Xen Security Advisory CVE-2021-28038 / XSA-367
Linux: netback fails to honor grant mapping errors
UPDATES IN VERSION 2
XSA-362 tried to address issues here, but in the case of the netback
driver the changes were insufficient: It left the relevant function
invocation with, effectively, no error handling at all. As a result,
memory allocation failures there could still lead to frontend-induced
crashes of the backend.
A malicious or buggy networking frontend driver may be able to crash
the corresponding backend driver, potentially affecting the entire
domain running the backend driver. In a typical (non-disaggregated)
system that is a host-wide denial of service (DoS).
Linux versions from at least 2.6.39 onwards are vulnerable, when run in
PV mode. Earlier versions differ significantly in behavior and may
therefore instead surface other issues under the same conditions. Linux
run in HVM / PVH modes is not vulnerable.
For Linux, running the backends in HVM or PVH domains will avoid the
vulnerability. For example, by running the dom0 in PVH mode.
In all other cases there is no known mitigation.
Applying the attached patch resolves this issue.
xsa367-linux.patch Linux 5.12-rc
$ sha256sum xsa367*
This issue was reported by Intel's kernel test robot and recognized as a
security issue by Jan Beulich of SUSE.
NOTE REGARDING LACK OF EMBARGO
This issue was reported publicly, before the XSA could be issued.
Created xen tracking bugs for this issue:
Affects: fedora-all [bug 1936567]
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.
This was fixed for Fedora with the 5.10.21 stable kernel update.