arm64, kfence: enable KFENCE for ARM64

Add architecture specific implementation details for KFENCE and enable
KFENCE for the arm64 architecture. In particular, this implements the
required interface in <asm/kfence.h>.

KFENCE requires that attributes for pages from its memory pool can
individually be set. Therefore, force the entire linear map to be mapped
at page granularity. Doing so may result in extra memory allocated for
page tables in case rodata=full is not set; however, currently
CONFIG_RODATA_FULL_DEFAULT_ENABLED=y is the default, and the common case
is therefore not affected by this change.

[elver@google.com: add missing copyright and description header]
Link: https://lkml.kernel.org/r/20210118092159.145934-3-elver@google.com
Link: https://lkml.kernel.org/r/20201103175841.3495947-4-elver@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Co-developed-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Jann Horn <jannh@google.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.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: 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>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fc0ce2a1f3bfa63a10091a012fd2ec946d81a012..a254f4871683f0c62156662a1e4b01137bf2c1b6 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -140,6 +140,7 @@ config ARM64
        select HAVE_ARCH_KASAN if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
        select HAVE_ARCH_KASAN_SW_TAGS if HAVE_ARCH_KASAN
        select HAVE_ARCH_KASAN_HW_TAGS if (HAVE_ARCH_KASAN && ARM64_MTE)
+       select HAVE_ARCH_KFENCE
        select HAVE_ARCH_KGDB
        select HAVE_ARCH_MMAP_RND_BITS
        select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT

diff --git a/arch/arm64/include/asm/kfence.h b/arch/arm64/include/asm/kfence.h
new file mode 100644 (file)
index 0000000..42a06f8
--- /dev/null
+++ b/arch/arm64/include/asm/kfence.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * arm64 KFENCE support.
+ *
+ * Copyright (C) 2020, Google LLC.
+ */
+
+#ifndef __ASM_KFENCE_H
+#define __ASM_KFENCE_H
+
+#include <asm/cacheflush.h>
+
+#define KFENCE_SKIP_ARCH_FAULT_HANDLER "el1_sync"
+
+static inline bool arch_kfence_init_pool(void) { return true; }
+
+static inline bool kfence_protect_page(unsigned long addr, bool protect)
+{
+       set_memory_valid(addr, 1, !protect);
+
+       return true;
+}
+
+#endif /* __ASM_KFENCE_H */

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index dc9f96442edcedb9dbe37e92619f4479fa21f15a..42515900ab2e6d08ad65398adc61246ad7763408 100644 (file)
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -10,6 +10,7 @@
 #include <linux/acpi.h>
 #include <linux/bitfield.h>
 #include <linux/extable.h>
+#include <linux/kfence.h>
 #include <linux/signal.h>
 #include <linux/mm.h>
 #include <linux/hardirq.h>
@@ -389,6 +390,9 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr,
        } else if (addr < PAGE_SIZE) {
                msg = "NULL pointer dereference";
        } else {
+               if (kfence_handle_page_fault(addr))
+                       return;
+
                msg = "paging request";
        }
 

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index d0758d24a42de79fadc0c2ad60097b1985ce87a3..ef7698c4e2f083660b83c47b6c6327d1c68f6e24 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1465,7 +1465,13 @@ int arch_add_memory(int nid, u64 start, u64 size,
        int ret, flags = 0;
 
        VM_BUG_ON(!mhp_range_allowed(start, size, true));
-       if (rodata_full || debug_pagealloc_enabled())
+
+       /*
+        * KFENCE requires linear map to be mapped at page granularity, so that
+        * it is possible to protect/unprotect single pages in the KFENCE pool.
+        */
+       if (rodata_full || debug_pagealloc_enabled() ||
+           IS_ENABLED(CONFIG_KFENCE))
                flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
        __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),