Assertion failure in S_maybe_multideref (op.c:14912)

[p5pRT]

Migrated from rt.perl.org#134045 (status was 'pending release')

Searchable as RT134045$

[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

0for%{scalar local$0[0]}

to cause an assertion failure

perl​: op.c​:14912​: void S_maybe_multideref(OP *, OP *, UV, U8)​:
Assertion `n && n->op_type == OP_LEAVE' 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=0x55555592a9c3 "n && n->op_type == OP_LEAVE",
file=0x5555559247ae "op.c", line=14892, function=<optimized out>) at
assert.c​:92
#3 0x00007ffff7c330f2 in __GI___assert_fail (assertion=0x55555592a9c3
"n && n->op_type == OP_LEAVE", file=0x5555559247ae "op.c", line=14892,
  function=0x55555592ccc0 <__PRETTY_FUNCTION__.22939>
"S_maybe_multideref") at assert.c​:101
#4 0x00005555555deedc in S_maybe_multideref (start=0x555555b79648,
orig_o=0x555555b795c8, orig_action=6, hints=0 '\000') at op.c​:14892
#5 0x00005555555e0146 in Perl_rpeep (o=0x555555b79648) at op.c​:15545
#6 0x00005555555e37da in Perl_peep (o=0x555555b7b358) at op.c​:16627
#7 0x00005555555ac110 in S_process_optree (cv=0x0,
optree=0x555555b7b390, start=0x555555b7b358) at op.c​:3459
#8 0x00005555555b3f02 in Perl_newPROG (o=0x555555b7b390) at op.c​:5413
#9 0x000055555566c1b0 in Perl_yyparse (gramtype=258) at perly.y​:125
#10 0x00005555555ec726 in S_parse_body (env=0x0, xsinit=0x5555555a11f8
<xs_init>) at perl.c​:2531
#11 0x00005555555ea9f8 in perl_parse (my_perl=0x555555b4e260,
xsinit=0x5555555a11f8 <xs_init>, argc=3, argv=0x7fffffffe1b8, env=0x0)
at perl.c​:1822
#12 0x00005555555a113b in main (argc=3, argv=0x7fffffffe1b8,
env=0x7fffffffe1d8) at perlmain.c​:126

This is a regression between 5.20 and 5.22, bisect points to

commit fedf30e
Author​: David Mitchell <davem@​iabyn.com>
Date​: Fri Oct 24 16​:26​:38 2014 +0100

  Add OP_MULTIDEREF

  This op is an optimisation for any series of one or more array or hash
  lookups and dereferences, where the key/index is a simple constant or
  package/lexical variable. If the first-level lookup is of a simple
  array/hash variable or scalar ref, then that is included in the op too.

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

[p5pRT]

From @tonycoz

On Thu, 18 Apr 2019 09​:51​:12 -0700, randir wrote​:

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

0for%{scalar local$0[0]}

to cause an assertion failure

perl​: op.c​:14912​: void S_maybe_multideref(OP *, OP *, UV, U8)​:
Assertion `n && n->op_type == OP_LEAVE' 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=0x55555592a9c3 "n && n->op_type == OP_LEAVE",
file=0x5555559247ae "op.c", line=14892, function=<optimized out>) at
assert.c​:92
#3 0x00007ffff7c330f2 in __GI___assert_fail (assertion=0x55555592a9c3
"n && n->op_type == OP_LEAVE", file=0x5555559247ae "op.c", line=14892,
function=0x55555592ccc0 <__PRETTY_FUNCTION__.22939>
"S_maybe_multideref") at assert.c​:101
#4 0x00005555555deedc in S_maybe_multideref (start=0x555555b79648,
orig_o=0x555555b795c8, orig_action=6, hints=0 '\000') at op.c​:14892
#5 0x00005555555e0146 in Perl_rpeep (o=0x555555b79648) at op.c​:15545
#6 0x00005555555e37da in Perl_peep (o=0x555555b7b358) at op.c​:16627
#7 0x00005555555ac110 in S_process_optree (cv=0x0,
optree=0x555555b7b390, start=0x555555b7b358) at op.c​:3459
#8 0x00005555555b3f02 in Perl_newPROG (o=0x555555b7b390) at op.c​:5413
#9 0x000055555566c1b0 in Perl_yyparse (gramtype=258) at perly.y​:125
#10 0x00005555555ec726 in S_parse_body (env=0x0, xsinit=0x5555555a11f8
<xs_init>) at perl.c​:2531
#11 0x00005555555ea9f8 in perl_parse (my_perl=0x555555b4e260,
xsinit=0x5555555a11f8 <xs_init>, argc=3, argv=0x7fffffffe1b8, env=0x0)
at perl.c​:1822
#12 0x00005555555a113b in main (argc=3, argv=0x7fffffffe1b8,
env=0x7fffffffe1d8) at perlmain.c​:126

This is a regression between 5.20 and 5.22, bisect points to

commit fedf30e
Author​: David Mitchell <davem@​iabyn.com>
Date​: Fri Oct 24 16​:26​:38 2014 +0100

Add OP_MULTIDEREF

This op is an optimisation for any series of one or more array or hash
lookups and dereferences, where the key/index is a simple constant or
package/lexical variable. If the first-level lookup is of a simple
array/hash variable or scalar ref, then that is included in the op
too.

I think the check here should be bypassing the OP_SCALAR as it does OP_LIST.

Per the attached.

Tony

[p5pRT]

From @tonycoz

0001-perl-134048-prevent-an-erroneous-assertion-on-OP_SCA.patch

From d5eb166fb069cc1d53da26788049bf715cf68ba2 Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Wed, 24 Apr 2019 11:05:21 +1000
Subject: (perl #134048) prevent an erroneous assertion on OP_SCALAR

---
 op.c              | 3 ++-
 t/op/multideref.t | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/op.c b/op.c
index 1862f1b11b..a4bed9c582 100644
--- a/op.c
+++ b/op.c
@@ -14907,7 +14907,8 @@ S_maybe_multideref(pTHX_ OP *start, OP *orig_o, UV orig_action, U8 hints)
 #ifdef DEBUGGING
                     OP *n = o->op_next;
                     while (n && (  n->op_type == OP_NULL
-                                || n->op_type == OP_LIST))
+                                || n->op_type == OP_LIST
+                                || n->op_type == OP_SCALAR))
                         n = n->op_next;
                     assert(n && n->op_type == OP_LEAVE);
 #endif
diff --git a/t/op/multideref.t b/t/op/multideref.t
index 12b04536e5..23487ca283 100644
--- a/t/op/multideref.t
+++ b/t/op/multideref.t
@@ -18,7 +18,7 @@ BEGIN {
 use warnings;
 use strict;
 
-plan 64;
+plan 65;
 
 
 # check that strict refs hint is handled
@@ -242,3 +242,5 @@ sub defer {}
     ::pass("S_maybe_multideref() shouldn't leak on croak");
 }
 
+fresh_perl_is('0for%{scalar local$0[0]}', '', {},
+              "RT #134045 assertion on the OP_SCALAR");
-- 
2.11.0

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From @dur-randir

Can this patch be applied now?

[p5pRT]

From @tonycoz

On Sat, 25 May 2019 08​:17​:43 -0700, randir wrote​:

Can this patch be applied now?

Applied as 94a2f6a, thanks for the report.

Tony

[p5pRT]

@tonycoz - Status changed from 'open' to 'pending release'