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Segfault in Perl_cv_undef_flags #16032

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p5pRT opened this issue Jun 22, 2017 · 3 comments
Open

Segfault in Perl_cv_undef_flags #16032

p5pRT opened this issue Jun 22, 2017 · 3 comments

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@p5pRT
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p5pRT commented Jun 22, 2017

Migrated from rt.perl.org#131631 (status was 'open')

Searchable as RT131631$

@p5pRT
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p5pRT commented Jun 22, 2017

From @dur-randir

Created by @dur-randir

While fuzzing perl v5.27.1-37-g4c95ee9f29 built with afl and run
under libdislocator, I found the following program

m|$0[sub{$0[o{warn]]]]|}}

to crash, even when run under -c for a syntax check. GDB info about
the crash location is​:

#0 0x0000564b247bd269 in Perl_cv_undef_flags (cv=0x564b257f8340,
flags=0x0) at pad.c​:398
398 U32 inner_rc = SvREFCNT(innercv);
gdb$ bt
#0 0x0000564b247bd269 in Perl_cv_undef_flags (cv=0x564b257f8340,
flags=0x0) at pad.c​:398
#1 0x0000564b247bc819 in Perl_cv_undef (cv=0x564b257f8340) at pad.c​:289
#2 0x0000564b248e71ed in Perl_sv_clear (orig_sv=0x564b257f8340) at sv.c​:6631
#3 0x0000564b248ea37e in Perl_sv_free2 (sv=0x564b257f8340, rc=0x1) at sv.c​:7081
#4 0x0000564b24731e4a in S_SvREFCNT_dec (sv=0x564b257f8340) at inline.h​:189
#5 0x0000564b2473301a in perl_destruct (my_perl=0x564b257f6010) at perl.c​:867
#6 0x0000564b246effc7 in main (argc=0x2, argv=0x7ffd34abc078,
env=0x7ffd34abc090) at perlmain.c​:134
gdb$ p innercv
$1 = (CV * const) 0x0

Perl Info

Flags:
    category=core
    severity=medium

Site configuration information for perl 5.27.1:

Configured by root at Sun May 28 01:44:41 MSK 2017.

Summary of my perl5 (revision 5 version 26 subversion 0) configuration:
  Derived from: 4c95ee9f298c2edfc1382d540ff89288790e78b6
  Platform:
    osname=linux
    osvers=4.9.0-3-amd64
    archname=x86_64-linux
    uname='linux dorothy 4.9.0-3-amd64 #1 smp debian 4.9.25-1
(2017-05-02) x86_64 gnulinux '
    config_args='-des -Dusedevel -DDEBUGGING -Dcc=afl-clang-fast
-Doptimize=-O0 -g -ggdb3 -fno-omit-frame-pointer'
    hint=previous
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='afl-clang-fast'
    ccflags ='-DDEBUGGING -fno-strict-aliasing -pipe
-fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O0 -g -ggdb3 -fno-omit-frame-pointer'
    cppflags='-DDEBUGGING -fno-strict-aliasing -pipe
-fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='4.2.1 Compatible Clang 3.9.1 (tags/RELEASE_391/rc2)'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='afl-clang-fast'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/lib
/usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu
/lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
/usr/local/lib /usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/lib
/usr/include/x86_64-linux-gnu /usr/lib
    libs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.24.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.24'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O0 -g -ggdb3 -fno-omit-frame-pointer
-L/usr/local/lib -fstack-protector-strong'

Locally applied patches:
    uncommitted-changes


@INC for perl 5.27.1:
    lib
    /usr/local/lib/perl5/site_perl/5.26.0/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.26.0
    /usr/local/lib/perl5/5.26.0/x86_64-linux
    /usr/local/lib/perl5/5.26.0


Environment for perl 5.27.1:
    HOME=/home/afl
    LANG=en_US.UTF-8
    LANGUAGE=en_US:en
    LC_CTYPE=en_US.UTF-8
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/afl/perlbrew/bin:/home/afl/perlbrew/perls/perl-5.24.1-dbg/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
    PERLBREW_BASHRC_VERSION=0.78
    PERLBREW_HOME=/home/afl/.perlbrew
    PERLBREW_MANPATH=/home/afl/perlbrew/perls/perl-5.24.1-dbg/man
    PERLBREW_PATH=/home/afl/perlbrew/bin:/home/afl/perlbrew/perls/perl-5.24.1-dbg/bin
    PERLBREW_PERL=perl-5.24.1-dbg
    PERLBREW_ROOT=/home/afl/perlbrew
    PERLBREW_VERSION=0.78
    PERL_BADLANG (unset)
    SHELL=/usr/bin/zsh

@p5pRT
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p5pRT commented Dec 30, 2017

From zefram@fysh.org

This is yet another bug based on parser error recovery screwing up stack
synchronisation. I've converted the segv into an assertion failure in
commit dce3f5c, but the actual bug with
error recovery remains.

-zefram

@p5pRT
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p5pRT commented Dec 30, 2017

The RT System itself - Status changed from 'new' to 'open'

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