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From:   Max Filippov <jcmvbkbc@gmail.com>
To:     linux-xtensa@linux-xtensa.org, Al Viro <viro@zeniv.linux.org.uk>
Cc:     Chris Zankel <chris@zankel.net>, linux-kernel@vger.kernel.org,
        Max Filippov <jcmvbkbc@gmail.com>
Subject: [PATCH v2 3/4] xtensa: fix type conversion in __get_user_[no]check
Date:   Fri, 11 Oct 2019 17:37:07 -0700
Message-Id: <20191012003708.22182-4-jcmvbkbc@gmail.com>
In-Reply-To: <20191012003708.22182-1-jcmvbkbc@gmail.com>
References: <20191012003708.22182-1-jcmvbkbc@gmail.com>
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__get_user_[no]check uses temporary buffer of type long to store result
of __get_user_size and do sign extension on it when necessary. This
doesn't work correctly for 64-bit data. Fix it by moving temporary
buffer/sign extension logic to __get_user_asm.
Don't do assignment of __get_user_bad result to (x) as it may not always
be integer-compatible now and issue warning even when it's going to be
optimized. Instead do (x) = 0; and call __get_user_bad separately.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
Changes v1->v2:
- initialize result when access_ok check fails in __get_user_check

 arch/xtensa/include/asm/uaccess.h | 56 +++++++++++++++++--------------
 1 file changed, 30 insertions(+), 26 deletions(-)

diff --git a/arch/xtensa/include/asm/uaccess.h b/arch/xtensa/include/asm/uaccess.h
index aca510707189..43e923678dfb 100644
--- a/arch/xtensa/include/asm/uaccess.h
+++ b/arch/xtensa/include/asm/uaccess.h
@@ -172,19 +172,19 @@ __asm__ __volatile__(					\
 
 #define __get_user_nocheck(x, ptr, size)			\
 ({								\
-	long __gu_err, __gu_val;				\
-	__get_user_size(__gu_val, (ptr), (size), __gu_err);	\
-	(x) = (__force __typeof__(*(ptr)))__gu_val;		\
+	long __gu_err;						\
+	__get_user_size((x), (ptr), (size), __gu_err);		\
 	__gu_err;						\
 })
 
 #define __get_user_check(x, ptr, size)					\
 ({									\
-	long __gu_err = -EFAULT, __gu_val = 0;				\
+	long __gu_err = -EFAULT;					\
 	const __typeof__(*(ptr)) *__gu_addr = (ptr);			\
-	if (access_ok(__gu_addr, size))			\
-		__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
-	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
+	if (access_ok(__gu_addr, size))					\
+		__get_user_size((x), __gu_addr, (size), __gu_err);	\
+	else								\
+		(x) = 0;						\
 	__gu_err;							\
 })
 
@@ -208,7 +208,7 @@ do {									\
 		}							\
 		break;							\
 	}								\
-	default: (x) = __get_user_bad();				\
+	default: (x) = 0; __get_user_bad();				\
 	}								\
 } while (0)
 
@@ -218,24 +218,28 @@ do {									\
  * __check_align_* macros still work.
  */
 #define __get_user_asm(x_, addr_, err_, align, insn, cb) \
-__asm__ __volatile__(				\
-	__check_align_##align			\
-	"1: "insn"  %[x], %[addr], 0	\n"	\
-	"2:				\n"	\
-	"   .section  .fixup,\"ax\"	\n"	\
-	"   .align 4			\n"	\
-	"   .literal_position		\n"	\
-	"5:				\n"	\
-	"   movi   %[tmp], 2b		\n"	\
-	"   movi   %[x], 0		\n"	\
-	"   movi   %[err], %[efault]	\n"	\
-	"   jx     %[tmp]		\n"	\
-	"   .previous			\n"	\
-	"   .section  __ex_table,\"a\"	\n"	\
-	"   .long	1b, 5b		\n"	\
-	"   .previous"				\
-	:[err] "=r"(err_), [tmp] "=r"(cb), [x] "=r"(x_)\
-	:[addr] "r"(addr_), [efault] "i"(-EFAULT))
+do {							\
+	u32 __x;					\
+	__asm__ __volatile__(				\
+		__check_align_##align			\
+		"1: "insn"  %[x], %[addr], 0	\n"	\
+		"2:				\n"	\
+		"   .section  .fixup,\"ax\"	\n"	\
+		"   .align 4			\n"	\
+		"   .literal_position		\n"	\
+		"5:				\n"	\
+		"   movi   %[tmp], 2b		\n"	\
+		"   movi   %[x], 0		\n"	\
+		"   movi   %[err], %[efault]	\n"	\
+		"   jx     %[tmp]		\n"	\
+		"   .previous			\n"	\
+		"   .section  __ex_table,\"a\"	\n"	\
+		"   .long	1b, 5b		\n"	\
+		"   .previous"				\
+		:[err] "=r"(err_), [tmp] "=r"(cb), [x] "=r"(__x) \
+		:[addr] "r"(addr_), [efault] "i"(-EFAULT)); \
+	(x_) = (__force __typeof__(*(addr_)))__x;	\
+} while (0)
 
 
 /*
-- 
2.20.1