fs: port ->get_acl() 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>

12 files changed, 29 insertions, 26 deletions

diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index 429b8e4a6284..d42d7b8de2f5 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -84,7 +84,7 @@ prototypes::
 	int (*fileattr_set)(struct user_namespace *mnt_userns,
 			    struct dentry *dentry, struct fileattr *fa);
 	int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa);
-	struct posix_acl * (*get_acl)(struct user_namespace *, struct dentry *, int);
+	struct posix_acl * (*get_acl)(struct mnt_idmap *, struct dentry *, int);
 
 locking rules:
 	all may block
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 3fcadfcf4e3a..056e446c70e0 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -443,7 +443,7 @@ As of kernel 2.6.22, the following members are defined:
 		int (*atomic_open)(struct inode *, struct dentry *, struct file *,
 				   unsigned open_flag, umode_t create_mode);
 		int (*tmpfile) (struct mnt_idmap *, struct inode *, struct file *, umode_t);
-		struct posix_acl * (*get_acl)(struct user_namespace *, struct dentry *, int);
+		struct posix_acl * (*get_acl)(struct mnt_idmap *, struct dentry *, int);
 	        int (*set_acl)(struct user_namespace *, struct dentry *, struct posix_acl *, int);
 		int (*fileattr_set)(struct user_namespace *mnt_userns,
 				    struct dentry *dentry, struct fileattr *fa);
diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 9848a245fa6f..cfd4545f2d02 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -139,7 +139,7 @@ struct posix_acl *v9fs_iop_get_inode_acl(struct inode *inode, int type, bool rcu
 
 }
 
-struct posix_acl *v9fs_iop_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *v9fs_iop_get_acl(struct mnt_idmap *idmap,
 				   struct dentry *dentry, int type)
 {
 	struct v9fs_session_info *v9ses;
diff --git a/fs/9p/acl.h b/fs/9p/acl.h
index 4c60a2bce5de..e0e58967d916 100644
--- a/fs/9p/acl.h
+++ b/fs/9p/acl.h
@@ -10,7 +10,7 @@
 int v9fs_get_acl(struct inode *inode, struct p9_fid *fid);
 struct posix_acl *v9fs_iop_get_inode_acl(struct inode *inode, int type,
 				   bool rcu);
-struct posix_acl *v9fs_iop_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *v9fs_iop_get_acl(struct mnt_idmap *idmap,
 					  struct dentry *dentry, int type);
 int v9fs_iop_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		     struct posix_acl *acl, int type);
diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index bbf58c2439da..1fae9b60e48f 100644
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -1674,7 +1674,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 	return rc;
 }
 
-struct posix_acl *cifs_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *cifs_get_acl(struct mnt_idmap *idmap,
 			       struct dentry *dentry, int type)
 {
 #if defined(CONFIG_CIFS_ALLOW_INSECURE_LEGACY) && defined(CONFIG_CIFS_POSIX)
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 1207b39686fb..aeae6544cdd8 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -225,7 +225,7 @@ extern struct cifs_ntsd *get_cifs_acl(struct cifs_sb_info *, struct inode *,
 				      const char *, u32 *, u32);
 extern struct cifs_ntsd *get_cifs_acl_by_fid(struct cifs_sb_info *,
 				const struct cifs_fid *, u32 *, u32);
-extern struct posix_acl *cifs_get_acl(struct user_namespace *mnt_userns,
+extern struct posix_acl *cifs_get_acl(struct mnt_idmap *idmap,
 				      struct dentry *dentry, int type);
 extern int cifs_set_acl(struct user_namespace *mnt_userns,
 			struct dentry *dentry, struct posix_acl *acl, int type);
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index cf85901d7a5d..8487ac0cc239 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -1122,10 +1122,10 @@ static int ecryptfs_fileattr_set(struct user_namespace *mnt_userns,
 	return rc;
 }
 
-static struct posix_acl *ecryptfs_get_acl(struct user_namespace *mnt_userns,
+static struct posix_acl *ecryptfs_get_acl(struct mnt_idmap *idmap,
 					  struct dentry *dentry, int type)
 {
-	return vfs_get_acl(mnt_userns, ecryptfs_dentry_to_lower(dentry),
+	return vfs_get_acl(idmap, ecryptfs_dentry_to_lower(dentry),
 			   posix_acl_xattr_name(type));
 }
 
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index ad33253ed7e9..3ea4fc54f469 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -515,14 +515,16 @@ struct posix_acl *ovl_get_acl_path(const struct path *path,
 {
 	struct posix_acl *real_acl, *clone;
 	struct user_namespace *mnt_userns;
+	struct mnt_idmap *idmap;
 	struct inode *realinode = d_inode(path->dentry);
 
-	mnt_userns = mnt_user_ns(path->mnt);
+	idmap = mnt_idmap(path->mnt);
+	mnt_userns = mnt_idmap_owner(idmap);
 
 	if (noperm)
 		real_acl = get_inode_acl(realinode, posix_acl_type(acl_name));
 	else
-		real_acl = vfs_get_acl(mnt_userns, path->dentry, acl_name);
+		real_acl = vfs_get_acl(idmap, path->dentry, acl_name);
 	if (IS_ERR_OR_NULL(real_acl))
 		return real_acl;
 
