Segfault in Perl_ck_shift (op.c:12664)

[p5pRT]

Migrated from rt.perl.org#134012 (status was 'new')

Searchable as RT134012$

[p5pRT]

From @dur-randir

Created by @dur-randir

While fuzzing perl v5.29.9-63-g2496d8f3f7 built with afl and run
under libdislocator, I found the following program

s,,$0[sub{m]]]],}>0,shift

to segfault. GDB stack trace is following

#0 0x00005555555d8062 in Perl_ck_shift (o=0x555555b77440) at op.c​:12664
#1 0x00005555555b6c74 in Perl_newOP (type=165, flags=0) at op.c​:6174
#2 0x000055555566fc44 in Perl_yyparse (gramtype=258) at perly.y​:1192
#3 0x00005555555ec726 in S_parse_body (env=0x0, xsinit=0x5555555a11f8
<xs_init>) at perl.c​:2531
#4 0x00005555555ea9f8 in perl_parse (my_perl=0x555555b4c260,
xsinit=0x5555555a11f8 <xs_init>, argc=2, argv=0x7fffffffe1c8, env=0x0)
at perl.c​:1822
#5 0x00005555555a113b in main (argc=2, argv=0x7fffffffe1c8,
env=0x7fffffffe1e0) at perlmain.c​:126

This is present a regression between 5.16 and 5.18, bisect points to

commit 9ffcdca
Author​: Father Chrysostomos <sprout@​cpan.org>
Date​: Mon Nov 12 23​:04​:16 2012 -0800

  Don’t leak subs containing syntax errors

  I fixed this for BEGIN blocks earlier, but missed the fact that
  all subs are affected.

Perl Info

Flags:
    category=core
    severity=low

Site configuration information for perl 5.29.9:

Configured by dur-randir at Wed Feb 27 14:51:01 MSK 2019.

Summary of my perl5 (revision 5 version 29 subversion 9) configuration:
  Commit id: c1e47bad34ce1d9c84ed57c9b8978bcbd5a02e98
  Platform:
    osname=darwin
    osvers=13.4.0
    archname=darwin-thread-multi-2level
    uname='darwin isengard.local 13.4.0 darwin kernel version 13.4.0:
mon jan 11 18:17:34 pst 2016; root:xnu-2422.115.15~1release_x86_64
x86_64 '
    config_args='-de -Dusedevel -DDEBUGGING -Dusethreads'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='cc'
    ccflags ='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.9
-DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -DPERL_USE_SAFE_PUTENV'
    optimize='-O3 -g'
    cppflags='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.9
-DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include'
    ccversion=''
    gccversion='4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.56)'
    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='cc'
    ldflags =' -mmacosx-version-min=10.9 -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/6.0/lib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib
/usr/lib
    libs=-lpthread -lgdbm -ldbm -ldl -lm -lutil -lc
    perllibs=-lpthread -ldl -lm -lutil -lc
    libc=
    so=dylib
    useshrplib=false
    libperl=libperl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=bundle
    d_dlsymun=undef
    ccdlflags=' '
    cccdlflags=' '
    lddlflags=' -mmacosx-version-min=10.9 -bundle -undefined
dynamic_lookup -L/usr/local/lib -fstack-protector'



@INC for perl 5.29.9:
    lib
    /usr/local/lib/perl5/site_perl/5.29.9/darwin-thread-multi-2level
    /usr/local/lib/perl5/site_perl/5.29.9
    /usr/local/lib/perl5/5.29.9/darwin-thread-multi-2level
    /usr/local/lib/perl5/5.29.9


Environment for perl 5.29.9:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/dur-randir
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/Users/dur-randir/perlbrew/bin:/Users/dur-randir/perlbrew/perls/perl-5.22.1/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/texbin
    PERLBREW_HOME=/Users/dur-randir/.perlbrew
    PERLBREW_MANPATH=/Users/dur-randir/perlbrew/perls/perl-5.22.1/man
    PERLBREW_PATH=/Users/dur-randir/perlbrew/bin:/Users/dur-randir/perlbrew/perls/perl-5.22.1/bin
    PERLBREW_PERL=perl-5.22.1
    PERLBREW_ROOT=/Users/dur-randir/perlbrew
    PERLBREW_SHELLRC_VERSION=0.84
    PERLBREW_VERSION=0.84
    PERL_BADLANG (unset)
    SHELL=/usr/local/bin/zsh

[demerphq]

This is fixed by PR #20168

[zb226]

This issue

$ cat ../gh16944-reproducer.pl
s,,$0[sub{m]]]],}>0,shift

does not crash in blead and bisecting with

Porting/bisect.pl --start=v5.37.0 --end=v5.38.0 -DDEBUGGING --target=miniperl -- \
    bash -c './miniperl ../gh16944-reproducer.pl; [ $? -eq 139 ] && exit 0 || exit 1'

points to eb54d46 for the fix, which is PR #20168 by @demerphq.

Verifying with a full perl build:

$ git describe
v5.37.3-255-g14580ae6b9
$ ./perl ../gh16944-reproducer.pl
Segmentation fault (core dumped)

(...)

$ git describe
v5.37.3-256-geb54d46f72
$ ./perl ../gh16944-reproducer.pl
syntax error at ../gh16944-reproducer.pl line 1, near "m]]]"
Execution of ../gh16944-reproducer.pl aborted due to compilation errors.

Consequently, I think this issue can be closed.