Information

Advisory

XSA-367

Public release

2021-03-04 10:39

Updated

2021-03-05 17:07

Version

2

CVE(s)

CVE-2021-28038

Title

Linux: netback fails to honor grant mapping errors

Filesadvisory-367.txt (signed advisory file)
xsa367-linux.patchAdvisory

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256

        Xen Security Advisory CVE-2021-28038 / XSA-367
                          version 2

      Linux: netback fails to honor grant mapping errors

UPDATES IN VERSION 2

CVE assigned.

ISSUE DESCRIPTION

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.

IMPACT

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).

VULNERABLE SYSTEMS

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.

MITIGATION

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.

RESOLUTION

Applying the attached patch resolves this issue.

xsa367-linux.patch Linux 5.12-rc

$ sha256sum xsa367* b0244bfddee91cd7986172893e70664b74e698c5d44f25865870f179f80f9a92 xsa367-linux.patch $

CREDITS

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. -----BEGIN PGP SIGNATURE-----

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Xenproject.org Security Team