An issue was discovered in Xen 4.5.x through 4.9.x. The function
`__gnttab_cache_flush` handles GNTTABOP_cache_flush grant table operations.
It checks to see if the calling domain is the owner of the page that is to
be operated on. If it is not, the owner's grant table is checked to see if
a grant mapping to the calling domain exists for the page in question.
However, the function does not check to see if the owning domain actually
has a grant table or not. Some special domains, such as `DOMID_XEN`,
`DOMID_IO` and `DOMID_COW` are created without grant tables. Hence, if
__gnttab_cache_flush operates on a page owned by these special domains, it
will attempt to dereference a NULL pointer in the domain struct.
Source: xen (LP Ubuntu Debian)
Ubuntu 12.04 ESM (Precise Pangolin):DNE
Ubuntu 14.04 ESM (Trusty Tahr):DNE (trusty was not-affected)
Ubuntu 16.04 LTS (Xenial Xerus):released (4.6.5-0ubuntu1.4)
Binaries built from this source package are in universe and so are supported by the community. For more details see
More Information

Updated: 2020-09-10 05:37:21 UTC (commit 81a23a978c4436cd99e1d040e9e73e9146876281)