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, 10 insertions, 11 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index b531b5af8c68..714ec569d25b 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -44,9 +44,9 @@ static bool ovl_must_copy_xattr(const char *name)
 	       !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN);
 }
 
-int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
-		   struct dentry *new)
+int ovl_copy_xattr(struct super_block *sb, struct path *oldpath, struct dentry *new)
 {
+	struct dentry *old = oldpath->dentry;
 	ssize_t list_size, size, value_size = 0;
 	char *buf, *name, *value = NULL;
 	int error = 0;
@@ -94,9 +94,9 @@ int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
 			continue; /* Discard */
 		}
 retry:
-		size = vfs_getxattr(&init_user_ns, old, name, value, value_size);
+		size = ovl_do_getxattr(oldpath, name, value, value_size);
 		if (size == -ERANGE)
-			size = vfs_getxattr(&init_user_ns, old, name, NULL, 0);
+			size = ovl_do_getxattr(oldpath, name, NULL, 0);
 
 		if (size < 0) {
 			error = size;
@@ -582,7 +582,7 @@ static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
 			return err;
 	}
 
-	err = ovl_copy_xattr(c->dentry->d_sb, c->lowerpath.dentry, temp);
+	err = ovl_copy_xattr(c->dentry->d_sb, &c->lowerpath, temp);
 	if (err)
 		return err;
 
@@ -873,13 +873,12 @@ static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
 	return true;
 }
 
-static ssize_t ovl_getxattr_value(struct ovl_fs *ofs, struct dentry *dentry,
-				  char *name, char **value)
+static ssize_t ovl_getxattr_value(struct path *path, char *name, char **value)
 {
 	ssize_t res;
 	char *buf;
 
-	res = ovl_do_getxattr(ofs, dentry, name, NULL, 0);
+	res = ovl_do_getxattr(path, name, NULL, 0);
 	if (res == -ENODATA || res == -EOPNOTSUPP)
 		res = 0;
 
@@ -888,7 +887,7 @@ static ssize_t ovl_getxattr_value(struct ovl_fs *ofs, struct dentry *dentry,
 		if (!buf)
 			return -ENOMEM;
 
-		res = ovl_do_getxattr(ofs, dentry, name, buf, res);
+		res = ovl_do_getxattr(path, name, buf, res);
 		if (res < 0)
 			kfree(buf);
 		else
@@ -915,8 +914,8 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
 		return -EIO;
 
 	if (c->stat.size) {
-		err = cap_size = ovl_getxattr_value(ofs, upperpath.dentry,
-						    XATTR_NAME_CAPS, &capability);
+		err = cap_size = ovl_getxattr_value(&upperpath, XATTR_NAME_CAPS,
+						    &capability);
 		if (cap_size < 0)
 			goto out;
 	}