Commit d6d51a96 authored by Linus Walleij's avatar Linus Walleij Committed by Russell King
Browse files

ARM: 9014/2: Replace string mem* functions for KASan 



Functions like memset()/memmove()/memcpy() do a lot of memory
accesses.

If a bad pointer is passed to one of these functions it is important
to catch this. Compiler instrumentation cannot do this since these
functions are written in assembly.

KASan replaces these memory functions with instrumented variants.

The original functions are declared as weak symbols so that
the strong definitions in mm/kasan/kasan.c can replace them.

The original functions have aliases with a '__' prefix in their
name, so we can call the non-instrumented variant if needed.

We must use __memcpy()/__memset() in place of memcpy()/memset()
when we copy .data to RAM and when we clear .bss, because
kasan_early_init cannot be called before the initialization of
.data and .bss.

For the kernel compression and EFI libstub's custom string
libraries we need a special quirk: even if these are built
without KASan enabled, they rely on the global headers for their
custom string libraries, which means that e.g. memcpy()
will be defined to __memcpy() and we get link failures.
Since these implementations are written i C rather than
assembly we use e.g. __alias(memcpy) to redirected any
users back to the local implementation.

Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: kasan-dev@googlegroups.com
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Tested-by: Ard Biesheuvel <ardb@kernel.org> # QEMU/KVM/mach-virt/LPAE/8G
Tested-by: Florian Fainelli <f.fainelli@gmail.com> # Brahma SoCs
Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de> # i.MX6Q
Reported-by: default avatarRussell King - ARM Linux <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarAhmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: default avatarAbbott Liu <liuwenliang@huawei.com>
Signed-off-by: default avatarFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
parent d5d44e7e

arch/arm/boot/compressed/string.c

+19 −0
Original line number Diff line number Diff line
@@ -7,6 +7,25 @@ 


#include <linux/string.h>



/*

 * The decompressor is built without KASan but uses the same redirects as the

 * rest of the kernel when CONFIG_KASAN is enabled, defining e.g. memcpy()

 * to __memcpy() but since we are not linking with the main kernel string

 * library in the decompressor, that will lead to link failures.

 *

 * Undefine KASan's versions, define the wrapped functions and alias them to

 * the right names so that when e.g. __memcpy() appear in the code, it will

 * still be linked to this local version of memcpy().

 */

#ifdef CONFIG_KASAN

#undef memcpy

#undef memmove

#undef memset

void *__memcpy(void *__dest, __const void *__src, size_t __n) __alias(memcpy);

void *__memmove(void *__dest, __const void *__src, size_t count) __alias(memmove);

void *__memset(void *s, int c, size_t count) __alias(memset);

#endif



void *memcpy(void *__dest, __const void *__src, size_t __n)

{

	int i = 0;

arch/arm/include/asm/string.h

+26 −0
Original line number Diff line number Diff line
@@ -5,6 +5,9 @@ 
/*

 * We don't do inline string functions, since the

 * optimised inline asm versions are not small.

 *

 * The __underscore versions of some functions are for KASan to be able

 * to replace them with instrumented versions.

 */



#define __HAVE_ARCH_STRRCHR
@@ -15,15 +18,18 @@ extern char * strchr(const char * s, int c); 


#define __HAVE_ARCH_MEMCPY

extern void * memcpy(void *, const void *, __kernel_size_t);

extern void *__memcpy(void *dest, const void *src, __kernel_size_t n);



#define __HAVE_ARCH_MEMMOVE

extern void * memmove(void *, const void *, __kernel_size_t);

extern void *__memmove(void *dest, const void *src, __kernel_size_t n);



#define __HAVE_ARCH_MEMCHR

extern void * memchr(const void *, int, __kernel_size_t);



#define __HAVE_ARCH_MEMSET

extern void * memset(void *, int, __kernel_size_t);

extern void *__memset(void *s, int c, __kernel_size_t n);



#define __HAVE_ARCH_MEMSET32

extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t);
@@ -39,4 +45,24 @@ static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n) 
	return __memset64(p, v, n * 8, v >> 32);

}



/*

 * For files that are not instrumented (e.g. mm/slub.c) we

 * must use non-instrumented versions of the mem*

 * functions named __memcpy() etc. All such kernel code has

 * been tagged with KASAN_SANITIZE_file.o = n, which means

 * that the address sanitization argument isn't passed to the

 * compiler, and __SANITIZE_ADDRESS__ is not set. As a result

 * these defines kick in.

 */

#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)

#define memcpy(dst, src, len) __memcpy(dst, src, len)

#define memmove(dst, src, len) __memmove(dst, src, len)

#define memset(s, c, n) __memset(s, c, n)



#ifndef __NO_FORTIFY

#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */

#endif



#endif



#endif

arch/arm/kernel/head-common.S

+2 −2
Original line number Diff line number Diff line
@@ -95,7 +95,7 @@ __mmap_switched: 
 THUMB(	ldmia	r4!, {r0, r1, r2, r3} )

 THUMB(	mov	sp, r3 )

	sub	r2, r2, r1

	bl	memcpy				@ copy .data to RAM

	bl	__memcpy			@ copy .data to RAM

#endif



   ARM(	ldmia	r4!, {r0, r1, sp} )
@@ -103,7 +103,7 @@ __mmap_switched: 
 THUMB(	mov	sp, r3 )

	sub	r2, r1, r0

	mov	r1, #0

	bl	memset				@ clear .bss

	bl	__memset			@ clear .bss



	ldmia	r4, {r0, r1, r2, r3}

	str	r9, [r0]			@ Save processor ID

arch/arm/lib/memcpy.S

+3 −0
Original line number Diff line number Diff line
@@ -58,6 +58,8 @@ 


/* Prototype: void *memcpy(void *dest, const void *src, size_t n); */



.weak memcpy

ENTRY(__memcpy)

ENTRY(mmiocpy)

ENTRY(memcpy)
@@ -65,3 +67,4 @@ ENTRY(memcpy) 


ENDPROC(memcpy)

ENDPROC(mmiocpy)

ENDPROC(__memcpy)

arch/arm/lib/memmove.S

+4 −1
Original line number Diff line number Diff line
@@ -24,12 +24,14 @@ 
 * occurring in the opposite direction.

 */



.weak memmove

ENTRY(__memmove)

ENTRY(memmove)

	UNWIND(	.fnstart			)



		subs	ip, r0, r1

		cmphi	r2, ip

		bls	memcpy

		bls	__memcpy



		stmfd	sp!, {r0, r4, lr}

	UNWIND(	.fnend				)
@@ -222,3 +224,4 @@ ENTRY(memmove) 
18:		backward_copy_shift	push=24	pull=8



ENDPROC(memmove)

ENDPROC(__memmove)

CRA Git | Maintained and supported by SUSTech CRA and CCSE