tree dd79d22868258d566bcc7e397e800e3067aba19b
parent e620b1e4770bc779a6a9467ff753e0acdd4c57f5
author Hanna Czenczek <hreitz@redhat.com> 1729011877 +0200
committer Peter Xu <peterx@redhat.com> 1730404098 -0400

migration: Ensure vmstate_save() sets errp

migration/savevm.c contains some calls to vmstate_save() that are
followed by migrate_set_error() if the integer return value indicates an
error.  migrate_set_error() requires that the `Error *` object passed to
it is set.  Therefore, vmstate_save() is assumed to always set *errp on
error.

Right now, that assumption is not met: vmstate_save_state_v() (called
internally by vmstate_save()) will not set *errp if
vmstate_subsection_save() or vmsd->post_save() fail.  Fix that by adding
an *errp parameter to vmstate_subsection_save(), and by generating a
generic error in case post_save() fails (as is already done for
pre_save()).

Without this patch, qemu will crash after vmstate_subsection_save() or
post_save() have failed inside of a vmstate_save() call (unless
migrate_set_error() then happen to discard the new error because
s->error is already set).  This happens e.g. when receiving the state
from a virtio-fs back-end (virtiofsd) fails.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Link: https://lore.kernel.org/r/20241015170437.310358-1-hreitz@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>