Assertion failure in Perl_sv_vcatpvfn_flags (sv.c:12497)

[p5pRT]

Migrated from rt.perl.org#134013 (status was 'new')

Searchable as RT134013$

[p5pRT]

From @dur-randir

Created by @dur-randir

While fuzzing perl v5.29.9-63-g2496d8f3f7 built with afl and run
under libdislocator, I found the following program

eval q!format=
@​
for(0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
!

to cause an assertion failure

perl​: sv.c​:12497​: void Perl_sv_vcatpvfn_flags(SV *const, const char
*const, const STRLEN, va_list *const, SV **const, const size_t, _Bool
*const, const U32)​: Assertion `0' failed.

GDB stack trace is following

#0 __GI_raise (sig=sig@​entry=6) at ../sysdeps/unix/sysv/linux/raise.c​:50
#1 0x00007ffff7c25535 in __GI_abort () at abort.c​:79
#2 0x00007ffff7c2540f in __assert_fail_base (fmt=0x7ffff7d87ee0
"%s%s%s​:%u​: %s%sAssertion `%s' failed.\n%n", assertion=0x555555abc233
"0",
  file=0x555555aab720 "sv.c", line=12497, function=<optimized out>)
at assert.c​:92
#3 0x00007ffff7c330f2 in __GI___assert_fail (assertion=0x555555abc233
"0", file=0x555555aab720 "sv.c", line=12497,
  function=0x555555abe790 <__PRETTY_FUNCTION__.23329>
"Perl_sv_vcatpvfn_flags") at assert.c​:101
#4 0x00005555557d4738 in Perl_sv_vcatpvfn_flags (sv=0x555555b730c8,
pat=0x555555959ea9 "near \"%d%lu%4p\"\n", patlen=16,
args=0x7fffffffd7d0, svargs=0x0,
  sv_count=0, maybe_tainted=0x0, flags=130) at sv.c​:12497
#5 0x00005555557cfb68 in Perl_sv_catpvf (sv=0x555555b730c8,
pat=0x555555959ea9 "near \"%d%lu%4p\"\n") at sv.c​:10895
#6 0x00005555556670a3 in Perl_yyerror_pvn (s=0x555555960adf "syntax
error", len=12, flags=0) at toke.c​:11832
#7 0x000055555566684e in Perl_yyerror (s=0x555555960adf "syntax
error") at toke.c​:11737
#8 0x00005555556705df in Perl_yyparse (gramtype=258) at perly.c​:474
#9 0x00005555558390a9 in S_doeval_compile (gimme=1 '\001',
outside=0x555555b4e8f0, seq=4294967246, hh=0x0) at pp_ctl.c​:3502
#10 0x0000555555840e44 in Perl_pp_entereval () at pp_ctl.c​:4478
#11 0x000055555570b895 in Perl_runops_debug () at dump.c​:2537
#12 0x00005555555ed560 in S_run_body (oldscope=1) at perl.c​:2716
#13 0x00005555555ecade in perl_run (my_perl=0x555555b4c260) at perl.c​:2639
#14 0x00005555555a114e in main (argc=2, argv=0x7fffffffe1c8,
env=0x7fffffffe1e0) at perlmain.c​:127

This assertion was added by the following commit, but the current code
works around this situation on non-debugging builds

commit 79980e0
Author​: Jarkko Hietaniemi <jhi@​iki.fi>
Date​: Wed Sep 10 19​:42​:38 2014 -0400

  Also protect against elen < 0.

Perl Info

Flags:
    category=core
    severity=low

Site configuration information for perl 5.29.9:

Configured by dur-randir at Wed Feb 27 14:51:01 MSK 2019.

Summary of my perl5 (revision 5 version 29 subversion 9) configuration:
  Commit id: c1e47bad34ce1d9c84ed57c9b8978bcbd5a02e98
  Platform:
    osname=darwin
    osvers=13.4.0
    archname=darwin-thread-multi-2level
    uname='darwin isengard.local 13.4.0 darwin kernel version 13.4.0:
mon jan 11 18:17:34 pst 2016; root:xnu-2422.115.15~1release_x86_64
x86_64 '
    config_args='-de -Dusedevel -DDEBUGGING -Dusethreads'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='cc'
    ccflags ='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.9
-DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -DPERL_USE_SAFE_PUTENV'
    optimize='-O3 -g'
    cppflags='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.9
-DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include'
    ccversion=''
    gccversion='4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.56)'
    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 =' -mmacosx-version-min=10.9 -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/6.0/lib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib
/usr/lib
    libs=-lpthread -lgdbm -ldbm -ldl -lm -lutil -lc
    perllibs=-lpthread -ldl -lm -lutil -lc
    libc=
    so=dylib
    useshrplib=false
    libperl=libperl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=bundle
    d_dlsymun=undef
    ccdlflags=' '
    cccdlflags=' '
    lddlflags=' -mmacosx-version-min=10.9 -bundle -undefined
dynamic_lookup -L/usr/local/lib -fstack-protector'



@INC for perl 5.29.9:
    lib
    /usr/local/lib/perl5/site_perl/5.29.9/darwin-thread-multi-2level
    /usr/local/lib/perl5/site_perl/5.29.9
    /usr/local/lib/perl5/5.29.9/darwin-thread-multi-2level
    /usr/local/lib/perl5/5.29.9


Environment for perl 5.29.9:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/dur-randir
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/Users/dur-randir/perlbrew/bin:/Users/dur-randir/perlbrew/perls/perl-5.22.1/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/texbin
    PERLBREW_HOME=/Users/dur-randir/.perlbrew
    PERLBREW_MANPATH=/Users/dur-randir/perlbrew/perls/perl-5.22.1/man
    PERLBREW_PATH=/Users/dur-randir/perlbrew/bin:/Users/dur-randir/perlbrew/perls/perl-5.22.1/bin
    PERLBREW_PERL=perl-5.22.1
    PERLBREW_ROOT=/Users/dur-randir/perlbrew
    PERLBREW_SHELLRC_VERSION=0.84
    PERLBREW_VERSION=0.84
    PERL_BADLANG (unset)
    SHELL=/usr/local/bin/zsh