@@ -555,7 +557,7 @@ struct posix_acl *ovl_get_acl_path(const struct path *path,
  *
  * This is obviously only relevant when idmapped layers are used.
  */
-struct posix_acl *do_ovl_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *do_ovl_get_acl(struct mnt_idmap *idmap,
 				 struct inode *inode, int type,
 				 bool rcu, bool noperm)
 {
@@ -618,7 +620,7 @@ static int ovl_set_or_remove_acl(struct dentry *dentry, struct inode *inode,
 
 		ovl_path_lower(dentry, &realpath);
 		old_cred = ovl_override_creds(dentry->d_sb);
-		real_acl = vfs_get_acl(mnt_user_ns(realpath.mnt), realdentry,
+		real_acl = vfs_get_acl(mnt_idmap(realpath.mnt), realdentry,
 				       acl_name);
 		revert_creds(old_cred);
 		if (IS_ERR(real_acl)) {
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index b6e17f631b53..1e8b0be85e4b 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -610,18 +610,18 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 
 #ifdef CONFIG_FS_POSIX_ACL
-struct posix_acl *do_ovl_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *do_ovl_get_acl(struct mnt_idmap *idmap,
 				 struct inode *inode, int type,
 				 bool rcu, bool noperm);
 static inline struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type,
 						  bool rcu)
 {
-	return do_ovl_get_acl(&init_user_ns, inode, type, rcu, true);
+	return do_ovl_get_acl(&nop_mnt_idmap, inode, type, rcu, true);
 }
-static inline struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
+static inline struct posix_acl *ovl_get_acl(struct mnt_idmap *idmap,
 					    struct dentry *dentry, int type)
 {
-	return do_ovl_get_acl(mnt_userns, d_inode(dentry), type, false, false);
+	return do_ovl_get_acl(idmap, d_inode(dentry), type, false, false);
 }
 int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		struct posix_acl *acl, int type);
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index d7bc81fc0840..17e141a94671 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -111,7 +111,7 @@ void forget_all_cached_acls(struct inode *inode)
 }
 EXPORT_SYMBOL(forget_all_cached_acls);
 
-static struct posix_acl *__get_acl(struct user_namespace *mnt_userns,
+static struct posix_acl *__get_acl(struct mnt_idmap *idmap,
 				   struct dentry *dentry, struct inode *inode,
 				   int type)
 {
@@ -154,7 +154,7 @@ static struct posix_acl *__get_acl(struct user_namespace *mnt_userns,
 	 * we'll just create the negative cache entry.
 	 */
 	if (dentry && inode->i_op->get_acl) {
-		acl = inode->i_op->get_acl(mnt_userns, dentry, type);
+		acl = inode->i_op->get_acl(idmap, dentry, type);
 	} else if (inode->i_op->get_inode_acl) {
 		acl = inode->i_op->get_inode_acl(inode, type, false);
 	} else {
@@ -181,7 +181,7 @@ static struct posix_acl *__get_acl(struct user_namespace *mnt_userns,
 
 struct posix_acl *get_inode_acl(struct inode *inode, int type)
 {
-	return __get_acl(&init_user_ns, NULL, inode, type);
+	return __get_acl(&nop_mnt_idmap, NULL, inode, type);
 }
 EXPORT_SYMBOL(get_inode_acl);
 
@@ -1121,7 +1121,7 @@ EXPORT_SYMBOL_GPL(vfs_set_acl);
 
 /**
  * vfs_get_acl - get posix acls
- * @mnt_userns: user namespace of the mount
+ * @idmap: idmap of the mount
  * @dentry: the dentry based on which to retrieve the posix acls
  * @acl_name: the name of the posix acl
  *
@@ -1130,9 +1130,10 @@ EXPORT_SYMBOL_GPL(vfs_set_acl);
  *
  * Return: On success POSIX ACLs in VFS format, on error negative errno.
  */
-struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *acl_name)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct inode *inode = d_inode(dentry);
 	struct posix_acl *acl;
 	int acl_type, error;
@@ -1154,7 +1155,7 @@ struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
 	if (S_ISLNK(inode->i_mode))
 		return ERR_PTR(-EOPNOTSUPP);
 
-	acl = __get_acl(mnt_userns, dentry, inode, acl_type);
+	acl = __get_acl(idmap, dentry, inode, acl_type);
 	if (IS_ERR(acl))
 		return acl;
 	if (!acl)
@@ -1256,7 +1257,7 @@ ssize_t do_get_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 	ssize_t error;
 	struct posix_acl *acl;
 
-	acl = vfs_get_acl(mnt_idmap_owner(idmap), dentry, acl_name);
+	acl = vfs_get_acl(idmap, dentry, acl_name);
 	if (IS_ERR(acl))
 		return PTR_ERR(acl);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4855fd071bf8..31a714377ba2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2164,7 +2164,7 @@ struct inode_operations {
 			   umode_t create_mode);
 	int (*tmpfile) (struct mnt_idmap *, struct inode *,
 			struct file *, umode_t);
-	struct posix_acl *(*get_acl)(struct user_namespace *, struct dentry *,
+	struct posix_acl *(*get_acl)(struct mnt_idmap *, struct dentry *,
 				     int);
 	int (*set_acl)(struct user_namespace *, struct dentry *,
 		       struct posix_acl *, int);
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index ee608d22ecb9..042ef62f9276 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -102,7 +102,7 @@ static inline void cache_no_acl(struct inode *inode)
 
 int vfs_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		const char *acl_name, struct posix_acl *kacl);
-struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *acl_name);
 int vfs_remove_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		   const char *acl_name);
@@ -141,7 +141,7 @@ static inline int vfs_set_acl(struct user_namespace *mnt_userns,
 	return -EOPNOTSUPP;
 }
 
-static inline struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
+static inline struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap,
 					    struct dentry *dentry,
 					    const char *acl_name)
 {