On 12/30/2009 03:23 PM, [email protected] wrote:
> ------------------------------------------------------
> Subject: prctl: add PR_SET_PROCTITLE_AREA option for prctl()
> From: KOSAKI Motohiro <[email protected]>
>
> Currently glibc2 doesn't have setproctitle(3), so several userland daemons
> attempt to emulate it by doing some brutal stack modifications. This
> works most of the time, but it has problems. For example:
>
> % ps -ef |grep avahi-daemon
> avahi 1679 1 0 09:20 ? 00:00:00 avahi-daemon: running
> [kosadesk.local]
>
> # cat /proc/1679/cmdline
> avahi-daemon: running [kosadesk.local]
>
> This looks good, but the process has also overwritten its environment area
> and made the environ file useless:
>
> # cat /proc/1679/environ
> adesk.local]
>
> Another problem is that the process title length is limited by the size of
> the environment. Security conscious people try to avoid potential
> information leaks by clearing most of the environment before running a
> daemon:
>
> # env - MINIMUM_NEEDED_VAR=foo /path/to/daemon
>
> The resulting environment size may be too small to fit the wanted process
> titles.
>
> This patch makes it possible for userspace to implement setproctitle()
> cleanly. It adds a new PR_SET_PROCTITLE_AREA option for prctl(), which
> updates task's mm_struct->arg_start and arg_end to the given area.
>
Sorry for the late feedback...
On the subject of this patch: would it also make sense to have a prctl()
to give the kernel the address of the "environ" variable, so that
/proc/*/environ can give the *current* environment inside the process
(which is otherwise strictly a user-space matter) as opposed to the
initial environment passed by the kernel (unless modified in-place)?
-hpa
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