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[perl #128255] Assert fail in S_sublex_done without other symptoms

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Dan Collins
May 27, 2016 00:45
[perl #128255] Assert fail in S_sublex_done without other symptoms
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# New Ticket Created by  Dan Collins 
# Please include the string:  [perl #128255]
# in the subject line of all future correspondence about this issue. 
# <URL: >

Greetings Porters,

I have compiled bleadperl with the afl-gcc compiler using:

./Configure -Dusedevel -Dprefix='/usr/local/perl-afl' -Dcc='ccache afl-gcc' -Uuselongdouble -Duse64bitall -Doptimize=-g -Uversiononly -Uman1dir -Uman3dir -Dusequadmath -des
AFL_HARDEN=1 make && make test

And then fuzzed the resulting binary using:

AFL_NO_VAR_CHECK=1 afl-fuzz -i in -o out bin/perl @@

After reducing testcases using `afl-tmin` and performing additional minimization by hand, I have located the following testcase that triggers an assert fail in debug buids of the perl interpreter. The testcase is the file below. On normal builds, this runs normally (albeit with an expected warning). On debug builds, this returns an assert fail.

dcollins@nightshade64:~/perl$ ./perl -Ilib  /usr/local/perl-afl/out/allcrash/f1i000029
Use of comma-less variable list is deprecated at /usr/local/perl-afl/out/allcrash/f1i000029 line 3.
Final $ should be \$ or $name at /usr/local/perl-afl/out/allcrash/f1i000029 line 3, within string
syntax error at /usr/local/perl-afl/out/allcrash/f1i000029 line 3, next char /
Format not terminated at /usr/local/perl-afl/out/allcrash/f1i000029 line 4, at end of line
syntax error at /usr/local/perl-afl/out/allcrash/f1i000029 line 4, at EOF
Execution of /usr/local/perl-afl/out/allcrash/f1i000029 aborted due to compilation errors.

dcollins@nightshade64:~/perl$ cd ../perldebug/
dcollins@nightshade64:~/perldebug$ ./perl -Ilib  /usr/local/perl-afl/out/allcrash/f1i000029
Use of comma-less variable list is deprecated at /usr/local/perl-afl/out/allcrash/f1i000029 line 3.
perl: toke.c:2450: S_sublex_done: Assertion `(PL_parser->lex_inwhat) == OP_SUBST || (PL_parser->lex_inwhat) == OP_TRANS' failed.

dcollins@nightshade64:~/perldebug$ cat /usr/local/perl-afl/out/allcrash/f1i000029
0"$"dcollins@nightshade64:~/perldebug$ od -c /usr/local/perl-afl/out/allcrash/f1i000029
0000000   f   o   r   m   a   t   =  \n   @  \n   0   "   $   "

Debugging tool output is below. A git bisect was performed and reported the following.

5aa91856e21c93226d08f19eb69098f224de5fff is the first bad commit
commit 5aa91856e21c93226d08f19eb69098f224de5fff
Author: Father Chrysostomos <>
Date:   Mon Dec 30 21:18:54 2013 -0800

    toke.c: Remove redundant check

    (and turn it into an assertion.)

    PL_lex_repl can only be set here if we are parsing a substitution
    (OP_SUBST) or transliteration (OP_TRANS).  I believe this check
    has been unnecessary since perl 5.000, which it was added.

:100644 100644 ca306f1455ba8f2c02acd3d7eff3e5490706de84 8ac0f31fb4f85c4ab453b52ec75f92900c448292 M       toke.c
bisect run success


dcollins@nightshade64:~/perldebug$ gdb --args ./miniperl -Ilib /usr/local/perl-afl/out/allcrash/f1i000029
GNU gdb (GDB) 7.10
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
Find the GDB manual and other documentation resources online at:
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./miniperl...done.
(gdb) run
Starting program: /home/dcollins/perldebug/miniperl -Ilib /usr/local/perl-afl/out/allcrash/f1i000029
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/".
Use of comma-less variable list is deprecated at /usr/local/perl-afl/out/allcrash/f1i000029 line 3.
miniperl: toke.c:2450: S_sublex_done: Assertion `(PL_parser->lex_inwhat) == OP_SUBST || (PL_parser->lex_inwhat) == OP_TRANS' failed.

