Perl_pad_fixup_inner_anons: Assertion `SvTYPE(cv) == SVt_PVCV' failed

[dur-randir]

This is a bug report for perl from [email protected],
generated with the help of perlbug 1.41 running under perl 5.31.10.

[Please describe your issue here]

While fuzzing perl v5.31.9-70-g0c96aa4b7b built with afl and run
under libdislocator, I found the following program

for(0){format=
@
my%{format=
@
sub l;
@
my%{format=
@
sub l000l0u0;
@
sub l000l0u0{t f l}

to cause an assertion failure

perl: pad.c:2341: Perl_pad_fixup_inner_anons: Assertion `SvTYPE(cv) == SVt_PVCV' failed.

GDB stack trace is:

#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1 0x00007ffff7c24535 in __GI_abort () at abort.c:79
#2 0x00007ffff7c2440f in __assert_fail_base (fmt=0x7ffff7d86ee0 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
assertion=0x5555559c2ee9 "SvTYPE(cv) == SVt_PVCV", file=0x5555559c2dcb "pad.c", line=2341, function=) at assert.c:92
#3 0x00007ffff7c32102 in __GI___assert_fail (assertion=0x5555559c2ee9 "SvTYPE(cv) == SVt_PVCV", file=0x5555559c2dcb "pad.c", line=2341,
function=0x5555559c4370 <PRETTY_FUNCTION.19244> "Perl_pad_fixup_inner_anons") at assert.c:101
#4 0x000055555567f919 in Perl_pad_fixup_inner_anons (padlist=0x555555c34300, old_cv=0x555555c29dd8, new_cv=0x555555c29d78) at pad.c:2341
#5 0x00005555555c8e60 in Perl_newMYSUB (floor=325, o=0x555555c33f88, proto=0x0, attrs=0x0, block=0x555555c349f0) at op.c:10944
#6 0x0000555555670eaf in Perl_yyparse (gramtype=258) at perly.y:308
#7 0x00005555555f1557 in S_parse_body (env=0x0, xsinit=0x5555555a220f <xs_init>) at perl.c:2579
#8 0x00005555555ef81b in perl_parse (my_perl=0x555555c03260, xsinit=0x5555555a220f <xs_init>, argc=2, argv=0x7fffffffe1b8, env=0x0) at perl.c:1870
#9 0x00005555555a214d in main (argc=2, argv=0x7fffffffe1b8, env=0x7fffffffe1d0) at perlmain.c:132

Bisect points to the following commit, which suggests that the previous fix was not complete:

commit 95c0a76
Author: Father Chrysostomos [email protected]
Date: Sat Sep 10 07:27:43 2016 -0700

pad.c:pad_fixup_inner_anons: Add assertions

These would have made it easier to track down the bug fixed by
the previous commit.

[Please do not change anything below this line]
Flags:
category=core
severity=low
Site configuration information for perl 5.31.10:

Configured by root at Fri Mar 13 17:15:02 MSK 2020.

Summary of my perl5 (revision 5 version 31 subversion 10) configuration:
Commit id: 0c96aa4
Platform:
osname=linux
osvers=4.19.0-8-amd64
archname=x86_64-linux
uname='linux dorothy 4.19.0-8-amd64 #1 smp debian 4.19.98-1 (2020-01-26) x86_64 gnulinux '
config_args='-de -Dusedevel -Doptimize=-O2'
hint=recommended
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='cc'
ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
optimize='-O2'
cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
ccversion=''
gccversion='8.3.0'
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='double'
nvsize=8
Off_t='off_t'
lseeksize=8
alignbytes=8
prototype=define
Linker and Libraries:
ld='cc'
ldflags =' -fstack-protector-strong -L/usr/local/lib'
libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/8/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-2.28.so
so=so
useshrplib=false
libperl=libperl.a
gnulibc_version='2.28'
Dynamic Linking:
dlsrc=dl_dlopen.xs
dlext=so
d_dlsymun=undef
ccdlflags='-Wl,-E'
cccdlflags='-fPIC'
lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'

@inc for perl 5.31.10:
lib
/usr/local/lib/perl5/site_perl/5.31.10/x86_64-linux
/usr/local/lib/perl5/site_perl/5.31.10
/usr/local/lib/perl5/5.31.10/x86_64-linux
/usr/local/lib/perl5/5.31.10

Environment for perl 5.31.10:
HOME=/home/afl
LANG=en_US.UTF-8
LANGUAGE=en_US:en
LC_CTYPE=en_US.UTF-8
LC_TIME=C
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=/home/afl/perlbrew/bin:/home/afl/perlbrew/perls/perl-5.30.0-dbg/bin:/opt/local/bin:/usr/texbin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PERLBREW_HOME=/home/afl/.perlbrew
PERLBREW_MANPATH=/home/afl/perlbrew/perls/perl-5.30.0-dbg/man
PERLBREW_PATH=/home/afl/perlbrew/bin:/home/afl/perlbrew/perls/perl-5.30.0-dbg/bin
PERLBREW_PERL=perl-5.30.0-dbg
PERLBREW_ROOT=/home/afl/perlbrew
PERLBREW_SHELLRC_VERSION=0.88
PERLBREW_VERSION=0.88
PERL_BADLANG (unset)