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Segmentation fault in pack (S_pack_rec tries to access unallocated memory) #14977

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p5pRT opened this issue Oct 11, 2015 · 6 comments
Closed

Segmentation fault in pack (S_pack_rec tries to access unallocated memory) #14977

p5pRT opened this issue Oct 11, 2015 · 6 comments
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@p5pRT
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@p5pRT p5pRT commented Oct 11, 2015

Migrated from rt.perl.org#126325 (status was 'resolved')

Searchable as RT126325$

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@p5pRT p5pRT commented Oct 11, 2015

From @dcollinsn

Greetings Porters,

I have compiled bleadperl with the afl-gcc compiler using​:

./Configure -Dusedevel -Dprefix='/usr/local/perl-afl' -Dcc='ccache afl-gcc' -Duselongdouble -Duse64bitall -Doptimize=-g -Uversiononly -Uman1dir -Uman3dir -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 a segmentation fault in the perl interpreter. The testcase is the file​:

pack+WH200000,\0

Today I'm reporting a pair of bugs related to pack/unpack. They appeared to be related, but GDB shows that they have very different behaviours. This is by far the tamer of the two.

**GDB**

(gdb) run
Starting program​: /usr/local/perl-afl/bin/perl -e pack+WH200000,\\0
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
S_pack_rec (cat=0x0, cat@​entry=0x1205af0, symptr=0x2fcc0, beglist=0x1,
  beglist@​entry=0x11f3a30, endlist=0x7ffff7e1d015, endlist@​entry=0x11f3a38)
  at pp_pack.c​:2503
2503 } else if (isALPHA(*str))
(gdb) bt
#0 S_pack_rec (cat=0x0, cat@​entry=0x1205af0, symptr=0x2fcc0, beglist=0x1,
  beglist@​entry=0x11f3a30, endlist=0x7ffff7e1d015, endlist@​entry=0x11f3a38)
  at pp_pack.c​:2503
#1 0x0000000000eb2f5f in Perl_packlist (endlist=0x11f3a38,
  beglist=0x11f3a30, patend=<optimized out>, pat=<optimized out>,
  cat=0x1205af0) at pp_pack.c​:1971
#2 Perl_pp_pack () at pp_pack.c​:3128
#3 0x00000000007dec7f in Perl_runops_debug () at dump.c​:2224
#4 0x0000000000544469 in S_run_body (oldscope=1) at perl.c​:2456
#5 perl_run (my_perl=<optimized out>) at perl.c​:2379
#6 0x000000000042c6f8 in main (argc=3, argv=0x7fffffffe648,
  env=0x7fffffffe668) at perlmain.c​:116
(gdb) info locals
str = 0xfeb000 <error​: Cannot access memory at address 0xfeb000>
utf8_flags = 195775
fromlen = 0
howlen = e_number
lookahead = {patptr = 0x120e788 "", patend = 0x120e788 "", grpbeg = 0x0,
  grpend = 0x0, code = 72, length = 200000, howlen = e_number, level = 0,
  flags = 9, strbeg = 0, previous = 0x0}
utf8 = 207
__PRETTY_FUNCTION__ = "S_pack_rec"
(gdb) f 1
#1 0x0000000000eb2f5f in Perl_packlist (endlist=0x11f3a38,
  beglist=0x11f3a30, patend=<optimized out>, pat=<optimized out>,
  cat=0x1205af0) at pp_pack.c​:1971
1971 (void)pack_rec( cat, &sym, beglist, endlist );
(gdb) info locals
sym = {patptr = 0x120e788 "", patend = 0x120e788 "", grpbeg = 0x0,
  grpend = 0x0, code = 72, length = 200000, howlen = e_number, level = 0,
  flags = 9, strbeg = 0, previous = 0x0}

