About vulnerability

In the Linux kernel, the following vulnerability has been resolved:

smack: /smack/doi: accept previously used values

Writing to /smack/doi a value that has ever been written there in the past disables networking for non-ambient labels. E.g.

cat /smack/doi

3

netlabelctl -p cipso list

Configured CIPSO mappings (1) DOI value : 3 mapping type : PASS_THROUGH

netlabelctl -p map list

Configured NetLabel domain mappings (3) domain: “_” (IPv4) protocol: UNLABELED domain: DEFAULT (IPv4) protocol: CIPSO, DOI = 3 domain: DEFAULT (IPv6) protocol: UNLABELED

cat /smack/ambient

_

cat /proc/$$/attr/smack/current

_

ping -c1 10.1.95.12

64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.964 ms

echo foo >/proc/$$/attr/smack/current

ping -c1 10.1.95.12

64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.956 ms unknown option 86

echo 4 >/smack/doi

echo 3 >/smack/doi

!> [ 214.050395] smk_cipso_doi:691 cipso add rc = -17

echo 3 >/smack/doi

!> [ 249.402261] smk_cipso_doi:678 remove rc = -2 !> [ 249.402261] smk_cipso_doi:691 cipso add rc = -17

ping -c1 10.1.95.12

!!> ping: 10.1.95.12: Address family for hostname not supported

echo _ >/proc/$$/attr/smack/current

ping -c1 10.1.95.12

64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.617 ms

This happens because Smack keeps decommissioned DOIs, fails to re-add them, and consequently refuses to add the “default” domain map:

netlabelctl -p cipso list

Configured CIPSO mappings (2) DOI value : 3 mapping type : PASS_THROUGH DOI value : 4 mapping type : PASS_THROUGH

netlabelctl -p map list

Configured NetLabel domain mappings (2) domain: “_” (IPv4) protocol: UNLABELED !> (no ipv4 map for default domain here) domain: DEFAULT (IPv6) protocol: UNLABELED

Fix by clearing decommissioned DOI definitions and serializing concurrent DOI updates with a new lock.

Also:

• allow /smack/doi to live unconfigured, since adding a map (netlbl_cfg_cipsov4_map_add) may fail. CIPSO_V4_DOI_UNKNOWN(0) indicates the unconfigured DOI
• add new DOI before removing the old default map, so the old map remains if the add fails

(2008-02-04, Casey Schaufler)

Affected product:

AlmaLinux 9.2 ESU , Amazon Linux 2 ELS , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Debian 10 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS

Affected packages:

kernel @ 5.10.0 (+18 more)

Live-patch status from KernelCare for each operating system.