Commit 69d4c0d3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

entry, kasan, x86: Disallow overriding mem*() functions 



KASAN cannot just hijack the mem*() functions, it needs to emit
__asan_mem*() variants if it wants instrumentation (other sanitizers
already do this).

  vmlinux.o: warning: objtool: sync_regs+0x24: call to memcpy() leaves .noinstr.text section
  vmlinux.o: warning: objtool: vc_switch_off_ist+0xbe: call to memcpy() leaves .noinstr.text section
  vmlinux.o: warning: objtool: fixup_bad_iret+0x36: call to memset() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __sev_get_ghcb+0xa0: call to memcpy() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __sev_put_ghcb+0x35: call to memcpy() leaves .noinstr.text section

Remove the weak aliases to ensure nobody hijacks these functions and
add them to the noinstr section.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Tested-by: default avatarTony Lindgren <tony@atomide.com>
Tested-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195542.028523143@infradead.org
parent 365bd03f

arch/x86/lib/memcpy_64.S

+2 −3
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ 
#include <asm/alternative.h>

#include <asm/export.h>



.pushsection .noinstr.text, "ax"

.section .noinstr.text, "ax"



/*

 * We build a jump to memcpy_orig by default which gets NOPped out on
@@ -43,7 +43,7 @@ SYM_TYPED_FUNC_START(__memcpy) 
SYM_FUNC_END(__memcpy)

EXPORT_SYMBOL(__memcpy)



SYM_FUNC_ALIAS_WEAK(memcpy, __memcpy)

SYM_FUNC_ALIAS(memcpy, __memcpy)

EXPORT_SYMBOL(memcpy)



/*
@@ -184,4 +184,3 @@ SYM_FUNC_START_LOCAL(memcpy_orig) 
	RET

SYM_FUNC_END(memcpy_orig)

.popsection

arch/x86/lib/memmove_64.S

+3 −1
Original line number Diff line number Diff line
@@ -13,6 +13,8 @@ 


#undef memmove



.section .noinstr.text, "ax"



/*

 * Implement memmove(). This can handle overlap between src and dst.

 *
@@ -213,5 +215,5 @@ SYM_FUNC_START(__memmove) 
SYM_FUNC_END(__memmove)

EXPORT_SYMBOL(__memmove)



SYM_FUNC_ALIAS_WEAK(memmove, __memmove)

SYM_FUNC_ALIAS(memmove, __memmove)

EXPORT_SYMBOL(memmove)

arch/x86/lib/memset_64.S

+3 −1
Original line number Diff line number Diff line
@@ -6,6 +6,8 @@ 
#include <asm/alternative.h>

#include <asm/export.h>



.section .noinstr.text, "ax"



/*

 * ISO C memset - set a memory block to a byte value. This function uses fast

 * string to get better performance than the original function. The code is
@@ -43,7 +45,7 @@ SYM_FUNC_START(__memset) 
SYM_FUNC_END(__memset)

EXPORT_SYMBOL(__memset)



SYM_FUNC_ALIAS_WEAK(memset, __memset)

SYM_FUNC_ALIAS(memset, __memset)

EXPORT_SYMBOL(memset)



/*

mm/kasan/kasan.h

+4 −0
Original line number Diff line number Diff line
@@ -618,6 +618,10 @@ void __asan_set_shadow_f3(const void *addr, size_t size); 
void __asan_set_shadow_f5(const void *addr, size_t size);

void __asan_set_shadow_f8(const void *addr, size_t size);



void *__asan_memset(void *addr, int c, size_t len);

void *__asan_memmove(void *dest, const void *src, size_t len);

void *__asan_memcpy(void *dest, const void *src, size_t len);



void __hwasan_load1_noabort(unsigned long addr);

void __hwasan_store1_noabort(unsigned long addr);

void __hwasan_load2_noabort(unsigned long addr);

mm/kasan/shadow.c

+38 −0
Original line number Diff line number Diff line
@@ -38,6 +38,12 @@ bool __kasan_check_write(const volatile void *p, unsigned int size) 
}

EXPORT_SYMBOL(__kasan_check_write);



#ifndef CONFIG_GENERIC_ENTRY

/*

 * CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be

 * instrumented. KASAN enabled toolchains should emit __asan_mem*() functions

 * for the sites they want to instrument.

 */

#undef memset

void *memset(void *addr, int c, size_t len)

{
@@ -68,6 +74,38 @@ void *memcpy(void *dest, const void *src, size_t len) 


	return __memcpy(dest, src, len);

}

#endif



void *__asan_memset(void *addr, int c, size_t len)

{

	if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_))

		return NULL;



	return __memset(addr, c, len);

}

EXPORT_SYMBOL(__asan_memset);



#ifdef __HAVE_ARCH_MEMMOVE

void *__asan_memmove(void *dest, const void *src, size_t len)

{

	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||

	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))

		return NULL;



	return __memmove(dest, src, len);

}

EXPORT_SYMBOL(__asan_memmove);

#endif



void *__asan_memcpy(void *dest, const void *src, size_t len)

{

	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||

	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))

		return NULL;



	return __memcpy(dest, src, len);

}

EXPORT_SYMBOL(__asan_memcpy);



void kasan_poison(const void *addr, size_t size, u8 value, bool init)

{