Alexandr Moshkov <[email protected]> writes: > When loading a subset, its name is checked for the parent prefix. The > following bug may occur here: > > Let's say there is a vmstate named "virtio-blk", it has a subsection > named "virtio-blk/subsection", and it also has another vmstate named > "virtio" in the fields. > Then, during the migration, when trying to load this subsection for > "virtio", the prefix condition will pass for "virtio-blk/subsection" and > then the migration will break, because this vmstate does not have such a > subsection. > > In other words, if a field inside vmstate1 is set via vmstate2 with a > name that is a prefix of the parent vmstate, then the field can "steal" > a subsection belonging to the parent state. > > Looks like it happens because migration stream for "virtio-blk" looks > like this: > > [virtio-blk header] [virtio-blk fields] [virtio-blk subsections] > > "virtio-blk" contains "virtio" field, so migration stream is: > > [virtio-blk header] [virtio header] [virtio fields] [virtio > subsections] [virtio-blk subsections] > > And when we load the subsections of the "virtio" device, > vmstate_subsection_load() uses qemu_peek_byte() to try to figure out if > this is his subsection. This is where we encounter an error. > > Thus, the error occurs due to the fact that vmsd does not know how many > subsections it has when loading (this does not appear anywhere in the > migration stream), so it tries to load all the appropriate ones by > names. > > Fix it by checking `/` at the end of idstr. > > Signed-off-by: Alexandr Moshkov <[email protected]> > --- > migration/vmstate.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/migration/vmstate.c b/migration/vmstate.c > index 4d28364f7b..187f3861f2 100644 > --- a/migration/vmstate.c > +++ b/migration/vmstate.c > @@ -613,7 +613,7 @@ static int vmstate_subsection_load(QEMUFile *f, const > VMStateDescription *vmsd, > > while (qemu_peek_byte(f, 0) == QEMU_VM_SUBSECTION) { > char idstr[256], *idstr_ret; > - int ret; > + int ret, vmsd_name_len; > uint8_t version_id, len, size; > const VMStateDescription *sub_vmsd; > > @@ -631,7 +631,10 @@ static int vmstate_subsection_load(QEMUFile *f, const > VMStateDescription *vmsd, > memcpy(idstr, idstr_ret, size); > idstr[size] = 0; > > - if (strncmp(vmsd->name, idstr, strlen(vmsd->name)) != 0) { > + vmsd_name_len = strlen(vmsd->name); > + if (strncmp(vmsd->name, idstr, vmsd_name_len) != 0 || > + /* to avoid taking parent subsection here */ > + idstr[vmsd_name_len] != '/') { > trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(prefix)"); > /* it doesn't have a valid subsection name */ > return 0;
Hi, this breaks migration for s390x and ppc64: qemu-system-s390x: Missing section footer for qemu-s390-flic qemu-system-ppc64: Missing section footer for spapr_iommu
