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migration: Ensure vmstate_save() sets errp

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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>
This commit is contained in:
Hanna Czenczek 2024-10-15 19:04:37 +02:00 committed by Peter Xu
parent e620b1e477
commit 37dfcba1a0
1 changed files with 8 additions and 5 deletions
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13
migration/vmstate.c
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@ -22,7 +22,8 @@
#include "trace.h"
static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
void *opaque, JSONWriter *vmdesc);
void *opaque, JSONWriter *vmdesc,
Error **errp);
static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
void *opaque);
@ -441,12 +442,13 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
json_writer_end_array(vmdesc);
}
ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc);
ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp);
if (vmsd->post_save) {
int ps_ret = vmsd->post_save(opaque);
if (!ret) {
if (!ret && ps_ret) {
ret = ps_ret;
error_setg(errp, "post-save failed: %s", vmsd->name);
}
}
return ret;
@ -518,7 +520,8 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
}
static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
void *opaque, JSONWriter *vmdesc)
void *opaque, JSONWriter *vmdesc,
Error **errp)
{
const VMStateDescription * const *sub = vmsd->subsections;
bool vmdesc_has_subsections = false;
@ -546,7 +549,7 @@ static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
qemu_put_byte(f, len);
qemu_put_buffer(f, (uint8_t *)vmsdsub->name, len);
qemu_put_be32(f, vmsdsub->version_id);
ret = vmstate_save_state(f, vmsdsub, opaque, vmdesc);
ret = vmstate_save_state_with_err(f, vmsdsub, opaque, vmdesc, errp);
if (ret) {
return ret;
}