linux-kernel - [PATCH 3.18 14/50] asm-generic: Fix local variable shadow in __set_fixmap

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Date:   Mon,  1 Apr 2019 19:02:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 3.18 14/50] asm-generic: Fix local variable shadow in __set_fixmap_offset

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 3694bd76781b76c4f8d2ecd85018feeb1609f0e5 ]

Currently __set_fixmap_offset is a macro function which has a local
variable called 'addr'. If a caller passes a 'phys' parameter which is
derived from a variable also called 'addr', the local variable will
shadow this, and the compiler will complain about the use of an
uninitialized variable. To avoid the issue with namespace clashes,
'addr' is prefixed with a liberal sprinkling of underscores.

Turning __set_fixmap_offset into a static inline breaks the build for
several architectures. Fixing this properly requires updates to a number
of architectures to make them agree on the prototype of __set_fixmap (it
could be done as a subsequent patch series).

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Arnd Bergmann <arnd@...db.de>
[catalin.marinas@....com: squashed the original function patch and macro fixup]
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/asm-generic/fixmap.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
index f23174fb9ec4..10889b63af8f 100644
--- a/include/asm-generic/fixmap.h
+++ b/include/asm-generic/fixmap.h
@@ -67,12 +67,12 @@ static inline unsigned long virt_to_fix(const unsigned long vaddr)
 #endif
 
 /* Return a pointer with offset calculated */
-#define __set_fixmap_offset(idx, phys, flags)		      \
-({							      \
-	unsigned long addr;				      \
-	__set_fixmap(idx, phys, flags);			      \
-	addr = fix_to_virt(idx) + ((phys) & (PAGE_SIZE - 1)); \
-	addr;						      \
+#define __set_fixmap_offset(idx, phys, flags)				\
+({									\
+	unsigned long ________addr;					\
+	__set_fixmap(idx, phys, flags);					\
+	________addr = fix_to_virt(idx) + ((phys) & (PAGE_SIZE - 1));	\
+	________addr;							\
 })
 
 #define set_fixmap_offset(idx, phys) \
-- 
2.19.1