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 progam

printf "%.*a", 1.84466502487128e+19,0

to cause unknown-crash write diagnostics by ASAN. GDB stack trace is following

S_format_hexfp (buf=0x555555b75b80 "0x0.", '0' <repeats 196 times>...,
bufsize=69, c=97 'a', nv=0, fv=0, has_precis=false,
precis=93824996751360, width=0,
alt=false, plus=0 '\000', left=false, fill=false) at sv.c:11792
11792 *p++ = '0';
(gdb) bt
#0 S_format_hexfp (buf=0x555555b75b80 "0x0.", '0' <repeats 196
times>..., bufsize=69, c=97 'a', nv=0, fv=0, has_precis=false,
precis=93824996751360,
width=0, alt=false, plus=0 '\000', left=false, fill=false) at sv.c:11792
#1 0x00005555557d6c1c in Perl_sv_vcatpvfn_flags (sv=0x555555b4e740,
pat=0x555555b75b10 "%.*a", patlen=4, args=0x0, svargs=0x555555b50db0,
sv_count=2,
maybe_tainted=0x7fffffffdd97, flags=0) at sv.c:13093
#2 0x00005555557cff0e in Perl_sv_vsetpvfn (sv=0x555555b4e740,
pat=0x555555b75b10 "%.*a", patlen=4, args=0x0, svargs=0x555555b50db0,
sv_count=2,
maybe_tainted=0x7fffffffdd97) at sv.c:10977
#3 0x000055555587eb55 in Perl_do_sprintf (sv=0x555555b4e740, len=3,
sarg=0x555555b50da8) at doop.c:734
#4 0x000055555585cad0 in Perl_pp_prtf () at pp_sys.c:1628
#5 0x000055555570b895 in Perl_runops_debug () at dump.c:2537
#6 0x00005555555ed560 in S_run_body (oldscope=1) at perl.c:2716
#7 0x00005555555ecade in perl_run (my_perl=0x555555b4c260) at perl.c:2639
#8 0x00005555555a114e in main (argc=3, argv=0x7fffffffe1a8,
env=0x7fffffffe1c8) at perlmain.c:127

This is a regression between 5.26 and 5.28, bisect points to:

commit 50a7222 (HEAD, refs/bisect/bad)
Author: David Mitchell <davem@iabyn.com>
Date: Tue May 30 13:45:35 2017 +0100

Perl_sv_vcatpvfn_flags: width/precis arg wrap

When the width or precision is specified via an argument rather than
literally, check whether the value wraps.

Perl Info


Flags:
    category=core
    severity=high

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

unknown-crash in S_format_hexfp #16942

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