# New Ticket Created by Dan Collins
# Please include the string: [perl #128258]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/Ticket/Display.html?id=128258 >

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 a segfault in the perl interpreter. The testcase is the file below. On normal builds and debug builds, this segfaults.

dcollins@nightshade64:~/perl$ ./miniperl -Ilib -e 'sub UNIVERSAL::DESTROY{$e=bless[]}'
Segmentation fault

This is a stack overflow issue due to infinite recursion. Here is the looping series of stack frames:

#943 0x000000000053c07b in Perl_free_tmps () at scope.c:207
#944 0x000000000043017d in Perl_call_sv (sv=0x8539a0, flags=45) at perl.c:2887
#945 0x000000000050dba4 in S_curse (sv=0x19b8550, check_refcnt=true) at sv.c:6853
#946 0x000000000050c574 in Perl_sv_clear (orig_sv=0x19b8598) at sv.c:6457
#947 0x000000000050df22 in Perl_sv_free2 (sv=0x19b8598, rc=1) at sv.c:6954
#948 0x000000000053b8aa in S_SvREFCNT_dec_NN (sv=0x19b8598) at inline.h:177

Valgrind concurs:

==7488== Stack overflow in thread #1: can't grow stack to 0xffe801000
==7488== Process terminating with default action of signal 11 (SIGSEGV)
==7488== Access not within mapped region at address 0xFFE801F6C
==7488== Stack overflow in thread #1: can't grow stack to 0xffe801000
==7488== at 0x53DA15: Perl_leave_scope (scope.c:801)
==7488== If you believe this happened as a result of a stack
==7488== overflow in your program's main thread (unlikely but
==7488== possible), you can try to increase the size of the
==7488== main thread stack using the --main-stacksize= flag.
==7488== The main thread stack size used in this run was 8388608.
==7488== Stack overflow in thread #1: can't grow stack to 0xffe801000

A bisect was attempted but this behavior has persisted since 5.12.0 at least.

**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
     libc=libc-2.22.so, 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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postedMay 27, '16 at 1:33a
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