**VALGRIND**

==31388== Memcheck, a memory error detector
==31388== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==31388== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==31388== Command​: ../bin/perl -e pack+WH200000,\\0
==31388==
==31388== Invalid read of size 1
==31388== at 0xEA3014​: S_pack_rec (pp_pack.c​:2503)
==31388== by 0xEB2F5E​: Perl_packlist (pp_pack.c​:1971)
==31388== by 0xEB2F5E​: Perl_pp_pack (pp_pack.c​:3128)
==31388== by 0x7DEC7E​: Perl_runops_debug (dump.c​:2224)
==31388== by 0x544468​: S_run_body (perl.c​:2456)
==31388== by 0x544468​: perl_run (perl.c​:2379)
==31388== by 0x42C6F7​: main (perlmain.c​:116)
==31388== Address 0xfeb000 is not stack'd, malloc'd or (recently) free'd
==31388==
==31388==
==31388== Process terminating with default action of signal 11 (SIGSEGV)
==31388== Access not within mapped region at address 0xFEB000
==31388== at 0xEA3014​: S_pack_rec (pp_pack.c​:2503)
==31388== by 0xEB2F5E​: Perl_packlist (pp_pack.c​:1971)
==31388== by 0xEB2F5E​: Perl_pp_pack (pp_pack.c​:3128)
==31388== by 0x7DEC7E​: Perl_runops_debug (dump.c​:2224)
==31388== by 0x544468​: S_run_body (perl.c​:2456)
==31388== by 0x544468​: perl_run (perl.c​:2379)
==31388== by 0x42C6F7​: main (perlmain.c​:116)
==31388== If you believe this happened as a result of a stack
==31388== overflow in your program's main thread (unlikely but
==31388== possible), you can try to increase the size of the
==31388== main thread stack using the --main-stacksize= flag.
==31388== The main thread stack size used in this run was 8388608.
==31388==
==31388== HEAP SUMMARY​:
==31388== in use at exit​: 310,063 bytes in 540 blocks
==31388== total heap usage​: 639 allocs, 99 frees, 327,593 bytes allocated
==31388==
==31388== LEAK SUMMARY​:
==31388== definitely lost​: 176 bytes in 1 blocks
==31388== indirectly lost​: 1,989 bytes in 20 blocks
==31388== possibly lost​: 0 bytes in 0 blocks
==31388== still reachable​: 307,898 bytes in 519 blocks
==31388== suppressed​: 0 bytes in 0 blocks
==31388== Rerun with --leak-check=full to see details of leaked memory
==31388==
==31388== For counts of detected and suppressed errors, rerun with​: -v
==31388== ERROR SUMMARY​: 1 errors from 1 contexts (suppressed​: 0 from 0)
Segmentation fault

**PERL -V**

Summary of my perl5 (revision 5 version 23 subversion 4) configuration​:
  Commit id​: 94757bf
  Platform​:
  osname=linux, osvers=3.16.0-4-amd64, archname=x86_64-linux-ld
  uname='linux nightshade64 3.16.0-4-amd64 #1 smp debian 3.16.7-ckt11-1+deb8u4 (2015-09-19) x86_64 gnulinux '
  config_args='-Dusedevel -Dprefix=/usr/local/perl-afl -Dcc=ccache afl-gcc -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 afl-gcc', 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='4.9.2', 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 afl-gcc', ldflags =' -fstack-protector-strong -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.9/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
  libc=libc-2.19.so, so=so, useshrplib=false, libperl=libperl.a
  gnulibc_version='2.19'
  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_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 Sep 30 2015 16​:39​:59
  @​INC​:
  /usr/local/perl-afl/lib/site_perl/5.23.4/x86_64-linux-ld
  /usr/local/perl-afl/lib/site_perl/5.23.4
  /usr/local/perl-afl/lib/5.23.4/x86_64-linux-ld
  /usr/local/perl-afl/lib/5.23.4
  .

@p5pRT
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@p5pRT p5pRT commented Oct 22, 2015

From @tonycoz

On Sun Oct 11 04​:49​:37 2015, dcollinsn@​gmail.com wrote​:

After reducing testcases using `afl-tmin` and performing additional
minimization by hand, I have located the following testcase that
triggers a segmentation fault in the perl interpreter. The testcase is
the file​:

pack+WH200000,\0

The attached seems to fix it.

