Commit eb6efdfe authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Andrew Morton
Browse files

s390/uaccess: add KMSAN support to put_user() and get_user() 

put_user() uses inline assembly with precise constraints, so Clang is in
principle capable of instrumenting it automatically.  Unfortunately, one
of the constraints contains a dereferenced user pointer, and Clang does
not currently distinguish user and kernel pointers.  Therefore KMSAN
attempts to access shadow for user pointers, which is not a right thing to
do.

An obvious fix to add __no_sanitize_memory to __put_user_fn() does not
work, since it's __always_inline.  And __always_inline cannot be removed
due to the __put_user_bad() trick.

A different obvious fix of using the "a" instead of the "+Q" constraint
degrades the code quality, which is very important here, since it's a hot
path.

Instead, repurpose the __put_user_asm() macro to define
__put_user_{char,short,int,long}_noinstr() functions and mark them with
__no_sanitize_memory.  For the non-KMSAN builds make them __always_inline
in order to keep the generated code quality.  Also define
__put_user_{char,short,int,long}() functions, which call the
aforementioned ones and which *are* instrumented, because they call KMSAN
hooks, which may be implemented as macros.

The same applies to get_user() as well.

Link: https://lkml.kernel.org/r/20240621113706.315500-35-iii@linux.ibm.com


Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Acked-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Reviewed-by: default avatarAlexander Potapenko <glider@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <kasan-dev@googlegroups.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c1057a70

arch/s390/include/asm/uaccess.h

+79 −32
Original line number Diff line number Diff line
@@ -78,13 +78,24 @@ union oac { 


int __noreturn __put_user_bad(void);



#define __put_user_asm(to, from, size)					\

({									\

#ifdef CONFIG_KMSAN

#define get_put_user_noinstr_attributes \

	noinline __maybe_unused __no_sanitize_memory

#else

#define get_put_user_noinstr_attributes __always_inline

#endif



#define DEFINE_PUT_USER(type)						\

static get_put_user_noinstr_attributes int				\

__put_user_##type##_noinstr(unsigned type __user *to,			\

			    unsigned type *from,			\

			    unsigned long size)				\

{									\

	union oac __oac_spec = {					\

		.oac1.as = PSW_BITS_AS_SECONDARY,			\

		.oac1.a = 1,						\

	};								\

	int __rc;							\

	int rc;								\

									\

	asm volatile(							\

		"	lr	0,%[spec]\n"				\
@@ -93,12 +104,28 @@ int __noreturn __put_user_bad(void); 
		"2:\n"							\

		EX_TABLE_UA_STORE(0b, 2b, %[rc])			\

		EX_TABLE_UA_STORE(1b, 2b, %[rc])			\

		: [rc] "=&d" (__rc), [_to] "+Q" (*(to))			\

		: [rc] "=&d" (rc), [_to] "+Q" (*(to))			\

		: [_size] "d" (size), [_from] "Q" (*(from)),		\

		  [spec] "d" (__oac_spec.val)				\

		: "cc", "0");						\

	__rc;								\

})

	return rc;							\

}									\

									\

static __always_inline int						\

__put_user_##type(unsigned type __user *to, unsigned type *from,	\

		  unsigned long size)					\

{									\

	int rc;								\

									\

	rc = __put_user_##type##_noinstr(to, from, size);		\

	instrument_put_user(*from, to, size);				\

	return rc;							\

}



DEFINE_PUT_USER(char);

DEFINE_PUT_USER(short);

DEFINE_PUT_USER(int);

DEFINE_PUT_USER(long);



static __always_inline int __put_user_fn(void *x, void __user *ptr, unsigned long size)

{
@@ -106,22 +133,22 @@ static __always_inline int __put_user_fn(void *x, void __user *ptr, unsigned lon 


	switch (size) {

	case 1:

		rc = __put_user_asm((unsigned char __user *)ptr,

		rc = __put_user_char((unsigned char __user *)ptr,

				     (unsigned char *)x,

				     size);

		break;

	case 2:

		rc = __put_user_asm((unsigned short __user *)ptr,

		rc = __put_user_short((unsigned short __user *)ptr,

				      (unsigned short *)x,

				      size);

		break;

	case 4:

		rc = __put_user_asm((unsigned int __user *)ptr,

		rc = __put_user_int((unsigned int __user *)ptr,

				    (unsigned int *)x,

				    size);

		break;

	case 8:

		rc = __put_user_asm((unsigned long __user *)ptr,

		rc = __put_user_long((unsigned long __user *)ptr,

				     (unsigned long *)x,

				     size);

		break;
@@ -134,13 +161,17 @@ static __always_inline int __put_user_fn(void *x, void __user *ptr, unsigned lon 


int __noreturn __get_user_bad(void);



#define __get_user_asm(to, from, size)					\

({									\

#define DEFINE_GET_USER(type)						\

static get_put_user_noinstr_attributes int				\

__get_user_##type##_noinstr(unsigned type *to,				\

			    unsigned type __user *from,			\

			    unsigned long size)				\

{									\

	union oac __oac_spec = {					\

		.oac2.as = PSW_BITS_AS_SECONDARY,			\

		.oac2.a = 1,						\

	};								\

	int __rc;							\

	int rc;								\

									\

	asm volatile(							\

		"	lr	0,%[spec]\n"				\
@@ -149,13 +180,29 @@ int __noreturn __get_user_bad(void); 
		"2:\n"							\

		EX_TABLE_UA_LOAD_MEM(0b, 2b, %[rc], %[_to], %[_ksize])	\

		EX_TABLE_UA_LOAD_MEM(1b, 2b, %[rc], %[_to], %[_ksize])	\

		: [rc] "=&d" (__rc), "=Q" (*(to))			\

		: [rc] "=&d" (rc), "=Q" (*(to))				\

		: [_size] "d" (size), [_from] "Q" (*(from)),		\

		  [spec] "d" (__oac_spec.val), [_to] "a" (to),		\

		  [_ksize] "K" (size)					\

		: "cc", "0");						\

	__rc;								\

})

	return rc;							\

}									\

									\

static __always_inline int						\

__get_user_##type(unsigned type *to, unsigned type __user *from,	\

		  unsigned long size)					\

{									\

	int rc;								\

									\

	rc = __get_user_##type##_noinstr(to, from, size);		\

	instrument_get_user(*to);					\

	return rc;							\

}



DEFINE_GET_USER(char);

DEFINE_GET_USER(short);

DEFINE_GET_USER(int);

DEFINE_GET_USER(long);



static __always_inline int __get_user_fn(void *x, const void __user *ptr, unsigned long size)

{
@@ -163,22 +210,22 @@ static __always_inline int __get_user_fn(void *x, const void __user *ptr, unsign 


	switch (size) {

	case 1:

		rc = __get_user_asm((unsigned char *)x,

		rc = __get_user_char((unsigned char *)x,

				     (unsigned char __user *)ptr,

				     size);

		break;

	case 2:

		rc = __get_user_asm((unsigned short *)x,

		rc = __get_user_short((unsigned short *)x,

				      (unsigned short __user *)ptr,

				      size);

		break;

	case 4:

		rc = __get_user_asm((unsigned int *)x,

		rc = __get_user_int((unsigned int *)x,

				    (unsigned int __user *)ptr,

				    size);

		break;

	case 8:

		rc = __get_user_asm((unsigned long *)x,

		rc = __get_user_long((unsigned long *)x,

				     (unsigned long __user *)ptr,

				     size);

		break;