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authorTheodore Ts'o <tytso@mit.edu>2014-03-30 10:20:01 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-03-30 17:02:06 -0700
commit00a1a053ebe5febcfc2ec498bd894f035ad2aa06 (patch)
tree2a6206f1b3d195168cc1d835b459ea99c2db7811 /include
parent981e893ed537cbaa08f8089d480db4165e6d71c0 (diff)
downloadlinux-linaro-stable-00a1a053ebe5febcfc2ec498bd894f035ad2aa06.tar.gz
ext4: atomically set inode->i_flags in ext4_set_inode_flags()
Use cmpxchg() to atomically set i_flags instead of clearing out the S_IMMUTABLE, S_APPEND, etc. flags and then setting them from the EXT4_IMMUTABLE_FL, EXT4_APPEND_FL flags, since this opens up a race where an immutable file has the immutable flag cleared for a brief window of time. Reported-by: John Sullivan <jsrhbz@kanargh.force9.co.uk> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/bitops.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index abc9ca778456..be5fd38bd5a0 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -196,6 +196,21 @@ static inline unsigned long __ffs64(u64 word)
#ifdef __KERNEL__
+#ifndef set_mask_bits
+#define set_mask_bits(ptr, _mask, _bits) \
+({ \
+ const typeof(*ptr) mask = (_mask), bits = (_bits); \
+ typeof(*ptr) old, new; \
+ \
+ do { \
+ old = ACCESS_ONCE(*ptr); \
+ new = (old & ~mask) | bits; \
+ } while (cmpxchg(ptr, old, new) != old); \
+ \
+ new; \
+})
+#endif
+
#ifndef find_last_bit
/**
* find_last_bit - find the last set bit in a memory region