[Bug 7763] ppp: out-of-memory 30min after "LCP terminated by peer"

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------- Additional Comments From debzilla at ubuntu.com  2005-03-20 15:00 UTC -------
Message-ID: <423D8914.4040705 at g-house.de>
Date: Sun, 20 Mar 2005 15:30:44 +0100
From: Christian Kujau <evil at g-house.de>
To: 299875 at bugs.debian.org
CC: Marco d'Itri <md at Linux.IT>, 
 Justin Pryzby <justinpryzby at users.sourceforge.net>
Subject: Re: Bug#299875: ppp: out-of-memory 30min after "LCP terminated by
 peer"

hi again,

sorry for the delay, but the "bug" triggers only when the remote peer
disconnects me - and it does it only once a day.

Marco d'Itri wrote:
> reassign 299875 kernel
> retitle 299875 CAN-2005-0384: Remote Linux DoS on ppp servers
> tag 299875 patch security

yes, it really looks like a "pppd DoS", but as i suspected, things are a
bit different here:

- pppoe receives PADT from peer
- pppd in turn gets "LCP terminated by peer"
- pppd tries to re-establish the connection, says "Starting link" in the
  logfile [1] and then just hangs.

i have to re-adjust the subject line, because OOM was triggered by
something else, *because* pppd did not succeed to re-establish the
connection. but oom is totally unrelated here (and fixed on my system).

but still: pppd hangs and is only killable via "kill -9". but it is *NOT*
a cpu hog as stated by Paul Mackerras.

i've strace'd the hanging pppd:

http://nerdbynature.de/bits/sheep/2.6.11/oom/pppd_2.6.11.4.log

(the very first line is the only one i get from just doing
 "strace -p `pidof pppd`", then i did "killall pppd, then with -9)

to summarise: i've noticed the pppd behaviour first with 2.6.11, then with
2.6.11-rc5-bk2, now with 2.6.11.3 and 2.6.11.4. downgrading to
ppp_2.4.2+20040428-6_i386 "solves" it.

thank you for your time,
Christian.

PS: i'll close the issue i reported on lkml:
http://www.ussg.iu.edu/hypermail/linux/kernel/0503.2/0316.html

[1] http://nerdbynature.de/bits/sheep/2.6.11/oom/oom_2.6.11.3.txt
-- 
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UBNC (user brain not connected)




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