[merged mm-stable] s390-uaccess-add-kmsan-support-to-put_user-and-get_user.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
Subject: s390/uaccess: add KMSAN support to put_user() and get_user()
has been removed from the -mm tree. Its filename was
s390-uaccess-add-kmsan-support-to-put_user-and-get_user.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Ilya Leoshkevich <i...@linux.ibm.com>
Subject: s390/uaccess: add KMSAN support to put_user() and get_user()
Date: Fri, 21 Jun 2024 13:35:18 +0200

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...@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
Acked-by: Heiko Carstens <h...@linux.ibm.com>
Reviewed-by: Alexander Potapenko <gli...@google.com>
Cc: Alexander Gordeev <agor...@linux.ibm.com>
Cc: Christian Borntraeger <bornt...@linux.ibm.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: David Rientjes <rien...@google.com>
Cc: Dmitry Vyukov <dvy...@google.com>
Cc: Hyeonggon Yoo <42.h...@gmail.com>
Cc: Joonsoo Kim <iamjoon...@lge.com>
Cc: <kasa...@googlegroups.com>
Cc: Marco Elver <el...@google.com>
Cc: Mark Rutland <mark.r...@arm.com>
Cc: Masami Hiramatsu (Google) <mhir...@kernel.org>
Cc: Pekka Enberg <pen...@kernel.org>
Cc: Roman Gushchin <roman.g...@linux.dev>
Cc: Steven Rostedt (Google) <ros...@goodmis.org>
Cc: Sven Schnelle <sv...@linux.ibm.com>
Cc: Vasily Gorbik <g...@linux.ibm.com>
Cc: Vlastimil Babka <vba...@suse.cz>
Signed-off-by: Andrew Morton <ak...@linux-foundation.org>
---

arch/s390/include/asm/uaccess.h | 111 +++++++++++++++++++++---------
1 file changed, 79 insertions(+), 32 deletions(-)

--- a/arch/s390/include/asm/uaccess.h~s390-uaccess-add-kmsan-support-to-put_user-and-get_user
+++ a/arch/s390/include/asm/uaccess.h
@@ -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)
{
@@ -106,24 +133,24 @@ static __always_inline int __put_user_fn

switch (size) {
case 1:
- rc = __put_user_asm((unsigned char __user *)ptr,
- (unsigned char *)x,
- size);
+ rc = __put_user_char((unsigned char __user *)ptr,
+ (unsigned char *)x,
+ size);
break;
case 2:
- rc = __put_user_asm((unsigned short __user *)ptr,
- (unsigned short *)x,
- size);
+ 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,
- (unsigned long *)x,
- size);
+ rc = __put_user_long((unsigned long __user *)ptr,
+ (unsigned long *)x,
+ size);
break;
default:
__put_user_bad();
@@ -134,13 +161,17 @@ static __always_inline int __put_user_fn

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)
{
@@ -163,24 +210,24 @@ static __always_inline int __get_user_fn

switch (size) {
case 1:
- rc = __get_user_asm((unsigned char *)x,
- (unsigned char __user *)ptr,
- size);
+ rc = __get_user_char((unsigned char *)x,
+ (unsigned char __user *)ptr,
+ size);
break;
case 2:
- rc = __get_user_asm((unsigned short *)x,
- (unsigned short __user *)ptr,
- size);
+ 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,
- (unsigned long __user *)ptr,
- size);
+ rc = __get_user_long((unsigned long *)x,
+ (unsigned long __user *)ptr,
+ size);
break;
default:
__get_user_bad();
_

Patches currently in -mm which might be from i...@linux.ibm.com are