On 15.10.24 18:06, Peter Xu wrote:
On Tue, Oct 15, 2024 at 04:15:15PM +0200, Hanna Czenczek wrote:
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 <hre...@redhat.com>
---
migration/vmstate.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/migration/vmstate.c b/migration/vmstate.c
index ff5d589a6d..13532f2807 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -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) {
Perhaps here it needs to be "if (!ret && ps_ret)" now, otherwise the error
will be attached even if no error for both retvals?
Not just perhaps, that seems kind of vital indeed...
(I blame my brain’s less-than-stellar pattern matching that might have
interpreted this as the error path *cough*)
Other than that it looks good.
Thanks for the quick review! Will respin.
Hanna
Thanks,
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;
}
--
2.45.2
