[Bug libdw/28660] New: ASan seems to complain about a "heap-buffer-overflow"

[Bug libdw/28660] New: ASan seems to complain about a "heap-buffer-overflow"

[evvers at ya dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

            Bug ID: 28660
           Summary: ASan seems to complain about a "heap-buffer-overflow"
           Product: elfutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libdw
          Assignee: unassigned at sourceware dot org
          Reporter: evvers at ya dot ru
                CC: elfutils-devel at sourceware dot org
  Target Milestone: ---

Created attachment 13826
  --> https://sourceware.org/bugzilla/attachment.cgi?id=13826&action=edit
File triggering a heap-buffer-overflow

One of systemd fuzz targets triggered a "heap-buffer-overflow". It can be
reproduced by building the master branch of the elfutils repository with ASan
and passing the attachment to `./src/stack`:
```
$ git describe
elfutils-0.186-7-g99782bd2

autoreconf -i -f
./configure --enable-maintainer-mode CFLAGS='-g -O1 -fno-omit-frame-pointer
-fsanitize=address' CXXFLAGS='-g -O1 -fno-omit-frame-pointer
-fsanitize=address'
ASAN_OPTIONS=detect_leaks=0 make -j$(nproc) V=1
LD_PRELOAD="/lib64/libasan.so.6 ./libelf/libelf.so ./libdw/libdw.so"
UBSAN_OPTIONS=print_stacktrace=1:print_summary=1  ./src/stack --core
../oss-fuzz-41566
=================================================================
==85112==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x602000001b70 at pc 0x7f96b3109a31 bp 0x7ffebaf7f470 sp 0x7ffebaf7f468
READ of size 4 at 0x602000001b70 thread T0
    #0 0x7f96b3109a30 in dwfl_link_map_report
/home/vagrant/elfutils/libdwfl/link_map.c:904
    #1 0x7f96b310e877 in _new.dwfl_core_file_report
/home/vagrant/elfutils/libdwfl/core-file.c:548
    #2 0x4037b8 in parse_opt /home/vagrant/elfutils/src/stack.c:595
    #3 0x7f96b2d05f81 in __argp_parse (/lib64/libc.so.6+0x10cf81)
    #4 0x404b7d in main /home/vagrant/elfutils/src/stack.c:695
    #5 0x7f96b2c20b74 in __libc_start_main (/lib64/libc.so.6+0x27b74)
    #6 0x40256d in _start (/home/vagrant/elfutils/src/stack+0x40256d)

0x602000001b71 is located 0 bytes to the right of 1-byte region
[0x602000001b70,0x602000001b71)
allocated by thread T0 here:
    #0 0x7f96b32b693f in __interceptor_malloc (/lib64/libasan.so.6+0xae93f)
    #1 0x7f96b31096c4 in dwfl_link_map_report
/home/vagrant/elfutils/libdwfl/link_map.c:879
    #2 0x7f96b310e877 in _new.dwfl_core_file_report
/home/vagrant/elfutils/libdwfl/core-file.c:548
    #3 0x4037b8 in parse_opt /home/vagrant/elfutils/src/stack.c:595
    #4 0x7f96b2d05f81 in __argp_parse (/lib64/libc.so.6+0x10cf81)
    #5 0x404b7d in main /home/vagrant/elfutils/src/stack.c:695
    #6 0x7f96b2c20b74 in __libc_start_main (/lib64/libc.so.6+0x27b74)

SUMMARY: AddressSanitizer: heap-buffer-overflow
/home/vagrant/elfutils/libdwfl/link_map.c:904 in dwfl_link_map_report
Shadow bytes around the buggy address:
  0x0c047fff8310: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8320: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8330: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8340: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8350: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
=>0x0c047fff8360: fa fa 00 03 fa fa 00 04 fa fa 00 04 fa fa[01]fa
  0x0c047fff8370: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8380: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8390: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff83a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff83b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==85112==ABORTING
```

It was also reported in
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=41566

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at klomp dot org

--- Comment #1 from Mark Wielaard <mark at klomp dot org> ---
Valgrind also complains about this.
But this seems to be resolved by the proposed patch for PR28657.
https://sourceware.org/bugzilla/show_bug.cgi?id=28657
Which makes sense since we aren't trying to deal with a zero phdr size.

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[evvers at ya dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

--- Comment #2 from Evgeny Vereshchagin <evvers at ya dot ru> ---
As far as I can see both issues are gone with that patch applied. Thanks!

