hg clone fails with error "double free or corruption (!prev)" on cifs-share

`hg clone http://hg.netbeans.org/main-golden/` fails iff it's invoked on a cifs-share with the error `*** Error in `/usr/bin/python': double free or corruption (!prev): 0x00000000023168d0 ***`. It works fine when invoked in a normal btrfs directory. The issue is reproducible

A `gdb` backtrace:

    #0 0x00007ffff761c267 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:55
    #1 0x00007ffff761deca in __GI_abort () at abort.c:89
    #2 0x00007ffff765fc53 in __libc_message (do_abort=do_abort@entry=1, fmt=fmt@entry=0x7ffff77781a8 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175
    #3 0x00007ffff7667c69 in malloc_printerr (ptr=<optimized out>, str=0x7ffff77782d8 "double free or corruption (!prev)", action=1) at malloc.c:4965
    #4 _int_free (av=<optimized out>, p=<optimized out>, have_lock=0) at malloc.c:3834
    #5 0x00007ffff766b89c in __GI___libc_free (mem=<optimized out>) at malloc.c:2950
    #6 0x00007ffff19d3e11 in lfree (a=a@entry=0xdc8e50) at mercurial/mpatch.c:67
    #7 0x00007ffff19d42e7 in decode (len=126, bin=0xe4b6c8 "") at mercurial/mpatch.c:228
    #8 fold (bins=[<buffer at remote 0x7ffff17c70f0>], start=start@entry=0, end=end@entry=1) at mercurial/mpatch.c:296
    #9 0x00007ffff19d43d3 in patches (self=<optimized out>, args=<optimized out>) at mercurial/mpatch.c:327
    #10 0x00000000004ccd05 in call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4035
    #11 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #12 0x00000000004cd4e2 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4121
    #13 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #14 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #15 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #16 0x00000000004ce7d3 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #17 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #18 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #19 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #20 0x00000000004ce7d3 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #21 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #22 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #23 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #24 0x00000000004ce7d3 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #25 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #26 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #27 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #28 0x00000000004cd217 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #29 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #30 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #31 0x00000000004cd4e2 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4121
    #32 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #33 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #34 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #35 0x00000000004cd217 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #36 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #37 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #38 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #39 0x00000000004cd217 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #40 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #41 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #42 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #43 0x00000000004cd217 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #44 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #45 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #46 0x00000000004e7cc8 in PyEval_EvalCodeEx (closure=<optimized out>, defcount=<optimized out>, defs=<optimized out>, kwcount=<optimized out>, kws=<optimized out>,
        argcount=<optimized out>, args=<optimized out>, locals=<optimized out>, globals=<optimized out>, co=<optimized out>) at ../Python/ceval.c:3267
    #47 function_call.lto_priv () at ../Objects/funcobject.c:526
    #48 0x00000000004cf239 in PyObject_Call (kw=<optimized out>, arg=<optimized out>, func=<optimized out>) at ../Objects/abstract.c:2529
    #49 ext_do_call (nk=<optimized out>, na=<optimized out>, flags=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4348
    #50 PyEval_EvalFrameEx () at ../Python/ceval.c:2720
    #51 0x00000000004e7cc8 in PyEval_EvalCodeEx (closure=<optimized out>, defcount=<optimized out>, defs=<optimized out>, kwcount=<optimized out>, kws=<optimized out>,
        argcount=<optimized out>, args=<optimized out>, locals=<optimized out>, globals=<optimized out>, co=<optimized out>) at ../Python/ceval.c:3267
    ---Type <return> to continue, or q <return> to quit---
    #52 function_call.lto_priv () at ../Objects/funcobject.c:526
    #53 0x00000000004cf239 in PyObject_Call (kw=<optimized out>, arg=<optimized out>, func=<optimized out>) at ../Objects/abstract.c:2529
    #54 ext_do_call (nk=<optimized out>, na=<optimized out>, flags=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4348
    #55 PyEval_EvalFrameEx () at ../Python/ceval.c:2720
    #56 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #57 0x00000000004ce7d3 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #58 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #59 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #60 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #61 0x00000000004ce7d3 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #62 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #63 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #64 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #65 0x00000000004ce7d3 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #66 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #67 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #68 0x00000000004cd4e2 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4121
    #69 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #70 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #71 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #72 0x00000000004ce7d3 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4131
    #73 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #74 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #75 0x00000000004cd4e2 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4121
    #76 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #77 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #78 0x00000000004cd4e2 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4121
    #79 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #80 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #81 0x00000000004cd4e2 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=<optimized out>, func=<optimized out>) at ../Python/ceval.c:4121
    #82 call_function (oparg=<optimized out>, pp_stack=<optimized out>) at ../Python/ceval.c:4056
    #83 PyEval_EvalFrameEx () at ../Python/ceval.c:2681
    #84 0x00000000004cb6b1 in PyEval_EvalCodeEx () at ../Python/ceval.c:3267
    #85 0x000000000050481f in PyEval_EvalCode (
        locals={'fp': <file at remote 0x7ffff7fd81e0>, 'demandimport': <module at remote 0x7ffff7e75ad0>, '__builtins__': <module at remote 0x7ffff7fb6b08>, 'mercurial': <module at remote 0x7ffff7e75788>, '__file__': '/usr/bin/hg', 'libdir': '@LIBDIR@', '__package__': None, 'sys': <module at remote 0x7ffff7fb6bb0>, '__name__': '__main__', 'os': <module at remote 0x7ffff7f89d00>, '__doc__': None},
        globals={'fp': <file at remote 0x7ffff7fd81e0>, 'demandimport': <module at remote 0x7ffff7e75ad0>, '__builtins__': <module at remote 0x7ffff7fb6b08>, 'mercurial': <module at remote 0x7ffff7e75788>, '__file__': '/usr/bin/hg', 'libdir': '@LIBDIR@', '__package__': None, 'sys': <module at remote 0x7ffff7fb6bb0>, '__name__': '__main__', 'os': <module at remote 0x7ffff7f89d00>, '__doc__': None}, co=0x7ffff7e5e5b0) at ../Python/ceval.c:669
    #86 run_mod.lto_priv () at ../Python/pythonrun.c:1371
    #87 0x00000000004fc182 in PyRun_FileExFlags () at ../Python/pythonrun.c:1357
    #88 0x00000000004fb247 in PyRun_SimpleFileExFlags () at ../Python/pythonrun.c:949
    #89 0x000000000049aa6e in Py_Main () at ../Modules/main.c:640
    #90 0x00007ffff7607a40 in __libc_start_main (main=0x49a500 <main>, argc=5, argv=0x7fffffffd2e8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>,
        stack_end=0x7fffffffd2d8) at libc-start.c:289
    #91 0x000000000049a429 in _start ()

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: mercurial 3.1.2-2
Uname: Linux 4.0.1-040001-generic x86_64
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Wed May 6 23:55:01 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-02 (34 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Beta amd64 (20150326)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: mercurial
SystemImageInfo:
 current build number: 0
 device name:
 channel: daily
 last update: Unknown
UpgradeStatus: No upgrade log present (probably fresh install)
---
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
DistroRelease: Ubuntu 15.04
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-02 (34 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Beta amd64 (20150326)
Package: mercurial 3.1.2-2
PackageArchitecture: amd64
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SystemImageInfo:
 current build number: 0
 device name:
 channel: daily
 last update: Unknown
Tags: vivid
Uname: Linux 4.0.1-040001-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm bumblebee cdrom dip libvirtd lpadmin plugdev sambashare sudo
_MarkForUpload: True