linux-kernel - [PATCH 4.19 25/54] bitops: protect variables in set_mask

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Message-Id: <20200411115511.029870714@linuxfoundation.org>
Date:   Sat, 11 Apr 2020 14:09:07 +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, Miklos Szeredi <mszeredi@...hat.com>,
        Theodore Tso <tytso@....edu>
Subject: [PATCH 4.19 25/54] bitops: protect variables in set_mask_bits() macro

From: Miklos Szeredi <mszeredi@...hat.com>

commit 18127429a854e7607b859484880b8e26cee9ddab upstream.

Unprotected naming of local variables within the set_mask_bits() can easily
lead to using the wrong scope.

Noticed this when "set_mask_bits(&foo->bar, 0, mask)" behaved as no-op.

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Fixes: 00a1a053ebe5 ("ext4: atomically set inode->i_flags in ext4_set_inode_flags()")
Cc: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/bitops.h |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -236,17 +236,17 @@ static __always_inline void __assign_bit
 #ifdef __KERNEL__
 
 #ifndef set_mask_bits
-#define set_mask_bits(ptr, _mask, _bits)	\
+#define set_mask_bits(ptr, mask, bits)	\
 ({								\
-	const typeof(*ptr) mask = (_mask), bits = (_bits);	\
-	typeof(*ptr) old, new;					\
+	const typeof(*(ptr)) mask__ = (mask), bits__ = (bits);	\
+	typeof(*(ptr)) old__, new__;				\
 								\
 	do {							\
-		old = READ_ONCE(*ptr);			\
-		new = (old & ~mask) | bits;			\
-	} while (cmpxchg(ptr, old, new) != old);		\
+		old__ = READ_ONCE(*(ptr));			\
+		new__ = (old__ & ~mask__) | bits__;		\
+	} while (cmpxchg(ptr, old__, new__) != old__);		\
 								\
-	new;							\
+	new__;							\
 })
 #endif