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[evvers at ya dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

--- Comment #3 from Evgeny Vereshchagin <evvers at ya dot ru> ---
Looks like it keeps popping up with all the patches applied
```
0a2c8345 libdwfl: Don't try to convert too many dyns in dwfl_link_map_report
ea8ce550 libdwfl: Don't install an Elf handle in a Dwfl_Module twice
906e0ca5 libdwfl: Don't trust e_shentsize in dwfl_segment_report_module
a5dc98be libdwfl: Make sure we know the phdr entry size before searching phdrs.
8ae296dc libdwfl: Add overflow check while iterating in
dwfl_segment_report_module
c0dd1c35 libdwfl: Don't try to convert too many bytes in dwfl_link_map_report
5ba884a5 configure: Add --enable-sanitize-address
```
I'll attach a file triggering it once the fuzz target runs into it again

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[evvers at ya dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

--- Comment #4 from Evgeny Vereshchagin <evvers at ya dot ru> ---
Created attachment 13842
  --> https://sourceware.org/bugzilla/attachment.cgi?id=13842&action=edit
File triggering an "invalid read"

I've just attached a file triggering the issue:

```
autoreconf -i -f
./configure --enable-maintainer-mode
make -j$(nproc) V=1
DEBUGINFOD_URLS= LD_PRELOAD="./libelf/libelf.so ./libdw/libdw.so" valgrind
--leak-check=full ./src/stack --core
../crash-e8e47de6a28b1be30e3a7e2f92b7c9e4f4fffa9d
==87229== Memcheck, a memory error detector
==87229== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==87229== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==87229== Command: ./src/stack --core
../crash-e8e47de6a28b1be30e3a7e2f92b7c9e4f4fffa9d
==87229==
==87229== Invalid read of size 4
==87229==    at 0x48C783F: dwfl_link_map_report (link_map.c:917)
==87229==    by 0x48C8DC5: dwfl_core_file_report@@ELFUTILS_0.158
(core-file.c:548)
==87229==    by 0x402EC6: parse_opt (stack.c:595)
==87229==    by 0x4C4D591: argp_parse (in /usr/lib64/libc.so.6)
==87229==    by 0x4024EA: main (stack.c:695)
==87229==  Address 0x5029ae0 is 0 bytes after a block of size 4,096 alloc'd
==87229==    at 0x484186F: malloc (vg_replace_malloc.c:381)
==87229==    by 0x48C7D6B: dwfl_link_map_report (link_map.c:891)
==87229==    by 0x48C8DC5: dwfl_core_file_report@@ELFUTILS_0.158
(core-file.c:548)
==87229==    by 0x402EC6: parse_opt (stack.c:595)
==87229==    by 0x4C4D591: argp_parse (in /usr/lib64/libc.so.6)
==87229==    by 0x4024EA: main (stack.c:695)
```

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at sourceware dot org   |mark at klomp dot org
   Last reconfirmed|                            |2021-12-15
     Ever confirmed|0                           |1

--- Comment #5 from Mark Wielaard <mark at klomp dot org> ---
Proposed some more sanity checks:
https://sourceware.org/pipermail/elfutils-devel/2021q4/004523.html

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[evvers at ya dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

--- Comment #6 from Evgeny Vereshchagin <evvers at ya dot ru> ---
Thanks! I can confirm that the issue is gone.

I tested it in https://github.com/evverx/elfutils/pull/53 by adding that file
to the testsuite in
https://github.com/evverx/elfutils/pull/53/commits/38c241bf6269ab5a1dd93b606e11001dc3b6c1f4.
I also ran the fuzzer for about 10 minutes.

Interestingly, something started to trigger unreproducible MSan crashes but I'm
inclined to say it was probably a fluke.

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[evvers at ya dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

--- Comment #7 from Evgeny Vereshchagin <evvers at ya dot ru> ---
> Interestingly, something started to trigger unreproducible MSan crashes but
> I'm inclined to say it was probably a fluke.

It wasn't a glitch. The file I added to the test suite was also automatically
added to the seed corpus, which in turn triggered new code paths and led to
large allocations I reported elsewhere. So it doesn't have anything to do with
this issue and the patch.

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[Bug libdw/28660] ASan seems to complain about a "heap-buffer-overflow"

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #8 from Mark Wielaard <mark at klomp dot org> ---
Thanks for testing. Pushed as:

commit 3c9b69161b842708b4ef2f4e0f0b3ad1812798c2
Author: Mark Wielaard <mark@klomp.org>
Date:   Thu Dec 16 00:29:22 2021 +0100

    libdwfl: Make sure phent is sane and there is at least one phdr

    dwfl_link_map_report can only handle program headers that are the
    correct (32 or 64 bit) size. The buffer read in needs to contain room
    for at least one Phdr.

    https://sourceware.org/bugzilla/show_bug.cgi?id=28660

    Signed-off-by: Mark Wielaard <mark@klomp.org>

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