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ext4: atomically set inode->i_flags in ext4_set_inode_flags()

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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
This commit is contained in:
Theodore Ts'o 2014-03-24 14:43:12 -04:00
parent ed3654eb98
commit 5f16f3225b
3 changed files with 42 additions and 6 deletions
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3
include/linux/fs.h
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@ -2556,6 +2556,9 @@ static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
void inode_dio_wait(struct inode *inode);
void inode_dio_done(struct inode *inode);
extern void inode_set_flags(struct inode *inode, unsigned int flags,
unsigned int mask);
extern const struct file_operations generic_ro_fops;
#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))