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Commit b581755b authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

ovl: xattr filter fix 



a) ovl_need_xattr_filter() is wrong, we can have multiple lower layers
overlaid, all of which (except the lowest one) honouring the
"trusted.overlay.opaque" xattr.  So need to filter everything except the
bottom and the pure-upper layer.

b) we no longer can assume that inode is attached to dentry in
get/setxattr.

This patch unconditionally filters private xattrs to fix both of the above.
Performance impact for get/removexattrs is likely in the noise.

For listxattrs it might be measurable in pathological cases, but I very
much hope nobody cares.  If they do, we'll fix it then.

Reported-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Fixes: b9680917 ("security_d_instantiate(): move to the point prior to attaching dentry to inode")
parent af8c34ce

fs/overlayfs/inode.c

+6 −20
Original line number Diff line number Diff line
@@ -238,41 +238,27 @@ int ovl_setxattr(struct dentry *dentry, struct inode *inode, 
	return err;

}



static bool ovl_need_xattr_filter(struct dentry *dentry,

				  enum ovl_path_type type)

{

	if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER)

		return S_ISDIR(dentry->d_inode->i_mode);

	else

		return false;

}



ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,

		     const char *name, void *value, size_t size)

{

	struct path realpath;

	enum ovl_path_type type = ovl_path_real(dentry, &realpath);

	struct dentry *realdentry = ovl_dentry_real(dentry);



	if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))

	if (ovl_is_private_xattr(name))

		return -ENODATA;



	return vfs_getxattr(realpath.dentry, name, value, size);

	return vfs_getxattr(realdentry, name, value, size);

}



ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)

{

	struct path realpath;

	enum ovl_path_type type = ovl_path_real(dentry, &realpath);

	struct dentry *realdentry = ovl_dentry_real(dentry);

	ssize_t res;

	int off;



	res = vfs_listxattr(realpath.dentry, list, size);

	res = vfs_listxattr(realdentry, list, size);

	if (res <= 0 || size == 0)

		return res;



	if (!ovl_need_xattr_filter(dentry, type))

		return res;



	/* filter out private xattrs */

	for (off = 0; off < res;) {

		char *s = list + off;
@@ -302,7 +288,7 @@ int ovl_removexattr(struct dentry *dentry, const char *name) 
		goto out;



	err = -ENODATA;

	if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))

	if (ovl_is_private_xattr(name))

		goto out_drop_write;



	if (!OVL_TYPE_UPPER(type)) {