merging-logic-for-kmsan.patch
kcov-kmsan-unpoison-area-list-in-kcov_remote_area_put.patch
security-kmsan-fix-interoperability-with-auto-initialization.patch
objtool-kmsan-list-kmsan-api-functions-as-uaccess-safe.patch
x86-kmsan-disable-instrumentation-of-unsupported-code.patch
x86-kmsan-skip-shadow-checks-in-__switch_to.patch
x86-kmsan-handle-open-coded-assembly-in-lib-iomemc.patch
x86-kmsan-use-__msan_-string-functions-where-possible.patch
x86-kmsan-sync-metadata-pages-on-page-fault.patch
x86-kasan-kmsan-support-config_generic_csum-on-x86-enable-it-for-kasan-kmsan.patch
x86-fs-kmsan-disable-config_dcache_word_access.patch
x86-kmsan-dont-instrument-stack-walking-functions.patch
entry-kmsan-introduce-kmsan_unpoison_entry_regs.patch
bpf-kmsan-initialize-bpf-registers-with-zeroes.patch
mm-fs-initialize-fsdata-passed-to-write_begin-write_end-interface.patch
x86-kmsan-enable-kmsan-builds-for-x86.patch
x86-kmsan-handle-cpu-entry-area.patch
