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Bug#186366: marked as done ([libapt-pkg] apt-get segfaults on corrupt /var/cache/apt/*.bin)

Your message dated Fri, 19 Aug 2011 12:05:22 +0200
with message-id <20110819115258.GA4040@debian.org>
and subject line Re: Bug#81829: "Segmentation faulty tree" (#270147) still present in Lenny, broken /var/cache/apt/*.bin available for download
has caused the Debian Bug report #81829,
regarding [libapt-pkg] apt-get segfaults on corrupt /var/cache/apt/*.bin
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
81829: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=81829
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Package: apt
Version: 0.5.4
Severity: important

After a recent dist-upgrade, which succeeded, subsequent apt-get
install/upgrade/dist-upgrade operations fail with a segmentation fault.

cyclops:/var/cache/apt# apt-get dist-upgrade
Reading Package Lists... Done
Building Dependency Tree... Done
Calculating Upgrade... Done
The following NEW packages will be installed:
  python-htmlgen python2.2-htmlgen 
15 packages upgraded, 2 newly installed, 0 to remove and 0  not upgraded.
Need to get 8246kB of archives. After unpacking 319kB will be used.
Do you want to continue? [Y/n] 
Get:1 http://192.168.1.16 sid/main debconf 1.2.34 [139kB]
Segmentation fault (core dumped)

gdb backtrace on the core file shows:

(gdb) bt
#0  0x40083225 in pkgAcquireStatus::Pulse () from /usr/lib/libapt-pkg-libc6.2-3-2.so.3.2
#1  0x08064237 in strcpy ()
#2  0x4008181a in pkgAcquire::Run () from /usr/lib/libapt-pkg-libc6.2-3-2.so.3.2
#3  0x08051b9c in strcpy ()
#4  0x0805a9a1 in strcpy ()
#5  0x4005f31a in CommandLine::DispatchArg () from /usr/lib/libapt-pkg-libc6.2-3-2.so.3.2
#6  0x08063610 in strcpy ()
#7  0x40175a51 in __libc_start_main () from /lib/libc.so.6


strace of the program ends in:

select(14, [13], [], NULL, {0, 500000}) = 1 (in [13], left {0, 500000})
read(13, "102 Status\nURI: http://192.168.1";..., 4000) = 271
select(14, [13], [], NULL, {0, 500000}) = 1 (in [13], left {0, 500000})
read(13, "102 Status\nURI: http://192.168.1";..., 4000) = 118
select(14, [13], [], NULL, {0, 500000}) = 1 (in [13], left {0, 390000})
read(13, "200 URI Start\nURI: http://192.16";..., 4000) = 153
Get:1 http://192.168.1.16 sid/main debconf 1.2.34 [139kB]
) = 72
stat64("/var/cache/apt/archives/partial/debconf_1.2.34_all.deb", {st_mode=S_IFREG|0644, st_size=116176, ...}) = 0
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++

As suggested in other bug reports, I renamed /var/cache/apt/*.bin to
/var/cache/apt/*.bin.bak and reran the above commands and there was no
change.  (It still segfaulted.)


Eric

--- End Message ---
--- Begin Message --- 
Source: apt
Source-Version: 0.8.16~exp4

apt (0.8.16~exp4) experimental; urgency=low

   [ Julian Andres Klode ]
   * apt-pkg/pkgcache.h:
     - [ABI break] Add pkgCache::Header::CacheFileSize, storing the cache size
   * apt-pkg/pkgcachegen.cc:
     - Write the file size to the cache
   * apt-pkg/pkgcache.cc:
     - Check that cache is at least CacheFileSize bytes large (LP: #16467)

On Thu, Aug 18, 2011 at 04:16:05PM -0500, Jonathan Nieder wrote:
> tags 81829 - moreinfo
> quit
> 
> Axel Beckert wrote:
> 
> > I occasionally ran into this bug on Lenny, can't remember on which
> > platform, but never deterministically.
> >
> > But today I reproducibly ran into this bug with both, apt-get and
> > aptitude. Independent of what I did: aptitude; aptitude -u; aptitude
> > upgrade; apt-get upgrade, I always get the "Segmentation faulty
> > tree... 50%" ("Building dependency tree... 50%^MSegmentation fault").
> >
> > Moving /var/lib/apt/extended_states away didn't help.
> >
> > Couldn't even do an apt-get install gdb for generating a backtrace.
> >
> > Moving away pkgcache.bin and srcpkgcache.bin from /var/cache/apt/
> > finally did help (thanks to waldi for that hint), but copying them
> > back after upgrading two packages didn't reproduce the segfault --
> > they always got recreated.
> 
> Thanks!  No promises about being able to take a look soon, but I've
> downloaded them.
I closed the Launchpad bug in 0.8.16~exp4, but forgot to close that 
one. We still cannot detect invalid caches where data changes, but we
can now detect all truncated caches, and reject them.

I could have included a CRC checksum in the header of the remaining
cache, but our experience so far is that 

 (a) most (all?) of these bugs are the result of truncated cache files
 (b) checksumming the cache on opening is much slower than we want,
     especially on ARM systems (200 ms on abel.d.o, 500 ms on an N900,
     12 ms on my Intel Core i5)

That said, if future shows us cases where there are problems with
correctly-sized caches, we can still add a checksum when we break
ABI again, and enable it by default only on amd64 and other fast
architectures.

-- 
Julian Andres Klode  - Debian Developer, Ubuntu Member

See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/.

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