Re: Small security bug with misconfigured access rights

["Jordan Russell" <jr-list-kernel@quo.to>]

Giuliano Pochini wrote:
> Well, I don't know if it is really a bug.
>
> Create a directory like this:
>
> # ls -la
> total 12
> drwxr-sr-x   2 pochini  root         4096 Nov 28 16:33 .
> drwxr-xr-x  32 pochini  users        8192 Nov 28 16:25 ..
>
> Sgid bit is set and the directory is owned by me and the
> group is root (yes, it shouldn't be).
>
> When I create a file here, it gets the root group even
> if I don't belong to it.

That's the correct behavior. Quoting "man mount":

       grpid or bsdgroups / nogrpid or sysvgroups
              These options define what group id a newly  created  file
gets.   When
              grpid  is  set,  it  takes the group id of the directory in
which it is
              created; otherwise (the default) it takes the fsgid of the
current pro-
              cess,  unless  the  directory  has the setgid bit set, in
which case it
              takes the gid from the parent directory, and also gets the
setgid  bit
              set if it is a directory itself.


Jordan Russell