Program received signal SIGABRT, Aborted.
0x00007ffff6cf9478 in raise () from /lib/x86_64-linux-gnu/
(gdb) bt
#0  0x00007ffff6cf9478 in raise () from /lib/x86_64-linux-gnu/
#1  0x00007ffff6cfa8fa in abort () from /lib/x86_64-linux-gnu/
#2  0x00007ffff6cf23a7 in ?? () from /lib/x86_64-linux-gnu/
#3  0x00007ffff6cf2452 in __assert_fail () from /lib/x86_64-linux-gnu/
#4  0x000000000047ea40 in S_sublex_done () at toke.c:2450
#5  0x000000000048b6d5 in Perl_yylex () at toke.c:4728
#6  0x00000000004ba030 in Perl_yyparse (gramtype=258) at perly.c:332
#7  0x00000000004475b4 in S_parse_body (env=0x0, xsinit=0x727694 <xs_init>) at perl.c:2365
#8  0x0000000000446052 in perl_parse (my_perl=0xa7f010, xsinit=0x727694 <xs_init>, argc=3,
    argv=0x7fffffffe5f8, env=0x0) at perl.c:1681
#9  0x00000000007275f3 in main (argc=3, argv=0x7fffffffe5f8, env=0x7fffffffe618)
    at miniperlmain.c:120
(gdb) f 4
#4  0x000000000047ea40 in S_sublex_done () at toke.c:2450
2450            assert (PL_lex_inwhat == OP_SUBST || PL_lex_inwhat == OP_TRANS);
(gdb) l
2445        }
2447        /* Is there a right-hand side to take care of? (s//RHS/ or tr//RHS/) */
2448        assert(PL_lex_inwhat != OP_TRANSR);
2449        if (PL_lex_repl) {
2450            assert (PL_lex_inwhat == OP_SUBST || PL_lex_inwhat == OP_TRANS);
2451            PL_linestr = PL_lex_repl;
2452            PL_lex_inpat = 0;
2453            PL_bufend = PL_bufptr = PL_oldbufptr = PL_oldoldbufptr = PL_linestart = SvPVX(PL_linestr);
2454            PL_bufend += SvCUR(PL_linestr);


No reported memory management errors.

**PERL -V**

dcollins@nightshade64:~/perldebug$ ./perl -Ilib -V
Summary of my perl5 (revision 5 version 25 subversion 2) configuration:
  Commit id: c29dfc6a6c45f86648c51f961304254cc3c449b9
    osname=linux, osvers=4.5.0-2-amd64, archname=x86_64-linux-ld
    uname='linux nightshade64 4.5.0-2-amd64 #1 smp debian 4.5.3-2 (2016-05-08) x86_64 gnulinux '
    config_args='-Dusedevel -Dprefix=/usr/local/perl-afl -Dcc=ccache gcc-6.1 -Duselongdouble -Duse64bitall -Doptimize=-g -Uversiononly -Uman1dir -Uman3dir -DDEBUGGING -DPERL_POISON -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    use64bitint=define, use64bitall=define, uselongdouble=define
    usemymalloc=n, bincompat5005=undef
    cc='ccache gcc-6.1', ccflags ='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion='', gccversion='6.1.0', 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='long double', nvsize=16, Off_t='off_t', lseeksize=8
    alignbytes=16, prototype=define
  Linker and Libraries:
    ld='ccache gcc-6.1', ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/local/lib/gcc/x86_64-pc-linux-gnu/6.1.0/include-fixed /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
    libs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -g -L/usr/local/lib -fstack-protector-strong'

Characteristics of this binary (from libperl):
                        USE_64_BIT_ALL USE_64_BIT_INT USE_LARGE_FILES
                        USE_PERLIO USE_PERL_ATOF
  Built under linux
  Compiled at May 26 2016 17:57:37

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