Re: [PATCH 3/4] libdiskfs: add permission check to file_chflags

[Samuel Thibault]

Hello,

Justus Winter, le Wed 11 Jun 2014 13:41:09 +0200, a écrit :
> @@ -25,6 +25,12 @@ diskfs_S_file_chflags (struct protid *cred,
>  {
>    CHANGE_NODE_FIELD (cred,
>                  ({
> +                     if (flags & 0xffff0000
> +                         && ! idvec_contains (cred->user->uids, 0))
> +                       /* Only root is allowed to change the high 16
> +                          bits.  */
> +                       return EPERM;
> +

Mmm, but if a flag was set by root, then a user shouldn't be allowed to
clear it, I guess.  So it'd probably rather be something like:

if ((flags & 0xffff0000u) != (np->dn_stat.st_flags & 0xffff0000u)) etc.

Note the needed u in the constant, it is unspecified how negative int
are coded.

Samuel