[pve-devel] [PATCH common] tools: unbless errors in run_fork_with_timeout

[Wolfgang Bumiller]

We cannot properly encode blessed objects as json, so
instead, we should stringify them. This happened for
instance if a VM's systemd scope wasn't cleaned up as we
got an error as a Net::DBus::Error object causing a
"malformed json string" error to appear instead of the
actual message.

Additionally, add a 'must_stringify' helper: The above error
object implements a '""' operator for stringification (as
all error sshould), but in theory that could die as well, in
which case we just return a generic error string we'll
hopefully never see...

Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
---
 src/PVE/Tools.pm | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/PVE/Tools.pm b/src/PVE/Tools.pm
index 1c5b502..53ac83f 100644
--- a/src/PVE/Tools.pm
+++ b/src/PVE/Tools.pm
@@ -904,6 +904,13 @@ sub next_spice_port {
     return next_unused_port(61000, 61099, $family, $address);
 }
 
+sub must_stringify {
+	my ($value) = @_;
+	eval { $value = "$value" };
+	return "error turning value into a string: $@" if $@;
+	return $value;
+}
+
 # sigkill after $timeout  a $sub running in a fork if it can't write a pipe
 # the $sub has to return a single scalar
 sub run_fork_with_timeout {
@@ -935,7 +942,7 @@ sub run_fork_with_timeout {
 	    $pipe_out->flush();
 	};
 	if (my $err = $@) {
-	    print {$pipe_out} encode_json({ error => $err });
+	    print {$pipe_out} encode_json({ error => must_stringify($err) });
 	    $pipe_out->flush();
 	    POSIX::_exit(1);
 	}
-- 
2.11.0