From @dur-randir

Created by @dur-randir

While fuzzing perl v5.29.8-21-gde59f38ed9 built with afl and run
under libdislocator, I found the following program

printf q)%7000000000E)=>

to cause an assertion failure

perl: sv.c:13127: Perl_sv_vcatpvfn_flags: Assertion `elen >= width' 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=0x555555aa0f0e
"elen >= width",
file=0x555555a8ff60 "sv.c", line=13189, function=<optimized out>)
at assert.c:92
#3 0x00007ffff7c330f2 in __GI___assert_fail (assertion=0x555555aa0f0e
"elen >= width", file=0x555555a8ff60 "sv.c", line=13189,
function=0x555555aa33b0 <__PRETTY_FUNCTION__.23320>
"Perl_sv_vcatpvfn_flags") at assert.c:101
#4 0x00005555557c2b6b in Perl_sv_vcatpvfn_flags (sv=0x555555b2d740,
pat=0x555555b54950 "%7000000000E", patlen=12, args=0x0,
svargs=0x555555b2fdb0,
sv_count=0, maybe_tainted=0x7fffffffddd7, flags=0) at sv.c:13189
#5 0x00005555557bb9a8 in Perl_sv_vsetpvfn (sv=0x555555b2d740,
pat=0x555555b54950 "%7000000000E", patlen=12, args=0x0,
svargs=0x555555b2fdb0, sv_count=0,
maybe_tainted=0x7fffffffddd7) at sv.c:10977
#6 0x000055555586a67c in Perl_do_sprintf (sv=0x555555b2d740, len=1,
sarg=0x555555b2fda8) at doop.c:734
#7 0x00005555558485c3 in Perl_pp_prtf () at pp_sys.c:1628
#8 0x00005555556f6ff4 in Perl_runops_debug () at dump.c:2537
#9 0x00005555555da157 in S_run_body (oldscope=1) at perl.c:2692
#10 0x00005555555d96d5 in perl_run (my_perl=0x555555b2b260) at perl.c:2615
#11 0x000055555558e14e in main (argc=2, argv=0x7fffffffe1e8,
env=0x7fffffffe200) at perlmain.c:127

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

commit 5860c1e
Author: David Mitchell <davem@iabyn.com>
Date: Mon May 29 09:59:16 2017 +0100

S_expect_number(): return STRLEN not I32

This static function is used by Perl_sv_vcatpvfn_flags() to read in
a width or explicit argument number. It currently returns an I32 result
(and croaks if the number exceeds the maximum possible I32 value).

Change it to return STRLEN, and to croak on the value being greater than
max(STRLEN) / 4.

Perl Info


Flags:
    category=core
    severity=medium

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

Assertion failure in Perl_sv_vcatpvfn_flags (sv.c:13127) #16881

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