However, with is_superuser it does not grant any file owner to change the ownership. Only a few users can be given a superuser role according to FSAL implementation. - Sriram From: Sriram Patil <sriramp@vmware.com> Date: Wednesday, March 11, 2020 at 11:40 AM To: Frank Filz <ffilzlnx@mindspring.com>, Deepthi Shivaramu <des@vmware.com>, "devel@lists.nfs-ganesha.org" <devel@lists.nfs-ganesha.org> Subject: Re: [NFS-Ganesha-Devel] Re: chown on a file with 777 permission does not work for any non-root user, not even the owner of the file We also have a way of achieving this in ganesha with the help of “is_superuser” FSAL API. - Sriram From: Frank Filz <ffilzlnx@mindspring.com> Date: Wednesday, March 11, 2020 at 9:45 AM To: Deepthi Shivaramu <des@vmware.com>, "devel@lists.nfs-ganesha.org" <devel@lists.nfs-ganesha.org> Subject: [NFS-Ganesha-Devel] Re: chown on a file with 777 permission does not work for any non-root user, not even the owner of the file Is there some documentation on how this works on other servers you can point us to? I wasn’t aware this was allowed outside the context of ACLs, though obviously if you can allow the action with ACLs, there might be a case for allowing it otherwise, though ACLs allow it on a per-file basis (and Windows only allows an administrator to set “take ownership” flag on a file so the user can take ownership of a file as opposed to the administrator changing the ownership). Frank From: Deepthi Shivaramu [mailto:des@vmware.com] Sent: Wednesday, March 11, 2020 8:08 AM To: Frank Filz <ffilzlnx@mindspring.com>; devel@lists.nfs-ganesha.org Subject: [NFS-Ganesha-Devel] Re: chown on a file with 777 permission does not work for any non-root user, not even the owner of the file Frank, Thanks for the reply. I got your point. Most of the enterprise NFS servers provide a hook to allow chown by non root users. Can we implement a hook which when set allow NFSv3 setattr by non root to change owner of the file when file has write permission. ACLs are anyway a solution with NFSv4. regards, Deepthi On 11 Mar 2020 19:55, Frank Filz <ffilzlnx@mindspring.com<mailto:ffilzlnx@mindspring.com>> wrote:
I have NFSv3 mount on linux client and trying to change the owner of the file:
[root@sc-rdops-vm07-dhcp-212-202 mnt]# ls -la new.txt -rwxrwxrwx. 1 testu2 testg2 7 Mar 11 04:00 new.txt [root@sc-rdops-vm07-dhcp-212-202 mnt]# su testu2 [testu2@sc-rdops-vm07-dhcp-212-202 mnt]$ id uid=2222(testu2) gid=8888(testg2) groups=8888(testg2) [testu2@sc-rdops-vm07-dhcp-212-202 mnt]$ [testu2@sc-rdops-vm07-dhcp-212-202 mnt]$ chown testu1 new.txt chown: changing ownership of ‘new.txt’: Operation not permitted [testu2@sc-rdops-vm07-dhcp-212-202 mnt]$ [root@sc-rdops-vm07-dhcp-212-202 mnt]# su testu1 [testu1@sc-rdops-vm07-dhcp-212-202 mnt]$ id uid=1111(testu1) gid=8888(testg2) groups=8888(testg2) [testu1@sc-rdops-vm07-dhcp-212-202 mnt]$ [testu1@sc-rdops-vm07-dhcp-212-202 mnt]$ chown testu1 new.txt chown: changing ownership of ‘new.txt’: Operation not permitted [testu1@sc-rdops-vm07-dhcp-212-202 mnt]$
The file belongs to testu2 and when I try to change the owner to testu1 logged in as testu2, it hits this error :
2020-03-11T11:12:08Z : epoch 5e5f8af3 : vdfsops0aa0d27c.vsanfs-sh.prv : ganesha.nfsd-50332[::ffff:10.160.212.202] [svc_46] 354 :fsal_check_setattr_perms :FSAL :Access check returned Forbidden action (new OWNER was not user)
if (FSAL_TEST_MASK(attr->valid_mask, ATTR_OWNER)) { /* non-root is only allowed to "take ownership of file" */ . <--- It says owner of file cannot change the ownership to someone else. Someone else needs to take ownership. if (attr->owner != creds->caller_uid) { status = fsalstat(ERR_FSAL_PERM, 0); note = " (new OWNER was not user)"; goto out; }
So I login as non-owner, testu1 and try chown, it proceeds from this check but fails here:
2020-03-11T11:11:01Z : epoch 5e5f8af3 : vdfsops0aa0d27c.vsanfs-sh.prv : ganesha.nfsd-50332[::ffff:10.160.212.202] [svc_41] 354 :fsal_check_setattr_perms :FSAL :Access check returned Forbidden action (no ACL to check)
if (current->acl) { status = obj->obj_ops->test_access(obj, access_check, NULL, NULL, false); note = " (checked ACL)"; goto out; }
if (access_check != FSAL_ACE4_MASK_SET(FSAL_ACE_PERM_WRITE_DATA)) { /* Without an ACL, this user is not allowed some operation */ status = fsalstat(ERR_FSAL_PERM, 0); note = " (no ACL to check)"; goto out; }
access_check variable starts with 0 and we put in only FSAL_ACE_PERM_WRITE_OWNER in first block for chown case. So obviously it does not contain FSAL_ACE_PERM_WRITE_DATA which we are checking here. So how do we expect this to proceed? We do not support ACLs yet and anyway this is NFSv3 case, I believe we should not have any dependency on ACL support for this usecase.
In POSIX systems, only root can change ownership of files (and owner of a file may change the group owner of the file to one of that user's groups). Of course in Linux a non-root user MIGHT be given a CAP to allow it to change ownership, but NFS is not really set up to deal with CAPs. Only with NFSv4 ACLs or RichACLs are non-root users allowed to change ownership of files. Frank