Description of problem:

This bug was found by Olaf Hering.

Issuing the 'sh' command before mounting any filesystem will
cause the daemon to segfault.

Version-Release number of selected component (if applicable):

libguestfs 1.20.10
libguestfs 1.22.5
libguestfs 1.23.18

How reproducible:

100%

Steps to Reproduce:

guestfish --ro -v -a /dev/null run : sh "foo" : ls /

Actual results:

You will see in the debug output that guestfsd has segfaulted.
The output will look similar to:

guestfsd: error: do_command: you must call 'mount' first to mount the root filesystem
*** Error in `guestfsd': free(): invalid pointer: 0x00007fffc1c8d560 ***
libguestfs: error: sh: do_command: you must call 'mount' first to mount the root filesystem
/init: line 167:   145 Aborted                 $vg guestfsd
Rebooting.

(The precise message will differ between versions of libguestfs
but it should be obvious that guestfsd has segfaulted)

Expected results:

guestfsd should return an error and not segfault.

Additional info: