Commit 5436ab0a authored by Amir Goldstein's avatar Amir Goldstein
Browse files

ovl: implement lookup in data-only layers 



Lookup in data-only layers only for a lower metacopy with an absolute
redirect xattr.

The metacopy xattr is not checked on files found in the data-only layers
and redirect xattr are not followed in the data-only layers.

Reviewed-by: default avatarAlexander Larsson <alexl@redhat.com>
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 37ebf056

fs/overlayfs/namei.c

+72 −1
Original line number Diff line number Diff line
@@ -14,6 +14,8 @@ 
#include <linux/exportfs.h>

#include "overlayfs.h"



#include "../internal.h"	/* for vfs_path_lookup */



struct ovl_lookup_data {

	struct super_block *sb;

	struct vfsmount *mnt;
@@ -24,6 +26,8 @@ struct ovl_lookup_data { 
	bool last;

	char *redirect;

	bool metacopy;

	/* Referring to last redirect xattr */

	bool absolute_redirect;

};



static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d,
@@ -33,11 +37,13 @@ static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d 
	char *buf;

	struct ovl_fs *ofs = OVL_FS(d->sb);



	d->absolute_redirect = false;

	buf = ovl_get_redirect_xattr(ofs, path, prelen + strlen(post));

	if (IS_ERR_OR_NULL(buf))

		return PTR_ERR(buf);



	if (buf[0] == '/') {

		d->absolute_redirect = true;

		/*

		 * One of the ancestor path elements in an absolute path

		 * lookup in ovl_lookup_layer() could have been opaque and
@@ -349,6 +355,61 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d, 
	return 0;

}



static int ovl_lookup_data_layer(struct dentry *dentry, const char *redirect,

				 const struct ovl_layer *layer,

				 struct path *datapath)

{

	int err;



	err = vfs_path_lookup(layer->mnt->mnt_root, layer->mnt, redirect,

			LOOKUP_BENEATH | LOOKUP_NO_SYMLINKS | LOOKUP_NO_XDEV,

			datapath);

	pr_debug("lookup lowerdata (%pd2, redirect=\"%s\", layer=%d, err=%i)\n",

		 dentry, redirect, layer->idx, err);



	if (err)

		return err;



	err = -EREMOTE;

	if (ovl_dentry_weird(datapath->dentry))

		goto out_path_put;



	err = -ENOENT;

	/* Only regular file is acceptable as lower data */

	if (!d_is_reg(datapath->dentry))

		goto out_path_put;



	return 0;



out_path_put:

	path_put(datapath);



	return err;

}



/* Lookup in data-only layers by absolute redirect to layer root */

static int ovl_lookup_data_layers(struct dentry *dentry, const char *redirect,

				  struct ovl_path *lowerdata)

{

	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);

	const struct ovl_layer *layer;

	struct path datapath;

	int err = -ENOENT;

	int i;



	layer = &ofs->layers[ofs->numlayer - ofs->numdatalayer];

	for (i = 0; i < ofs->numdatalayer; i++, layer++) {

		err = ovl_lookup_data_layer(dentry, redirect, layer, &datapath);

		if (!err) {

			mntput(datapath.mnt);

			lowerdata->dentry = datapath.dentry;

			lowerdata->layer = layer;

			return 0;

		}

	}



	return err;

}



int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,

			struct dentry *upperdentry, struct ovl_path **stackp)
@@ -917,7 +978,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, 


		if (!ofs->config.redirect_follow)

			d.last = i == ovl_numlower(poe) - 1;

		else

		else if (d.is_dir || !ofs->numdatalayer)

			d.last = lower.layer->idx == ovl_numlower(roe);



		d.mnt = lower.layer->mnt;
@@ -1011,6 +1072,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, 
		}

	}



	/* Lookup absolute redirect from lower metacopy in data-only layers */

	if (d.metacopy && ctr && ofs->numdatalayer && d.absolute_redirect) {

		err = ovl_lookup_data_layers(dentry, d.redirect,

					     &stack[ctr]);

		if (!err) {

			d.metacopy = false;

			ctr++;

		}

	}



	/*

	 * For regular non-metacopy upper dentries, there is no lower

	 * path based lookup, hence ctr will be zero. If a dentry is found