develooper Front page | perl.perl5.porters | Postings from May 2016

[perl #128261] Assert fail in Perl_sv_2pv_flags: 'subMODIFY_HASH_ATTRIBUTES{}my(%o):s==0'

Thread Previous
From:
Dan Collins
Date:
May 27, 2016 01:57
Subject:
[perl #128261] Assert fail in Perl_sv_2pv_flags: 'subMODIFY_HASH_ATTRIBUTES{}my(%o):s==0'
Message ID:
rt-4.0.18-20190-1464314232-1370.128261-75-0@perl.org
# New Ticket Created by  Dan Collins 
# Please include the string:  [perl #128261]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=128261 >


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:~/perldebug$ ./perl -Ilib -e 'sub MODIFY_HASH_ATTRIBUTES{}my(%o):s==0'
perl: sv.c:2595: Perl_sv_2nv_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


This seems to be the "hash equivalent" of [perl #128183]?


Debugging tool output is below. A git bisect was performed and reported the following, which is the commit where the assert was initially added.

217f6fa330a187be32a68556507e3165b8747f55 is the first bad commit
commit 217f6fa330a187be32a68556507e3165b8747f55
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 32a609747bffb for instance

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



**GDB**

dcollins@nightshade64:~/perldebug$ gdb --args ./perl -Ilib -e 'sub MODIFY_HASH_ATTRIBUTES{}my(%o):s==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 ./perl...done.
(gdb) run
Starting program: /home/dcollins/perldebug/perl -Ilib -e sub\ MODIFY_HASH_ATTRIBUTES\{\}my\(%o\):s==0
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
perl: sv.c:2595: Perl_sv_2nv_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  0x00000000005cd9fc in Perl_sv_2nv_flags (sv=0xab2730, flags=0) at sv.c:2594
#5  0x000000000062c724 in Perl_do_ncmp (left=0xab2730, right=0xab27a8) at pp.c:2281
#6  0x00000000005a933d in Perl_pp_eq () at pp_hot.c:464
#7  0x000000000055a245 in Perl_runops_debug () at dump.c:2239
#8  0x00000000004623d3 in S_run_body (oldscope=1) at perl.c:2517
#9  0x00000000004619fe in perl_run (my_perl=0xa9c010) at perl.c:2440
#10 0x000000000041eae0 in main (argc=4, argv=0x7fffffffe608, env=0x7fffffffe630)
    at perlmain.c:116
(gdb) f 4
#4  0x00000000005cd9fc in Perl_sv_2nv_flags (sv=0xab2730, flags=0) at sv.c:2594
2594        assert (SvTYPE(sv) != SVt_PVAV && SvTYPE(sv) != SVt_PVHV
(gdb) l
2589    NV
2590    Perl_sv_2nv_flags(pTHX_ SV *const sv, const I32 flags)
2591    {
2592        PERL_ARGS_ASSERT_SV_2NV_FLAGS;
2593
2594        assert (SvTYPE(sv) != SVt_PVAV && SvTYPE(sv) != SVt_PVHV
2595             && SvTYPE(sv) != SVt_PVFM);
2596        if (SvGMAGICAL(sv) || SvVALID(sv) || isREGEXP(sv)) {
2597            /* FBMs use the space for SvIVX and SvNVX for other purposes, and use
2598               the same flag bit as SVf_IVisUV, so must not let them cache NVs.
(gdb) info locals
__PRETTY_FUNCTION__ = "Perl_sv_2nv_flags"
(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: c29dfc6a6c45f86648c51f961304254cc3c449b9
  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
    .


Thread Previous


nntp.perl.org: Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at ask@perl.org | Group listing | About