gdb log of crashed "btrfs-image -s"

[Christoph Groth <christoph@grothesque.org>]

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Christoph Groth wrote:
> Chris Murphy wrote:
>> On Tue, Jan 17, 2017 at 1:25 PM, Christoph Groth
>> <christoph@grothesque.org> wrote:
>>> Any ideas on what could be done?  If you need help to debug 
>>> the problem with
>>> btrfs-image, please tell me what I should do.  I can keep the 
>>> broken file
>>> system around until an image can be created at some later 
>>> time.
>>
>> Try 4.9, or even 4.8.5, tons of bugs have been fixed since 
>> 4.7.3
>> although I don't know off hand if this particular bug is 
>> fixed. I did
>> recently do a btrfs-image with btrfs-progs v4.9 with -s and did 
>> not
>> get a segfault.
>
> I compiled btrfs-image.static from btrfs-tools 4.9 (from git) 
> and started it from Debian testing's initramfs.  The exact 
> command that I use is:
>
> /mnt/btrfs-image.static -c3 -s /dev/sda2 /mnt/mim-s.bim
>
> It runs for a couple of seconds (enough to write 20263936 bytes 
> of output) and then quits with
>
> *** Error in `/mnt/btrfs-image.static`: double free or 
> corruption  (!prev): 0x00000000009f0940 ***
> ====== Backtrace: ======
> [0x45fb97]
> [0x465442]
> [0x465c1e]
> [0x402694]
> [0x402dcb]
> [0x4031fe]
> [0x4050ff]
> [0x405783]
> [0x44cb73]
> [0x44cdfe]
> [0x400b2a]
>
> (I had to type the above off the other screen, but I double 
> checked that there are no errors.)
>
> The executable that I used can be downloaded from 
> http://groth.fr/btrfs-image.static
> Its md5sum is 48abbc82ac6d3c0cb88cba1e5edb85fd.
>
> I hope that this can help someone to see what's going on.

I ran the same executable under gdb from a live system.  The log 
is attached.


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root@xubuntu:/media/xubuntu/wd1t# gdb btrfs-image.static
GNU gdb (Ubuntu 7.11-0ubuntu1) 7.11
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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Type "show configuration" for configuration details.
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<http://www.gnu.org/software/gdb/bugs/>.
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Reading symbols from btrfs-image.static...done.
(gdb) run -c3 -s /dev/sda2 /media/xubuntu/wd1t/mim-s.bim
Starting program: /media/xubuntu/wd1t/btrfs-image.static -c3 -s /dev/sda2 /media/xubuntu/wd1t/mim-s.bim
[New LWP 2334]
[New LWP 2335]
[New LWP 2336]
[New LWP 2337]
*** Error in `/media/xubuntu/wd1t/btrfs-image.static': free(): invalid next size (normal): 0x0000000000762570 ***
======= Backtrace: =========
[0x45fb97]
[0x465442]
[0x465c1e]
[0x402dea]
[0x4031fe]
[0x4050ff]
[0x405783]
[0x44cb73]
[0x44cdfe]
[0x400b2a]
======= Memory map: ========
00400000-00521000 r-xp 00000000 08:31 689                                /media/xubuntu/wd1t/btrfs-image.static
00721000-00728000 rw-p 00121000 08:31 689                                /media/xubuntu/wd1t/btrfs-image.static
00728000-0085b000 rw-p 00000000 00:00 0                                  [heap]
7fffe0000000-7fffe01aa000 rw-p 00000000 00:00 0 
7fffe01aa000-7fffe4000000 ---p 00000000 00:00 0 
7fffe4000000-7fffe4025000 rw-p 00000000 00:00 0 
7fffe4025000-7fffe8000000 ---p 00000000 00:00 0 
7fffe8000000-7fffe8186000 rw-p 00000000 00:00 0 
7fffe8186000-7fffec000000 ---p 00000000 00:00 0 
7fffec000000-7fffec195000 rw-p 00000000 00:00 0 
7fffec195000-7ffff0000000 ---p 00000000 00:00 0 
7ffff0000000-7ffff01b0000 rw-p 00000000 00:00 0 
7ffff01b0000-7ffff4000000 ---p 00000000 00:00 0 
7ffff5ff6000-7ffff5ff7000 rw-p 00000000 00:00 0 
7ffff5ff7000-7ffff5ff8000 ---p 00000000 00:00 0 
7ffff5ff8000-7ffff67f8000 rw-p 00000000 00:00 0 
7ffff67f8000-7ffff67f9000 ---p 00000000 00:00 0 
7ffff67f9000-7ffff6ff9000 rw-p 00000000 00:00 0 
7ffff6ff9000-7ffff6ffa000 ---p 00000000 00:00 0 
7ffff6ffa000-7ffff77fa000 rw-p 00000000 00:00 0 
7ffff77fa000-7ffff77fb000 ---p 00000000 00:00 0 
7ffff77fb000-7ffff7ffb000 rw-p 00000000 00:00 0 
7ffff7ffb000-7ffff7ffd000 r--p 00000000 00:00 0                          [vvar]
7ffff7ffd000-7ffff7fff000 r-xp 00000000 00:00 0                          [vdso]
7ffffffde000-7ffffffff000 rw-p 00000000 00:00 0                          [stack]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

Thread 1 "btrfs-image.sta" received signal SIGABRT, Aborted.
0x00000000004521de in raise ()
(gdb) bt
#0  0x00000000004521de in raise ()
#1  0x00000000004523aa in abort ()
#2  0x000000000045fb9c in __libc_message ()
#3  0x0000000000465442 in malloc_printerr ()
#4  0x0000000000465c1e in _int_free ()
#5  0x0000000000402dea in sanitize_name (slot=<optimized out>, key=<synthetic pointer>, src=<optimized out>, dst=0x76c690 "4\246", <incomplete sequence \367\261>, 
    md=<optimized out>) at image/main.c:574
#6  zero_items (src=0x760450, dst=0x76c690 "4\246", <incomplete sequence \367\261>, md=<optimized out>) at image/main.c:602
#7  copy_buffer (src=0x760450, dst=0x76c690 "4\246", <incomplete sequence \367\261>, md=<optimized out>) at image/main.c:645
#8  flush_pending (md=md@entry=0x7fffffffddc0, done=done@entry=0) at image/main.c:983
#9  0x00000000004031fe in add_extent (start=start@entry=192593920, size=size@entry=4096, md=md@entry=0x7fffffffddc0, data=data@entry=0) at image/main.c:1025
#10 0x00000000004050ff in copy_from_extent_tree (path=0x7fffffffe390, metadump=0x7fffffffddc0) at image/main.c:1280
#11 create_metadump (input=input@entry=0x7fffffffe851 "/dev/sda2", out=out@entry=0x731be0, num_threads=num_threads@entry=4, compress_level=compress_level@entry=3, 
    sanitize=sanitize@entry=1, walk_trees=walk_trees@entry=0) at image/main.c:1370
#12 0x0000000000405783 in main (argc=<optimized out>, argv=0x7fffffffe5d8) at image/main.c:2855

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