Re: [Pan-users] Re: Pan v0.14.2.91 crashing X hard (black screen)/messing up NVIDIA card badly...

[Phillip Pi]

FYI. I ran strace and pan --debug separately in case they help you, Pan 
developers. 
http://alpha.zimage.com/~ant/temp/Pan-straceANDdebug.zip (will be deleted 
eventually)..


On Sat, Aug 26, 2006 at 12:04:49PM -0700, Phillip Pi wrote:
> > > NVIDIA poster told me to collect logs in my NVIDIA forum thread. I 
> > > gathered the newsgroup thread 
> > > datas:
> > > 
> > > The newsgroup threads (not even reading a thread -- just the list)
> > > that crashes are (copied and pasted):
> > > Subject:
> > > =?ISO-8859-1?Q?Cablebox_->DVD._Later_DVD->MP4_using_Handbrake_Mpeg-4_Video_/_AAC_Audio_,_FFMEG,_400kpbs_AVB,_2-pass_encoding,_22050_Sample_Rate,_128kbps_Bitrate.=0D=0DParts_3_and_4.=0D=0Dhttp://www.hbo.com/docs/programs/whentheleveesbroke/index.html=0D=0D=0D=0DThis_intimate,_heart-rending_portrait_of_New_Orleans_in_the_wake_of_the_destruction_tells_the_heartbreaking_personal_stories_of_those_who_endured_this_harrowing_ordeal_and_survived_to_tell_the_tale_of_misery,_despair_and_triumph._=0D=0DThe_film_also_looks_at_a_community_that_has_been_through_hell_and_back,_surviving_death,_devastation_and_disease_at_every_turn._Yet,_somehow,_amidst_the_ruins,_the_people_of_New_Orleans_are_finding_new_hope_and_strength_as_the_city_rises_from_the_ashes,_buoyed_by_their_own_resilience_and_a_rich_cultural_legacy._=0D=0D"New_Orleans_is_fighting_for_its_life,"_says_Lee._"These_are_not_people_who_will_disappear_quietly_-_they're_accustomed_to_hardship_and_slights,_and_they'll_fight_for_New_O
> >  rleans._This_film_will_showcase_the
> > > From: spike
> > > Newsgroups:   alt.binaries.ipod.videos.movies
> > > Date:         Thu, 24 Aug 2006 08:02:33 -0700
> > > 
> > > I think that ISO thing is making it my whole X server crash hard. Is Pan
> > > supposed to read this correctly?
> > 
> > It could be (making it crash).  Old-pan did handle strange encodings, but
> > had a few bugs (or at least one, but irritating as it could cause crashes)
> > in the way it did it. That's the worst known crashing issue it had (altho
> > the scaling issues were well known and are dealt with in new-pan, but
> > those didn't cause crashes).
> > 
> > I've suspected that was what it was, but wanted to verify or at least
> > narrow it down before I made that claim.  That is in fact one of the
> > reasons I have been pushing new-pan hard, lately, is because AFAIK it
> > doesn't have the problem, at least with crashing, that old-pan did on
> > strange language headers.  (New-pan doesn't always interpret them,
> > sometimes leaving them as iso-whatever in the subject or from column, tho
> > it seems to do OK on the body with appropriate language headers, but I've
> > not seen it crash.)
> > 
> > The thing about crashes (in general, not pan specifically), particularly in
> > C and C++ programs, is that crashes fairly often mark possible exploits,
> > at least on x86 with its lack of solid memory protection, as many of those
> > crashes are reading past the end of a buffer or other such memory errors. 
> > If an attacker can initialize that memory with malware instructions, it's
> > often possible to get the program to execute them instead of crashing. 
> > While the malware would execute with the permissions of the person running
> > the program (unless it's SUID/SGID), not as root (unless you are running
> > it as root), that's bad enough.
> > 
> > Luckily, user targeted applications on Linux aren't commonly malware
> > targeted yet, with the possible semi-exception of browsers, so it's not a
> > huge problem, but it's a serious problem none-the-less.  I do /not/ like
> > crashes in my internet enabled programs, particularly when they are
> > dealing with untrusted internet served data!
> > 
> > In addition, the weird data causing the crashes in pan is just the sort of
> > thing that would be expected to cause exactly this type of major security
> > issue buffer overruns -- unexpected 8-bit or even multi-byte data in a
> > place where 7-bit ascii data is likely to be assumed.  This crash has
> > therefore bothered me every since I realized what was apparently causing
> > it, and I've been rather glad new-pan seems more stable in that regard.
> > 
> > Now, it should also be said that there are ways to "crash safely", and
> > that pan and the libraries it uses may very well be coded to do so.  I'm
> > not a C/C++/assembly coder nor do I know all that much about "hardening" a
> > system using memory buffer canaries (tho I do know the general technique
> > is to put a pattern in the memory immediately after such a buffer, and
> > after use of the buffer, check that pattern to see if it's changed, the
> > safety zone and the pattern in it then being the canary) or the like, to be
> > able to read pan's code (and that of its libraries) and know if this is a
> > real security vuln or not. However, there's certainly a possibility that
> > it is, as there is with any such crashes, particularly on unexpected data.
> > 
> > Anyway, um... are you sure you want to keep running it now?
> 
> I did find a workaround. Don't read those specific threads. I made a backup 
> copy of that so I 
> can reproduce it again if needed to.
> 
> What I don't understand is why Gnome was able to handle it without crashing. 
> I did notice a 1 
> second pause until garbled came up. KDE, ouch.
> 
> 
> > Of course, one thing you could do is create a new user and group, set the
> > pan executable to that user and group and SUID/SGID, and make that group
> > relatively unprivileged so it can't read any of the private stuff on your
> > system and /certainly/ can't overwrite anything but its own stuff.  That's
> > the general technique used for various system daemons and the like,
> > particularly internet exposed ones.  You could even run it in a chroot if
> > you are that concerned about the crashes.
> > 
> > Anyway... I went ahead and got the newshosting account and am busy
> > setting it up and catching up on stuff now.  Anybody that might have
> > wished to sponsor me and get a bit of free money off of newshosting, too
> > late now! =8^P  I haven't gotten to that group yet, but I get tonite (Sat)
> > off work for the first time in awhile, and unless they call me in, that's
> > when I'm planning to check on that group.  I still have old-pan installed
> > too, so can see how it behaves in both versions.
-- 
"Ever watch ants just crawling around? They walk in that single straight line, 
a long, a long, long mile of ants. Sometimes they will walk over and pick up 
their dead friends and carry those around. I'm pretty sure it's because they 
can get in the carpool lane and pass up that line." --Ellen DeGeneres
  /\___/\
 / /\ /\ \     Phillip (Ant) @ http://antfarm.ma.cx (Personal Web Site)
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