Re: [RFC v2 0/3] VFS/NFS support to destroy FS credentials

[Jeff Layton <jlayton@redhat.com>]

On Fri, 2017-08-04 at 10:49 -0400, Olga Kornievskaia wrote:
> Allow a user to call into the file system and ask to destroy FS
> credentials. For instance, when the user logs out after using
> a kerberized NFS share, he destroys Kerberos credentials but NFS
> credentials remain valid until the gss context expires. Allow
> the user (or things like pam) to trigger destruction of such
> credentials.
> 
> A userland application would do:
> 
> fd = open("/mnt", O_DIRECTORY|O_RDONLY);
> syscall(_NR_destroy_creds, fd);
> 
> v2: fixing a hasty IS_DIR check, definition of __NR_destroy_creds
> and order of the patches
>  
> Olga Kornievskaia (3):
>   VFS adding destroy_creds call
>   SUNRPC mark user credentials destroyed
>   NFS define vfs destroy_creds functions
> 
>  arch/x86/entry/syscalls/syscall_32.tbl |  1 +
>  arch/x86/entry/syscalls/syscall_64.tbl |  1 +
>  fs/nfs/dir.c                           |  8 ++++++++
>  fs/read_write.c                        | 22 ++++++++++++++++++++++
>  include/linux/fs.h                     |  2 ++
>  include/linux/sunrpc/auth.h            |  5 +++++
>  include/linux/syscalls.h               |  2 +-
>  include/uapi/asm-generic/unistd.h      |  4 +++-
>  kernel/sys_ni.c                        |  1 +
>  net/sunrpc/auth.c                      |  9 +++++++++
>  net/sunrpc/auth_generic.c              | 15 +++++++++++++++
>  net/sunrpc/auth_gss/auth_gss.c         |  3 +++
>  12 files changed, 71 insertions(+), 2 deletions(-)
> 

I think I'd like to see a proposed manpage for this syscall.

How do you expect this syscall to be used by userland? What will call it
and under what circumstances?

Also, this looks at first glance like a single-purpose, single-
filesystem call. Would this have any purpose at all outside of NFS?
Would this be usable with CIFS or Ceph in some fashion?

-- 
Jeff Layton <jlayton@redhat.com>