1 ==================================
2 Register File Data Sampling (RFDS)
3 ==================================
4
5 Register File Data Sampling (RFDS) is a microa
6 only affects Intel Atom parts(also branded as
7 a malicious actor to infer data values previou
8 registers, vector registers, or integer regist
9 ability to choose which data is inferred. CVE-
10
11 Affected Processors
12 ===================
13 Below is the list of affected Intel processors
14
15 =================== ============
16 Common name Family_Model
17 =================== ============
18 ATOM_GOLDMONT 06_5CH
19 ATOM_GOLDMONT_D 06_5FH
20 ATOM_GOLDMONT_PLUS 06_7AH
21 ATOM_TREMONT_D 06_86H
22 ATOM_TREMONT 06_96H
23 ALDERLAKE 06_97H
24 ALDERLAKE_L 06_9AH
25 ATOM_TREMONT_L 06_9CH
26 RAPTORLAKE 06_B7H
27 RAPTORLAKE_P 06_BAH
28 ATOM_GRACEMONT 06_BEH
29 RAPTORLAKE_S 06_BFH
30 =================== ============
31
32 As an exception to this table, Intel Xeon E fa
33 RAPTORLAKE(06_B7H) codenamed Catlow are not af
34 vulnerable in Linux because they share the sam
35 part. Unlike their affected counterparts, they
36 CPUID.HYBRID. This information could be used t
37 affected and unaffected parts, but it is deeme
38 the reporting is fixed automatically when thes
39
40 Mitigation
41 ==========
42 Intel released a microcode update that enables
43 information using the VERW instruction. Like M
44 mitigation strategy to force the CPU to clear
45 attacker can extract the secrets. This is achi
46 unused and obsolete VERW instruction in combin
47 The microcode clears the affected CPU buffers
48 executed.
49
50 Mitigation points
51 -----------------
52 VERW is executed by the kernel before returnin
53 before VMentry. None of the affected cores sup
54 at C-state transitions.
55
56 New bits in IA32_ARCH_CAPABILITIES
57 ----------------------------------
58 Newer processors and microcode update on exist
59 bits to IA32_ARCH_CAPABILITIES MSR. These bits
60 vulnerability and mitigation capability:
61
62 - Bit 27 - RFDS_NO - When set, processor is no
63 - Bit 28 - RFDS_CLEAR - When set, processor is
64 microcode that clears the affected buffers o
65
66 Mitigation control on the kernel command line
67 ---------------------------------------------
68 The kernel command line allows to control RFDS
69 parameter "reg_file_data_sampling=". The valid
70
71 ========== ================================
72 on If the CPU is vulnerable, enable
73 on exit to userspace and before
74 off Disables mitigation.
75 ========== ================================
76
77 Mitigation default is selected by CONFIG_MITIG
78
79 Mitigation status information
80 -----------------------------
81 The Linux kernel provides a sysfs interface to
82 vulnerability status of the system: whether th
83 which mitigations are active. The relevant sys
84
85 /sys/devices/system/cpu/vulnerabilitie
86
87 The possible values in this file are:
88
89 .. list-table::
90
91 * - 'Not affected'
92 - The processor is not vulnerable
93 * - 'Vulnerable'
94 - The processor is vulnerable, but no m
95 * - 'Vulnerable: No microcode'
96 - The processor is vulnerable but micro
97 * - 'Mitigation: Clear Register File'
98 - The processor is vulnerable and the C
99 enabled.
100
101 References
102 ----------
103 .. [#f1] Affected Processors
104 https://www.intel.com/content/www/us/en/dev
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