ovl: use ovl_path_getxattr() wrapper

Add a helper that allows to retrieve ovl xattrs from either lower or
upper layers. To stop passing mnt and dentry separately everywhere use
struct path which more accurately reflects the tight coupling between
mount and dentry in this helper. Swich over all places to pass a path
argument that can operate on either upper or lower layers. This is
needed to support idmapped base layers with overlayfs.

Some helpers are always called with an upper dentry, which is now utilized
by these helpers to create the path.  Make this usage explicit by renaming
the argument to "upperdentry" and by renaming the function as well in some
cases.  Also add a check in ovl_do_getxattr() to catch misuse of these
functions.

Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 55 insertions, 22 deletions

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index e91f0df914f9..6cbb1fd2a4ec 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -218,30 +218,48 @@ static inline int ovl_do_symlink(struct ovl_fs *ofs,
 	return err;
 }
 
-static inline ssize_t ovl_do_getxattr(struct ovl_fs *ofs, struct dentry *dentry,
-				      const char *name, void *value,
-				      size_t size)
+static inline ssize_t ovl_do_getxattr(struct path *path, const char *name,
+				      void *value, size_t size)
 {
-	int err = vfs_getxattr(&init_user_ns, dentry, name, value, size);
-	int len = (value && err > 0) ? err : 0;
+	int err, len;
+
+	WARN_ON(path->dentry->d_sb != path->mnt->mnt_sb);
+
+	err = vfs_getxattr(mnt_user_ns(path->mnt), path->dentry,
+			       name, value, size);
+	len = (value && err > 0) ? err : 0;
 
 	pr_debug("getxattr(%pd2, \"%s\", \"%*pE\", %zu, 0) = %i\n",
-		 dentry, name, min(len, 48), value, size, err);
+		 path->dentry, name, min(len, 48), value, size, err);
 	return err;
 }
 
-static inline ssize_t ovl_getxattr(struct ovl_fs *ofs, struct dentry *dentry,
-				   enum ovl_xattr ox, void *value,
-				   size_t size)
+static inline ssize_t ovl_getxattr_upper(struct ovl_fs *ofs,
+					 struct dentry *upperdentry,
+					 enum ovl_xattr ox, void *value,
+					 size_t size)
+{
+	struct path upperpath = {
+		.dentry = upperdentry,
+		.mnt = ovl_upper_mnt(ofs),
+	};
+
+	return ovl_do_getxattr(&upperpath, ovl_xattr(ofs, ox), value, size);
+}
+
+static inline ssize_t ovl_path_getxattr(struct ovl_fs *ofs,
+					 struct path *path,
+					 enum ovl_xattr ox, void *value,
+					 size_t size)
 {
-	return ovl_do_getxattr(ofs, dentry, ovl_xattr(ofs, ox), value, size);
+	return ovl_do_getxattr(path, ovl_xattr(ofs, ox), value, size);
 }
 
 static inline int ovl_do_setxattr(struct ovl_fs *ofs, struct dentry *dentry,
 				  const char *name, const void *value,
 				  size_t size, int flags)
 {
-	int err = vfs_setxattr(&init_user_ns, dentry, name, value, size, flags);
+	int err = vfs_setxattr(ovl_upper_mnt_userns(ofs), dentry, name, value, size, flags);
 
 	pr_debug("setxattr(%pd2, \"%s\", \"%*pE\", %zu, %d) = %i\n",
 		 dentry, name, min((int)size, 48), value, size, flags, err);
@@ -258,7 +276,7 @@ static inline int ovl_setxattr(struct ovl_fs *ofs, struct dentry *dentry,
 static inline int ovl_do_removexattr(struct ovl_fs *ofs, struct dentry *dentry,
 				     const char *name)
 {
-	int err = vfs_removexattr(&init_user_ns, dentry, name);
+	int err = vfs_removexattr(ovl_upper_mnt_userns(ofs), dentry, name);
 	pr_debug("removexattr(%pd2, \"%s\") = %i\n", dentry, name, err);
 	return err;
 }
@@ -394,9 +412,20 @@ struct file *ovl_path_open(struct path *path, int flags);
 int ovl_copy_up_start(struct dentry *dentry, int flags);
 void ovl_copy_up_end(struct dentry *dentry);
 bool ovl_already_copied_up(struct dentry *dentry, int flags);
-bool ovl_check_origin_xattr(struct ovl_fs *ofs, struct dentry *dentry);
-bool ovl_check_dir_xattr(struct super_block *sb, struct dentry *dentry,
-			 enum ovl_xattr ox);
+bool ovl_path_check_dir_xattr(struct ovl_fs *ofs, struct path *path,
+			      enum ovl_xattr ox);
+bool ovl_path_check_origin_xattr(struct ovl_fs *ofs, struct path *path);
+
+static inline bool ovl_check_origin_xattr(struct ovl_fs *ofs,
+					  struct dentry *upperdentry)
+{
+	struct path upperpath = {
+		.dentry = upperdentry,
+		.mnt = ovl_upper_mnt(ofs),
+	};
+	return ovl_path_check_origin_xattr(ofs, &upperpath);
+}
+
 int ovl_check_setxattr(struct ovl_fs *ofs, struct dentry *upperdentry,
 		       enum ovl_xattr ox, const void *value, size_t size,
 		       int xerr);
@@ -408,10 +437,9 @@ bool ovl_need_index(struct dentry *dentry);
 int ovl_nlink_start(struct dentry *dentry);
 void ovl_nlink_end(struct dentry *dentry);
 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
-int ovl_check_metacopy_xattr(struct ovl_fs *ofs, struct dentry *dentry);
+int ovl_check_metacopy_xattr(struct ovl_fs *ofs, struct path *path);
 bool ovl_is_metacopy_dentry(struct dentry *dentry);
-char *ovl_get_redirect_xattr(struct ovl_fs *ofs, struct dentry *dentry,
-			     int padding);
+char *ovl_get_redirect_xattr(struct ovl_fs *ofs, struct path *path, int padding);
 int ovl_sync_status(struct ovl_fs *ofs);
 
 static inline void ovl_set_flag(unsigned long flag, struct inode *inode)
@@ -430,9 +458,15 @@ static inline bool ovl_test_flag(unsigned long flag, struct inode *inode)
 }
 
 static inline bool ovl_is_impuredir(struct super_block *sb,
-				    struct dentry *dentry)
+				    struct dentry *upperdentry)
 {
-	return ovl_check_dir_xattr(sb, dentry, OVL_XATTR_IMPURE);
+	struct ovl_fs *ofs = OVL_FS(sb);
+	struct path upperpath = {
+		.dentry = upperdentry,
+		.mnt = ovl_upper_mnt(ofs),
+	};
+
+	return ovl_path_check_dir_xattr(ofs, &upperpath, OVL_XATTR_IMPURE);
 }
 
 /*
@@ -659,8 +693,7 @@ int ovl_fileattr_set(struct user_namespace *mnt_userns,
 int ovl_copy_up(struct dentry *dentry);
 int ovl_copy_up_with_data(struct dentry *dentry);
 int ovl_maybe_copy_up(struct dentry *dentry, int flags);
-int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
-		   struct dentry *new);
+int ovl_copy_xattr(struct super_block *sb, struct path *path, struct dentry *new);
 int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upper, struct kstat *stat);
 struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct dentry *real,
 				  bool is_upper);