linux-kernel - "core dump helper" runs always as root

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080603182040.GB20582@silmor.de>
Date:	Tue, 3 Jun 2008 20:20:40 +0200
From:	Christian Perle <chris@...uxinfotag.de>
To:	linux-kernel@...r.kernel.org
Subject: "core dump helper" runs always as root

Hi *

I recently played around with the /proc/sys/kernel/core_pattern file
(2.6.24.7 and 2.6.25) and found out that processes started by the
"|/path/to/executable" notation always run as root, even if the
segfaulting process runs as non-root.

Is there a reason for this behaviour? If not, i would suggest starting the
process which receives the core dump on stdin as the same UID of the
segfaulting process.

With the current behaviour you can do funny things:

(as root)
# echo "|/bin/chmod 4755 /bin/ash" > /proc/sys/kernel/core_pattern

(as user)
$ sleep 2 & kill -11 $!

Of course this is *not* a local root exploit because you need to be root
to write to the proc entry, but IMHO running the "core dump helper" (is
there a better name for this?) always as root is potentially harmful.

Greetings,
  Chris
-- 
Christian Perle                                    chris AT linuxinfotag.de
010111                                              http://chris.silmor.de/
101010                          LinuxGuitarKitesBicyclesBeerPizzaRaytracing
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/