On Tue, Aug 07, 2018 at 03:07:07PM +0200, Thomas Huth wrote: > On 08/07/2018 02:58 PM, Daniel P. Berrangé wrote: > > On Tue, Aug 07, 2018 at 01:52:24PM +0100, Dr. David Alan Gilbert wrote: > >> * Peter Maydell (peter.mayd...@linaro.org) wrote: > >>> The data in an mbuf buffer is not necessarily at the start of the > >>> allocated buffer. (For instance m_adj() allows data to be trimmed > >>> from the start by just advancing the pointer and reducing the length.) > >>> This means that the allocated buffer size (m->m_size) and the > >>> amount of space from the m_data pointer to the end of the > >>> buffer (M_ROOM(m)) are not necessarily the same. > >>> > >>> Commit 864036e251f54c9 tried to change the m_inc() function from > >>> taking the new allocated-buffer-size to taking the new room-size, > >>> but forgot to change the initial "do we already have enough space" > >>> check. This meant that if we were trying to extend a buffer which > >>> had a leading gap between the buffer start and the data, we might > >>> incorrectly decide it didn't need to be extended, and then > >>> overrun the end of the buffer, causing memory corruption and > >>> an eventual crash. > >>> > >>> Change the "already big enough?" condition from checking the > >>> argument against m->m_size to checking against M_ROOM(). > >>> This only makes a difference for the callsite in m_cat(); > >>> the other three callsites all start with a freshly allocated > >>> mbuf from m_get(), which will have m->m_size == M_ROOM(m). > >>> > >>> Fixes: 864036e251f54c9 > > > > IIUC, this changeset was a security fix for CVE-2018-11806. > > > > Given that the fix was flawed and allowed guest to crash the host > > with a new buffer overrun, it seems we need to get a new CVE allocated > > too. > > But 864036e251f54c9 was never part of an official QEMU release, was it? > Or did it go into a stable release already? If not, I think you simply > need both patches to fix the CVE instead.
Ah possibly - I didn't look at where 864036e251f54c9 was actually release or not. If its onyl git master, then yeah, we can use the same CVE we already have. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
