Bug#792088: apt-get install segfaults with certain repository configurations

[Rich <rercola@acm.jhu.edu>]

As a bonus, here's a partial stacktrace, with apt rebuilt with nostrip:

#0  0x00007f75d1e05b10 in vtable for pkgDepCache () from
/usr/lib/x86_64-linux-gnu/libapt-pkg.so.4.12
#1  0x00007f75d205fda9 in pkgCache::Iterator<pkgCache::Package,
pkgCache::PkgIterator>::end (this=0x7fff16a97660) at
../build/include/apt-pkg/cacheiterators.h:64
#2  0x00007f75d1b33749 in pkgDepCache::IsModeChangeOk
(this=0x7f75d39c04a0, mode=pkgDepCache::ModeKeep, Pkg=..., Depth=0,
FromUser=false) at /root/apt-1.0.9.10/apt-pkg/depcache.cc:918
#3  0x00007f75d1b32e6e in pkgDepCache::MarkKeep (this=0x7f75d39c04a0,
Pkg=..., Soft=false, FromUser=false, Depth=0) at
/root/apt-1.0.9.10/apt-pkg/depcache.cc:769
#4  0x00007f75d1b2d5e4 in pkgProblemResolver::ResolveInternal
(this=0x7f75d3a6d5a0, BrokenFix=true) at
/root/apt-1.0.9.10/apt-pkg/algorithms.cc:1061
#5  0x00007f75cefbf258 in ?? ()
#6  0x00007f75d39c0ce0 in ?? ()
#7  0x0000000000000000 in ?? ()

valgrind helpfully reports:
==1801== Use of uninitialised value of size 8
==1801==    at 0x131D9D: pkgCache::Iterator<pkgCache::Package,
pkgCache::PkgIterator>::end() const (in /usr/bin/apt-get)
==1801==    by 0x4F90748:
pkgDepCache::IsModeChangeOk(pkgDepCache::ModeList,
pkgCache::PkgIterator const&, unsigned long, bool) (depcache.cc:918)
==1801==    by 0x4F8FE6D: pkgDepCache::MarkKeep(pkgCache::PkgIterator
const&, bool, bool, unsigned long) (depcache.cc:769)
==1801==    by 0x4F8A5E3: pkgProblemResolver::ResolveInternal(bool)
(algorithms.cc:1061)
==1801==    by 0x7BF2257: ??? (in /var/cache/apt/pkgcache.bin)
==1801==
==1801==
==1801== Process terminating with default action of signal 11
(SIGSEGV): dumping core
==1801==  Bad permissions for mapped region at address 0x5262B10
==1801==    at 0x5262B10: vtable for pkgDepCache (in
/usr/lib/x86_64-linux-gnu/libapt-pkg.so.4.12.0)
==1801==    by 0x4F90748:
pkgDepCache::IsModeChangeOk(pkgDepCache::ModeList,
pkgCache::PkgIterator const&, unsigned long, bool) (depcache.cc:918)
==1801==    by 0x4F8FE6D: pkgDepCache::MarkKeep(pkgCache::PkgIterator
const&, bool, bool, unsigned long) (depcache.cc:769)
==1801==    by 0x4F8A5E3: pkgProblemResolver::ResolveInternal(bool)
(algorithms.cc:1061)
==1801==    by 0x7BF2257: ??? (in /var/cache/apt/pkgcache.bin)



- Rich