proot: ./path/path.c:546: compare_paths2: Assertion `length1 > 0' failed.

[zaoqi]

Steps to Reproduce the Problem

do not mkdir tmp

1. fakechroot fakeroot chroot . ./proot/src/proot -R alpine-minirootfs-3.10.1-x86_64

Specifications

• Proot/Care version: commit 803e54d
• Kernel version: 4.19.56
• Host distribution: manjaro
• Guest distribution: alpine

[zaoqi]

if mkdir tmp

$ fakechroot fakeroot chroot . ./proot/src/proot -R alpine-minirootfs-3.10.1-x86_64
proot error: execve("/bin/sh"): No such file or directory
proot info: possible causes:
  * the program is a script but its interpreter (eg. /bin/sh) was not found;
  * the program is an ELF but its interpreter (eg. ld-linux.so) was not found;
  * the program is a foreign binary but qemu was not specified;
  * qemu does not work correctly (if specified);
  * the loader was not found or doesn't work.
fatal error: see `proot --help`.
proot error: can't chmod '/tmp/proot-22405-7CHcGd': No such file or directory
proot error: can't chdir to '/': No such file or directory

[oxr463]

Interesting.. I'll look into it.

Thanks for providing such detailed debugging information!

[0pq76r]

I had a similar issue. The problem is, that the detranslate_path function somehow is called with empty strings for path and/or t_referrer.

Also length1 and length2 are of type size_t, thus, unsigned integers and by the looks of it the case length1==0 is supposed to be handled in the if statement immediately after the assert.

There's probably a better way to fix it, but this works for me: 0pq76r/proot@7d7479c

[V6ser]

Still not fixed as of latest version.

[angelsl]

This is a bit tricky. At least one cause of this crash is when readlinkat is called with an empty string for the path, which is allowed: (see readlinkat(2))

Since Linux 2.6.39, pathname can be an empty string, in which case the call operates on the symbolic link referred to by dirfd (which should have been obtained using open(2) with the O_PATH and O_NOFOLLOW flags).

proot doesn't handle this case, and I'm not sure if simply making detranslate_path ignore an empty t_referrer is correct. In fact, I'm not sure if proot's readlinkat handling is otherwise correct at all.

[ruanformigoni]

Hi, I'm also experiencing this issue:

proot: ./path/path.c:547: compare_paths2: Assertion `length2 > 0' failed.

This makes pacman fail in arch. It also makes wine GUI fail when running inside the new root.

Edit: The changes provided by @0pq76r fix both issues.

[alexhenrie]

I am having the same problem. Here is a Dockerfile that reproduces it:

FROM ubuntu:mantic

RUN apt-get update && apt-get install -y proot systemd

RUN proot dpkg-reconfigure systemd

docker build . fails with the message:

0.402 proot: ./path/path.c:541: compare_paths2: Assertion `length2 > 0' failed.

Is there a workaround?