Re: [libvirt] [PATCH 2/5] qemu: Avoid using stale data in virDomainGetBlockInfo

On 01/07/2014 07:22 AM, Jiri Denemark wrote: > On Tue, Dec 24, 2013 at 07:22:38 -0700, Eric Blake wrote: >> On 12/20/2013 02:36 PM, Jiri Denemark wrote: >>> Generally, every API that is going to begin a job should do that before >>> fetching data from vm->def. However, qemuDomainGetBlockInfo does not >>> know whether it will have to start a job or not before checking vm->def. >>> To avoid using disk alias that might have been freed while we were >>> waiting for a job, we use its copy. In case the disk was removed in the >>> meantime, we will fail with "cannot find statistics for device '...'" >>> error message. >>> >>> Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; >>> --- >>> src/qemu/qemu_driver.c | 17 ++++++++++++----- >>> 1 file changed, 12 insertions(+), 5 deletions(-) >> >> This fixes the potential for a crash, but isn't this related to the same >> problem that John has been working on? That is, when one thread is >> migrating a domain and the other is getting block info, we have a race >> where qemu will quit before we get a chance to probe for the block info. >> https://www.redhat.com/archives/libvir-list/2013-December/msg00984.html >> >> Would changing when we grab the job (and grabbing it unconditionally, >> even if we end up not needing to query) help solve both issues? > > I might help with what John was trying to do but I don't think this > patch alone would solve the issue. May I consider this patch ACKed? :-) I was debating whether a single patch could solve both issues at once, to avoid rebase churn; but at this point, given that it solves a CVE, I'm okay giving ACK to your patch as-is.