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vfs: add vfs_get_link() helper 

This helper is for filesystems that want to read the symlink and are better
off with the get_link() interface (returning a char *) rather than the
readlink() interface (copy into a userspace buffer).

Also call the LSM hook for readlink (not get_link) since this is for
symlink reading not following.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2016-10-04 14:40:45 +02:00
parent 78a3fa4f32
commit d60874cd58
2 changed files with 26 additions and 0 deletions
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25
fs/namei.c
View File

@ -4677,6 +4677,31 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
}
EXPORT_SYMBOL(generic_readlink);
/**
* vfs_get_link - get symlink body
* @dentry: dentry on which to get symbolic link
* @done: caller needs to free returned data with this
*
* Calls security hook and i_op->get_link() on the supplied inode.
*
* It does not touch atime. That's up to the caller if necessary.
*
* Does not work on "special" symlinks like /proc/$$/fd/N
*/
const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
{
const char *res = ERR_PTR(-EINVAL);
struct inode *inode = d_inode(dentry);
if (d_is_symlink(dentry)) {
res = ERR_PTR(security_inode_readlink(dentry));
if (!res)
res = inode->i_op->get_link(dentry, inode, done);
}
return res;
}
EXPORT_SYMBOL(vfs_get_link);
/* get the link contents into pagecache */
const char *page_get_link(struct dentry *dentry, struct inode *inode,
struct delayed_call *callback)

1
include/linux/fs.h
View File

@ -2919,6 +2919,7 @@ extern int vfs_stat(const char __user *, struct kstat *);
extern int vfs_lstat(const char __user *, struct kstat *);
extern int vfs_fstat(unsigned int, struct kstat *);
extern int vfs_fstatat(int , const char __user *, struct kstat *, int);
extern const char *vfs_get_link(struct dentry *, struct delayed_call *);
extern int __generic_block_fiemap(struct inode *inode,
struct fiemap_extent_info *fieinfo,