bitops: protect variables in set_mask_bits() macro (18127429) · Commits · 戴 / test

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@redhat.com> Fixes: ("ext4: atomically set inode->i_flags in ext4_set_inode_flags()") Cc: Theodore Ts'o <tytso@mit.edu>

include/linux/bitops.h

+7 −7

Original line number	Diff line number	Diff line
		@@ -236,17 +236,17 @@ static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
		#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

Admin message