From @dcollinsn

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 -e '(vec%0,0,0)=0'
Illegal number of bits in vec at -e line 1.
dcollins@nightshade64:~/perl$ cd ../perldebug/
dcollins@nightshade64:~/perldebug$ ./perl -Ilib -e '(vec%0,0,0)=0'
perl: sv.c:2924: Perl_sv_2pv_flags: Assertion `((svtype)((sv)->sv_flags & 0xff)) != SVt_PVAV && ((svtype)((sv)->sv_flags & 0xff)) != SVt_PVHV && ((svtype)((sv)->sv_flags & 0xff)) != SVt_PVFM' failed.
Aborted

Debugging tool output is below. A git bisect was performed and reported the following, which appears to be when the assert was initially added.

217f6fa is the first bad commit
commit 217f6fa
Author: Father Chrysostomos <sprout@cpan.org>
Date: Fri Jul 19 08:51:47 2013 -0700

sv.c: Assert that sv_[ivp]v are not passed aggregates

The lack of assertions can hide bugs. See 32a6097 for instance

:100644 100644 3ac0a2bce83bc12406be1fa22acefa8f8a2014c7 daa87f00081d96c8d15f94f02c32cd85e8af0266 M sv.c
bisect run success

**GDB**

dcollins@nightshade64:~/perldebug$ gdb --args ./miniperl -Ilib -e '((vec%0,0,0)=0)'
GNU gdb (GDB) 7.10
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
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 -e $\(vec%0,0,0$=0\)
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
miniperl: sv.c:2924: Perl_sv_2pv_flags: Assertion `((svtype)((sv)->sv_flags & 0xff)) != SVt_PVAV && ((svtype)((sv)->sv_flags & 0xff)) != SVt_PVHV && ((svtype)((sv)->sv_flags & 0xff)) != SVt_PVFM' failed.

Program received signal SIGABRT, Aborted.
0x00007ffff6cf9478 in raise () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0 0x00007ffff6cf9478 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007ffff6cfa8fa in abort () from /lib/x86_64-linux-gnu/libc.so.6
#2 0x00007ffff6cf23a7 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#3 0x00007ffff6cf2452 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6
#4 0x00000000005b551c in Perl_sv_2pv_flags (sv=0xa959a8, lp=0x7fffffffe1e8, flags=2050)
at sv.c:2923
#5 0x0000000000694542 in Perl_do_vecget (sv=0xa959a8, offset=0, size=0) at doop.c:752
#6 0x000000000061d3ab in Perl_pp_vec () at pp.c:3509
#7 0x000000000053fac1 in Perl_runops_debug () at dump.c:2239
#8 0x00000000004482ec in S_run_body (oldscope=1) at perl.c:2517
#9 0x0000000000447917 in perl_run (my_perl=0xa7f010) at perl.c:2440
#10 0x000000000072760b in main (argc=4, argv=0x7fffffffe618, env=0x7fffffffe640)
at miniperlmain.c:122
(gdb) q

**VALGRIND**

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: c29dfc6
Platform:
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
Compiler:
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',
optimize='-g',
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
libc=libc-2.22.so, so=so, useshrplib=false, libperl=libperl.a
gnulibc_version='2.22'
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):
Compile-time options: DEBUGGING HAS_TIMES PERLIO_LAYERS PERL_COPY_ON_WRITE
PERL_DONT_CREATE_GVSV
PERL_HASH_FUNC_ONE_AT_A_TIME_HARD PERL_MALLOC_WRAP
PERL_OP_PARENT PERL_PRESERVE_IVUV PERL_USE_DEVEL
USE_64_BIT_ALL USE_64_BIT_INT USE_LARGE_FILES
USE_LOCALE USE_LOCALE_COLLATE USE_LOCALE_CTYPE
USE_LOCALE_NUMERIC USE_LOCALE_TIME USE_LONG_DOUBLE
USE_PERLIO USE_PERL_ATOF
Built under linux
Compiled at May 26 2016 17:57:37
@INC:
lib
/usr/local/perl-afl/lib/site_perl/5.25.2/x86_64-linux-ld
/usr/local/perl-afl/lib/site_perl/5.25.2
/usr/local/perl-afl/lib/5.25.2/x86_64-linux-ld
/usr/local/perl-afl/lib/5.25.2
/usr/local/perl-afl/lib/site_perl/5.25.1
/usr/local/perl-afl/lib/site_perl/5.24.0
/usr/local/perl-afl/lib/site_perl
.

Assert fail in Perl_sv_2pv_flags: '(vec%0,0,0)=0' #15370

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