[Bug libc/12489] New: prelinking ldso causes binaries to segfault upon startup

["vapier at gentoo dot org" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=12489

           Summary: prelinking ldso causes binaries to segfault upon
                    startup
           Product: glibc
           Version: 2.13
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: vapier@gentoo.org
                CC: schwab@linux-m68k.org, toolchain@gentoo.org,
                    allan@archlinux.org


after upgrading from glibc-2.12.2 to glibc-2.13 and running prelink on the
system, many binaries segfault immediately.  undoing prelink on just the ldso
makes the segfaults go away.

using git bisect from the glibc-2.12 tag to the glibc-2.13 tag shows the
trouble starts around commit bc5fb0374c3ce6eca92f44d13a55b066e707c4a0 (Don't
try to free rpath strings allocated during startup).  and indeed, if i take
current master (edf9294e7a2cd46b050faf2d270d28ff477f6c5e) and revert that one
commit, things still work fine.  same goes for taking glibc-2.13 and reverting
that one change.

http://sourceware.org/git/?p=glibc.git;a=commit;h=bc5fb0374c3ce6eca92f44d13a55b066e707c4a0

full bisect log:
# bad: [6392473fe970b0cdace62f31000a83ba0fcf6161] 2.13 release
# good: [e28c88707ef0529593fccedf1a94c3fce3df0ef3] Prepare for release. git
bisect start 'glibc-2.13' 'glibc-2.12'
# good: [c96d23fcaa7072bb9e7669957c90b09dddfd9161] Fixup x86 after x86-64
varshift change.
git bisect good c96d23fcaa7072bb9e7669957c90b09dddfd9161
# good: [c96d23fcaa7072bb9e7669957c90b09dddfd9161] Fixup x86 after x86-64
varshift change.
git bisect good c96d23fcaa7072bb9e7669957c90b09dddfd9161
# bad: [fdc0f374bcd2d0513569aa8d600f960e43e8af1d] Fix perturbing in malloc on
free.
git bisect bad fdc0f374bcd2d0513569aa8d600f960e43e8af1d
# bad: [91c42559190f59c6c4b3cb0b7f5c9bb11dd28161] powerpc: Use generic memset
for RTLD for ppc32/64
git bisect bad 91c42559190f59c6c4b3cb0b7f5c9bb11dd28161
# good: [e66e7419a6f58200eec6941b14e2dcff9875cc6c] Actually make it possible to
user the default name server.
git bisect good e66e7419a6f58200eec6941b14e2dcff9875cc6c
# bad: [dda51327baa01c8e5c188a9952317396bb5569b1] Undo feature selection for
ftruncate.
git bisect bad dda51327baa01c8e5c188a9952317396bb5569b1
# bad: [8ffcee4a049b244e369e371536486a9b2eabb25f] Fix limit detection in x86-64
SSE2 strncasecmp.
git bisect bad 8ffcee4a049b244e369e371536486a9b2eabb25f
# bad: [7291c56f9d6f5861d1c001bc63a364f047a74738] Fix register conflict in s390
____longjmp_chk
git bisect bad 7291c56f9d6f5861d1c001bc63a364f047a74738
# bad: [bc5fb0374c3ce6eca92f44d13a55b066e707c4a0] Don't try to free rpath
strings allocated during startup
git bisect bad bc5fb0374c3ce6eca92f44d13a55b066e707c4a0

the simple test script i was using (probably should automate this with `git
bisect run`, but oh well):
rm -rf chroot
mkdir chroot
cd chroot
mkdir lib etc bin
ln -s lib lib64
cp `which gcc` `which prelink` bin
cp /etc/prelink.conf etc
cp ../lib*.so.? lib/
cp ../elf/ld.so lib/ld-linux-x86-64.so.2
sudo chroot . prelink -a
sudo chroot . gcc

if gcc crashes, then it doesnt look so good

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