I'm going to review the other pack handlers to check for similar issues.

Tony

@p5pRT
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@p5pRT p5pRT commented Oct 22, 2015

From @tonycoz

0001-perl-126325-don-t-read-past-the-end-of-the-source-fo.patch
From 45f3993798e8339daceeb6b1a0ce606da9e8a613 Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Thu, 22 Oct 2015 12:03:05 +1100
Subject: [perl #126325] don't read past the end of the source for pack [Hh]

With a utf8 target but a non-utf8 source, pack Hh would read past the
end of the source when given a length, due to an incorrect condition.
---
 pp_pack.c   |  2 +-
 t/op/pack.t | 22 +++++++++++++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/pp_pack.c b/pp_pack.c
index 96dfd20..044ea7f 100644
--- a/pp_pack.c
+++ b/pp_pack.c
@@ -2488,7 +2488,7 @@ S_pack_rec(pTHX_ SV *cat, tempsym_t* symptr, SV **beglist, SV **endlist )
 	    if (howlen == e_star) len = fromlen;
 	    field_len = (len+1)/2;
 	    GROWING(utf8, cat, start, cur, field_len);
-	    if (!utf8 && len > (I32)fromlen) len = fromlen;
+	    if (!utf8_source && len > (I32)fromlen) len = fromlen;
 	    bits = 0;
 	    l = 0;
 	    if (datumtype == 'H')
diff --git a/t/op/pack.t b/t/op/pack.t
index e348693..a2da636 100644
--- a/t/op/pack.t
+++ b/t/op/pack.t
@@ -12,7 +12,7 @@ my $no_endianness = $] > 5.009 ? '' :
 my $no_signedness = $] > 5.009 ? '' :
   "Signed/unsigned pack modifiers not available on this perl";
 
-plan tests => 14708;
+plan tests => 14712;
 
 use strict;
 use warnings qw(FATAL all);
@@ -2024,3 +2024,23 @@ is $o::num, 1,     'pack "c" does call num overloading';
 #[perl #123874]: argument underflow leads to corrupt length
 eval q{ pack "pi/x" };
 ok(1, "argument underflow did not crash");
+
+{
+    # [perl #126325] pack [hH] with a unicode string
+    # the hex encoders would read past the end of the string, using
+    # invalid source bytes
+    my $twenty_nuls = "\0" x 20;
+    # This is the case that failed
+    is(pack("WH40", 0x100, ""), "\x{100}$twenty_nuls",
+       "check pack H zero fills (utf8 target)");
+    my $up_nul = "\0";
+
+    utf8::upgrade($up_nul);
+    # check the other combinations too
+    is(pack("WH40", 0x100, $up_nul), "\x{100}$twenty_nuls",
+       "check pack H zero fills (utf8 target/source)");
+    is(pack("H40", ""), $twenty_nuls,
+       "check pack H zero fills (utf8 none)");
+    is(pack("H40", $up_nul), $twenty_nuls,
+       "check pack H zero fills (utf8 source)");
+}
-- 
2.1.4

@p5pRT
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@p5pRT p5pRT commented Oct 22, 2015

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

@p5pRT
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@p5pRT p5pRT commented Nov 11, 2015

From @tonycoz

On Wed Oct 21 18​:05​:47 2015, tonyc wrote​:

On Sun Oct 11 04​:49​:37 2015, dcollinsn@​gmail.com wrote​:

After reducing testcases using `afl-tmin` and performing additional
minimization by hand, I have located the following testcase that
triggers a segmentation fault in the perl interpreter. The testcase is
the file​:

pack+WH200000,\0

The attached seems to fix it.

Pushed as 0403a1a.

I'm going to review the other pack handlers to check for similar issues.

The others seemed ok to me.

Tony

@p5pRT p5pRT closed this Nov 11, 2015
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@p5pRT p5pRT commented Nov 11, 2015

@tonycoz - Status changed from 'open' to 'resolved'

@p5pRT p5pRT added the Severity Low label Oct 19, 2019
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