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vfs: protect i_nlink

Prevent direct modification of i_nlink by making it const and adding a
non-const __i_nlink alias.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
master
Miklos Szeredi 10 years ago
committed by Christoph Hellwig
parent
commit
a78ef704a8
  1. 2
      fs/inode.c
  2. 20
      include/linux/fs.h

2
fs/inode.c

@ -142,7 +142,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
atomic_set(&inode->i_count, 1);
inode->i_op = &empty_iops;
inode->i_fop = &empty_fops;
inode->i_nlink = 1;
inode->__i_nlink = 1;
inode->i_opflags = 0;
inode->i_uid = 0;
inode->i_gid = 0;

20
include/linux/fs.h

@ -768,7 +768,17 @@ struct inode {
/* Stat data, not accessed from path walking */
unsigned long i_ino;
unsigned int i_nlink;
/*
* Filesystems may only read i_nlink directly. They shall use the
* following functions for modification:
*
* (set|clear|inc|drop)_nlink
* inode_(inc|dec)_link_count
*/
union {
const unsigned int i_nlink;
unsigned int __i_nlink;
};
dev_t i_rdev;
loff_t i_size;
struct timespec i_atime;
@ -1764,7 +1774,7 @@ static inline void mark_inode_dirty_sync(struct inode *inode)
*/
static inline void set_nlink(struct inode *inode, unsigned int nlink)
{
inode->i_nlink = nlink;
inode->__i_nlink = nlink;
}
/**
@ -1777,7 +1787,7 @@ static inline void set_nlink(struct inode *inode, unsigned int nlink)
*/
static inline void inc_nlink(struct inode *inode)
{
inode->i_nlink++;
inode->__i_nlink++;
}
static inline void inode_inc_link_count(struct inode *inode)
@ -1799,7 +1809,7 @@ static inline void inode_inc_link_count(struct inode *inode)
*/
static inline void drop_nlink(struct inode *inode)
{
inode->i_nlink--;
inode->__i_nlink--;
}
/**
@ -1812,7 +1822,7 @@ static inline void drop_nlink(struct inode *inode)
*/
static inline void clear_nlink(struct inode *inode)
{
inode->i_nlink = 0;
inode->__i_nlink = 0;
}
static inline void inode_dec_link_count(struct inode *inode)

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