fs: port ->setattr() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

3 files changed, 7 insertions, 6 deletions

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index f02e609460e2..e5a6a3bb1209 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -779,10 +779,11 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
 	evm_update_evmxattr(dentry, xattr_name, NULL, 0);
 }
 
-static int evm_attr_change(struct user_namespace *mnt_userns,
+static int evm_attr_change(struct mnt_idmap *idmap,
 			   struct dentry *dentry, struct iattr *attr)
 {
 	struct inode *inode = d_backing_inode(dentry);
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	unsigned int ia_valid = attr->ia_valid;
 
 	if (!i_uid_needs_update(mnt_userns, attr, inode) &&
@@ -800,7 +801,7 @@ static int evm_attr_change(struct user_namespace *mnt_userns,
  * Permit update of file attributes when files have a valid EVM signature,
  * except in the case of them having an immutable portable signature.
  */
-int evm_inode_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		      struct iattr *attr)
 {
 	unsigned int ia_valid = attr->ia_valid;
@@ -827,7 +828,7 @@ int evm_inode_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 		return 0;
 
 	if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
-	    !evm_attr_change(mnt_userns, dentry, attr))
+	    !evm_attr_change(idmap, dentry, attr))
 		return 0;
 
 	integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index 8a9db7dfca7e..9b907c2fee60 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -228,7 +228,7 @@ static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
 		newattrs.ia_valid = ATTR_MODE;
 		inode = evm_xattrs->d_inode;
 		inode_lock(inode);
-		err = simple_setattr(&init_user_ns, evm_xattrs, &newattrs);
+		err = simple_setattr(&nop_mnt_idmap, evm_xattrs, &newattrs);
 		inode_unlock(inode);
 		if (!err)
 			err = count;
diff --git a/security/security.c b/security/security.c
index d1571900a8c7..fceab8e0ff87 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1354,7 +1354,7 @@ int security_inode_permission(struct inode *inode, int mask)
 	return call_int_hook(inode_permission, 0, inode, mask);
 }
 
-int security_inode_setattr(struct user_namespace *mnt_userns,
+int security_inode_setattr(struct mnt_idmap *idmap,
 			   struct dentry *dentry, struct iattr *attr)
 {
 	int ret;
@@ -1364,7 +1364,7 @@ int security_inode_setattr(struct user_namespace *mnt_userns,
 	ret = call_int_hook(inode_setattr, 0, dentry, attr);
 	if (ret)
 		return ret;
-	return evm_inode_setattr(mnt_userns, dentry, attr);
+	return evm_inode_setattr(idmap, dentry, attr);
 }
 EXPORT_SYMBOL_GPL(security_inode_setattr);