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Id: 128255
Status: resolved
Priority: 0/
Queue: perl5

Owner: Nobody
Requestors: dcollinsn [at]

Operating System: (no value)
PatchStatus: (no value)
Severity: low
Type: unknown
Perl Version: (no value)
Fixed In: 5.25.3

Subject: Assert fail in S_sublex_done without other symptoms
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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:~/perl$ ./perl -Ilib /usr/local/perl-afl/out/allcrash/f1i000029 Use of comma-less variable list is deprecated at /usr/local/perl-afl/out/allcrash/f1i000029 line 3. Final $ should be \$ or $name at /usr/local/perl-afl/out/allcrash/f1i000029 line 3, within string syntax error at /usr/local/perl-afl/out/allcrash/f1i000029 line 3, next char / Format not terminated at /usr/local/perl-afl/out/allcrash/f1i000029 line 4, at end of line syntax error at /usr/local/perl-afl/out/allcrash/f1i000029 line 4, at EOF Execution of /usr/local/perl-afl/out/allcrash/f1i000029 aborted due to compilation errors. dcollins@nightshade64:~/perl$ cd ../perldebug/ dcollins@nightshade64:~/perldebug$ ./perl -Ilib /usr/local/perl-afl/out/allcrash/f1i000029 Use of comma-less variable list is deprecated at /usr/local/perl-afl/out/allcrash/f1i000029 line 3. perl: toke.c:2450: S_sublex_done: Assertion `(PL_parser->lex_inwhat) == OP_SUBST || (PL_parser->lex_inwhat) == OP_TRANS' failed. Aborted dcollins@nightshade64:~/perldebug$ cat /usr/local/perl-afl/out/allcrash/f1i000029 format= @ 0"$"dcollins@nightshade64:~/perldebug$ od -c /usr/local/perl-afl/out/allcrash/f1i000029 0000000 f o r m a t = \n @ \n 0 " $ " 0000016 Debugging tool output is below. A git bisect was performed and reported the following. 5aa91856e21c93226d08f19eb69098f224de5fff is the first bad commit commit 5aa91856e21c93226d08f19eb69098f224de5fff Author: Father Chrysostomos <> Date: Mon Dec 30 21:18:54 2013 -0800 toke.c: Remove redundant check (and turn it into an assertion.) PL_lex_repl can only be set here if we are parsing a substitution (OP_SUBST) or transliteration (OP_TRANS). I believe this check has been unnecessary since perl 5.000, which it was added. :100644 100644 ca306f1455ba8f2c02acd3d7eff3e5490706de84 8ac0f31fb4f85c4ab453b52ec75f92900c448292 M toke.c bisect run success **GDB** dcollins@nightshade64:~/perldebug$ gdb --args ./miniperl -Ilib /usr/local/perl-afl/out/allcrash/f1i000029 GNU gdb (GDB) 7.10 Copyright (C) 2015 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <> 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: <>. Find the GDB manual and other documentation resources online at: <>. For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from ./miniperl...done. (gdb) run Starting program: /home/dcollins/perldebug/miniperl -Ilib /usr/local/perl-afl/out/allcrash/f1i000029 [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/". Use of comma-less variable list is deprecated at /usr/local/perl-afl/out/allcrash/f1i000029 line 3. miniperl: toke.c:2450: S_sublex_done: Assertion `(PL_parser->lex_inwhat) == OP_SUBST || (PL_parser->lex_inwhat) == OP_TRANS' failed. Program received signal SIGABRT, Aborted. 