int ovl_permission(struct inode *inode, int mask)
{
struct ovl_entry *oe;
struct dentry *alias = NULL;
struct inode *realinode;
struct dentry *realdentry;
bool is_upper;
int err;
if (S_ISDIR(inode->i_mode)) {
oe = inode->i_private;
} else if (mask & MAY_NOT_BLOCK) {
return -ECHILD;
} else {
/*
* For non-directories find an alias and get the info
* from there.
*/
alias = d_find_any_alias(inode);
if (WARN_ON(!alias))
return -ENOENT;
oe = alias->d_fsdata;
}
realdentry = ovl_entry_real(oe, &is_upper);
/* Careful in RCU walk mode */
realinode = ACCESS_ONCE(realdentry->d_inode);
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
err = -ENOENT;
goto out_dput;
}
if (mask & MAY_WRITE) {
umode_t mode = realinode->i_mode;
/*
* Writes will always be redirected to upper layer, so
* ignore lower layer being read-only.
*
* If the overlay itself is read-only then proceed
* with the permission check, don't return EROFS.
* This will only happen if this is the lower layer of
* another overlayfs.
*
* If upper fs becomes read-only after the overlay was
* constructed return EROFS to prevent modification of
* upper layer.
*/
err = -EROFS;
if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
goto out_dput;
}
err = __inode_permission(realinode, mask);
out_dput:
dput(alias);
return err;
}
int ovl_permission(struct inode *inode, int mask)
{
struct ovl_entry *oe;
struct dentry *alias = NULL;
struct inode *realinode;
struct dentry *realdentry;
bool is_upper;
int err;
if (S_ISDIR(inode->i_mode)) {
oe = inode->i_private;
} else if (mask & MAY_NOT_BLOCK) {
return -ECHILD;
} else {
/*
* For non-directories find an alias and get the info
* from there.
*/
spin_lock(&inode->i_lock);
if (WARN_ON(list_empty(&inode->i_dentry))) {
spin_unlock(&inode->i_lock);
return -ENOENT;
}
alias = list_entry(inode->i_dentry.next,
struct dentry, d_alias);
dget(alias);
spin_unlock(&inode->i_lock);
oe = alias->d_fsdata;
}
realdentry = ovl_entry_real(oe, &is_upper);
/* Careful in RCU walk mode */
realinode = ACCESS_ONCE(realdentry->d_inode);
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
err = -ENOENT;
goto out_dput;
}
if (mask & MAY_WRITE) {
umode_t mode = realinode->i_mode;
/*
* Writes will always be redirected to upper layer, so
* ignore lower layer being read-only.
*
* If the overlay itself is read-only then proceed
* with the permission check, don't return EROFS.
* This will only happen if this is the lower layer of
* another overlayfs.
*
* If upper fs becomes read-only after the overlay was
* constructed return EROFS to prevent modification of
* upper layer.
*/
err = -EROFS;
if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
goto out_dput;
/*
* Nobody gets write access to an immutable file.
*/
err = -EACCES;
if (IS_IMMUTABLE(realinode))
goto out_dput;
}
if (realinode->i_op->permission)
err = realinode->i_op->permission(realinode, mask);
else
err = generic_permission(realinode, mask);
if (!err)
err = devcgroup_inode_permission(realinode, mask);
if (!err)
err = security_inode_permission(realinode, mask);
out_dput:
dput(alias);
return err;
}
