[PATCH Xenial SRU] UBUNTU: zfs: Fix user namespaces uid/gid mapping

[Colin Ian King]

On 06/05/16 14:13, tim.gardner at canonical.com wrote:
> From: Brian Behlendorf <behlendorf1 at llnl.gov>
> 
> BugLink: http://bugs.launchpad.net/bugs/1567558
> 
> Cherry-picked from 874bd959f4f15b3d4b007160ee7ad3f4111dd341 ('Fix user
> namespaces uid/gid mapping')
> https://github.com/zfsonlinux/zfs.git
> 
> As described in torvalds/linux at 5f3a4a2 the &init_user_ns, and
> not the current user_ns, should be passed to posix_acl_from_xattr()
> and posix_acl_to_xattr().  Conveniently the init_user_ns is
> available through the init credential (kcred).
> 
> Signed-off-by: Brian Behlendorf <behlendorf1 at llnl.gov>
> Signed-off-by: Massimo Maggi <me at massimo-maggi.eu>
> Closes #4177
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
> ---
>  zfs/include/linux/xattr_compat.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/zfs/include/linux/xattr_compat.h b/zfs/include/linux/xattr_compat.h
> index eee6c1f..5e19ea1 100644
> --- a/zfs/include/linux/xattr_compat.h
> +++ b/zfs/include/linux/xattr_compat.h
> @@ -190,20 +190,20 @@ fn(struct inode *ip, const char *name, const void *buffer,		\
>  
>  /*
>   * Linux 3.7 API change. posix_acl_{from,to}_xattr gained the user_ns
> - * parameter.  For the HAVE_POSIX_ACL_FROM_XATTR_USERNS version the
> - * userns _may_ not be correct because it's used outside the RCU.
> + * parameter.  All callers are expected to pass the &init_user_ns which
> + * is available through the init credential (kcred).
>   */
>  #ifdef HAVE_POSIX_ACL_FROM_XATTR_USERNS
>  static inline struct posix_acl *
>  zpl_acl_from_xattr(const void *value, int size)
>  {
> -	return (posix_acl_from_xattr(CRED()->user_ns, value, size));
> +	return (posix_acl_from_xattr(kcred->user_ns, value, size));
>  }
>  
>  static inline int
>  zpl_acl_to_xattr(struct posix_acl *acl, void *value, int size)
>  {
> -	return (posix_acl_to_xattr(CRED()->user_ns, acl, value, size));
> +	return (posix_acl_to_xattr(kcred->user_ns, acl, value, size));
>  }
>  
>  #else
> 
Sane fix from the ZFS repo, which also implies it has been tested
thoroughly before landing there.

Looks good to me.

Acked-by: Colin Ian King <colin.king at canonical.com>