0x00007ffff6cf9478 in raise () from /lib/x86_64-linux-gnu/ (gdb) bt #0 0x00007ffff6cf9478 in raise () from /lib/x86_64-linux-gnu/ #1 0x00007ffff6cfa8fa in abort () from /lib/x86_64-linux-gnu/ #2 0x00007ffff6cf23a7 in ?? () from /lib/x86_64-linux-gnu/ #3 0x00007ffff6cf2452 in __assert_fail () from /lib/x86_64-linux-gnu/ #4 0x000000000047ea40 in S_sublex_done () at toke.c:2450 #5 0x000000000048b6d5 in Perl_yylex () at toke.c:4728 #6 0x00000000004ba030 in Perl_yyparse (gramtype=258) at perly.c:332 #7 0x00000000004475b4 in S_parse_body (env=0x0, xsinit=0x727694 <xs_init>) at perl.c:2365 #8 0x0000000000446052 in perl_parse (my_perl=0xa7f010, xsinit=0x727694 <xs_init>, argc=3, argv=0x7fffffffe5f8, env=0x0) at perl.c:1681 #9 0x00000000007275f3 in main (argc=3, argv=0x7fffffffe5f8, env=0x7fffffffe618) at miniperlmain.c:120 (gdb) f 4 #4 0x000000000047ea40 in S_sublex_done () at toke.c:2450 2450 assert (PL_lex_inwhat == OP_SUBST || PL_lex_inwhat == OP_TRANS); (gdb) l 2445 } 2446 2447 /* Is there a right-hand side to take care of? (s//RHS/ or tr//RHS/) */ 2448 assert(PL_lex_inwhat != OP_TRANSR); 2449 if (PL_lex_repl) { 2450 assert (PL_lex_inwhat == OP_SUBST || PL_lex_inwhat == OP_TRANS); 2451 PL_linestr = PL_lex_repl; 2452 PL_lex_inpat = 0; 2453 PL_bufend = PL_bufptr = PL_oldbufptr = PL_oldoldbufptr = PL_linestart = SvPVX(PL_linestr); 2454 PL_bufend += SvCUR(PL_linestr); **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, 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 .
Date: Fri, 8 Jul 2016 09:56:27 +0100
To: perl5-porters [...]
From: Dave Mitchell <davem [...]>
Subject: Re: [perl #128255] Assert fail in S_sublex_done without other symptoms
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On Thu, May 26, 2016 at 05:45:05PM -0700, Dan Collins wrote: Show quoted text
> dcollins@nightshade64:~/perldebug$ ./perl -Ilib /usr/local/perl-afl/out/allcrash/f1i000029 > Use of comma-less variable list is deprecated at /usr/local/perl-afl/out/allcrash/f1i000029 line 3. > perl: toke.c:2450: S_sublex_done: Assertion `(PL_parser->lex_inwhat) == OP_SUBST || (PL_parser->lex_inwhat) == OP_TRANS' failed. > Aborted > > dcollins@nightshade64:~/perldebug$ cat /usr/local/perl-afl/out/allcrash/f1i000029 > format= > @
Fixed by the below: commit 59a08c763def19a317f229e4a95b1cdf6db8e12d Author: David Mitchell <> AuthorDate: Fri Jul 8 09:48:04 2016 +0100 Commit: David Mitchell <> CommitDate: Fri Jul 8 09:48:04 2016 +0100 RT #128255: Assert fail in S_sublex_done Some code that handles deprecated behaviour in formats was triggering an assertion. This: format STDOUT = @ 0"$x" gave this warning: Use of comma-less variable list is deprecated but then gave this panic: toke.c:2457: S_sublex_done: Assertion `(PL_parser->lex_inwhat) == OP_SUBST || (PL_parser->lex_inwhat) == OP_TRANS' failed. This is due to the lexer calling scan_str(), then backing off and doing the warning and returning a comma, then on the next token get, calling scan_str() again. Because scan_str() has been called twice, the second time it extracts the string to PL_sublex_info.repl rather than PL_lex_stuff, as it does with things like s/foo/bar/ and tr/abc/ABC/. Later an assert that PL_sublex_info.repl is only set for a s/// or tr/// fails. The solution seems to be to check and return a comma *before* trying to call scan_str(). -- I before E. Except when it isn't.
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