CVE-2026-23102

When SME is supported, Restoring SVE signal context can go wrong in a few ways, including placing the task into an invalid state where the kernel may read from out-of-bounds memory (and may potentially take a fatal fault) and/or may kill the task with a SIGKILL.

(1) Restoring a context with SVESIGFLAGSM set can place the task into an invalid state where SVCR.SM is set (and svestate is non-NULL) but TIF_SME is clear, consequently resuting in out-of-bounds memory reads and/or killing the task with SIGKILL.

This can only occur in unusual (but legitimate) cases where the SVE
signal context has either been modified by userspace or was saved in
the context of another task (e.g. as with CRIU), as otherwise the
presence of an SVE signal context with SVE_SIG_FLAG_SM implies that
TIF_SME is already set.

While in this state, task_fpsimd_load() will NOT configure SMCR_ELx
(leaving some arbitrary value configured in hardware) before
restoring SVCR and attempting to restore the streaming mode SVE
registers from memory via sve_load_state(). As the value of
SMCR_ELx.LEN may be larger than the task's streaming SVE vector
length, this may read memory outside of the task's allocated
sve_state, reading unrelated data and/or triggering a fault.

While this can result in secrets being loaded into streaming SVE
registers, these values are never exposed. As TIF_SME is clear,
fpsimd_bind_task_to_cpu() will configure CPACR_ELx.SMEN to trap EL0
accesses to streaming mode SVE registers, so these cannot be
accessed directly at EL0. As fpsimd_save_user_state() verifies the
live vector length before saving (S)SVE state to memory, no secret
values can be saved back to memory (and hence cannot be observed via
ptrace, signals, etc).

When the live vector length doesn't match the expected vector length
for the task, fpsimd_save_user_state() will send a fatal SIGKILL
signal to the task. Hence the task may be killed after executing
userspace for some period of time.

(2) Restoring a context with SVESIGFLAG_SM clear does not clear the task's SVCR.SM. If SVCR.SM was set prior to restoring the context, then the task will be left in streaming mode unexpectedly, and some register state will be combined inconsistently, though the task will be left in legitimate state from the kernel's PoV.

This can only occur in unusual (but legitimate) cases where ptrace
has been used to set SVCR.SM after entry to the sigreturn syscall,
as syscall entry clears SVCR.SM.

In these cases, the the provided SVE register data will be loaded
into the task's sve_state using the non-streaming SVE vector length
and the FPSIMD registers will be merged into this using the
streaming SVE vector length.

Fix (1) by setting TIFSME when setting SVCR.SM. This also requires ensuring that the task's smestate has been allocated, but as this could contain live ZA state, it should not be zeroed. Fix (2) by clearing SVCR.SM when restoring a SVE signal context with SVESIGFLAG_SM clear.

For consistency, I've pulled the manipulation of SVCR, TIFSVE, TIFSME, and fptype earlier, immediately after the allocation of svestate/sme_state, before the restore of the actual register state. This makes it easier to ensure that these are always modified consistently, even if a fault is taken while reading the register data from the signal context. I do not expect any software to depend on the exact state restored when a fault is taken while reading the context.

Database specific

{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23102.json",
    "cna_assigner": "Linux"
}

References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type: GIT
Repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events: Introduced

85ed24dad2904f7c141911d91b7807ab02694b5e

Fixed

9bc3adba8c35119be80ab20217027720446742f2

Fixed

ce820dd4e6e2d711242dc4331713b9bb4fe06d09

Fixed

7b5a52cf252a0d2e89787b645290ad288878f332

Fixed

d2907cbe9ea0a54cbe078076f9d089240ee1e2d9

Affected versions

v5.*

v5.18

v5.18-rc4

v5.18-rc5

v5.18-rc6

v5.18-rc7

v5.19

v5.19-rc1

v5.19-rc2

v5.19-rc3

v5.19-rc4

v5.19-rc5

v5.19-rc6

v5.19-rc7

v5.19-rc8

v6.*

v6.0

v6.0-rc1

v6.0-rc2

v6.0-rc3

v6.0-rc4

v6.0-rc5

v6.0-rc6

v6.0-rc7

v6.1

v6.1-rc1

v6.1-rc2

v6.1-rc3

v6.1-rc4

v6.1-rc5

v6.1-rc6

v6.1-rc7

v6.1-rc8

v6.1.1

v6.1.10

v6.1.100

v6.1.101

v6.1.102

v6.1.103

v6.1.104

v6.1.105

v6.1.106

v6.1.107

v6.1.108

v6.1.109

v6.1.11

v6.1.110

v6.1.111

v6.1.112

v6.1.113

v6.1.114

v6.1.115

v6.1.116

v6.1.117

v6.1.118

v6.1.119

v6.1.12

v6.1.120

v6.1.121

v6.1.122

v6.1.123

v6.1.124

v6.1.125

v6.1.126

v6.1.127

v6.1.128

v6.1.129

v6.1.13

v6.1.130

v6.1.131

v6.1.132

v6.1.133

v6.1.134

v6.1.135

v6.1.136

v6.1.137

v6.1.138

v6.1.139

v6.1.14

v6.1.140

v6.1.141

v6.1.142

v6.1.143

v6.1.144

v6.1.145

v6.1.146

v6.1.147

v6.1.148

v6.1.149

v6.1.15

v6.1.150

v6.1.151

v6.1.152

v6.1.153

v6.1.154

v6.1.155

v6.1.156

v6.1.157

v6.1.158

v6.1.159

v6.1.16

v6.1.160

v6.1.161

v6.1.17

v6.1.18

v6.1.19

v6.1.2

v6.1.20

v6.1.21

v6.1.22

v6.1.23

v6.1.24

v6.1.25

v6.1.26

v6.1.27

v6.1.28

v6.1.29

v6.1.3

v6.1.30

v6.1.31

v6.1.32

v6.1.33

v6.1.34

v6.1.35

v6.1.36

v6.1.37

v6.1.38

v6.1.39

v6.1.4

v6.1.40

v6.1.41

v6.1.42

v6.1.43

v6.1.44

v6.1.45

v6.1.46

v6.1.47

v6.1.48

v6.1.49

v6.1.5

v6.1.50

v6.1.51

v6.1.52

v6.1.53

v6.1.54

v6.1.55

v6.1.56

v6.1.57

v6.1.58

v6.1.59

v6.1.6

v6.1.60

v6.1.61

v6.1.62

v6.1.63

v6.1.64

v6.1.65

v6.1.66

v6.1.67

v6.1.68

v6.1.69

v6.1.7

v6.1.70

v6.1.71

v6.1.72

v6.1.73

v6.1.74

v6.1.75

v6.1.76

v6.1.77

v6.1.78

v6.1.79

v6.1.8

v6.1.80

v6.1.81

v6.1.82

v6.1.83

v6.1.84

v6.1.85

v6.1.86

v6.1.87

v6.1.88

v6.1.89

v6.1.9

v6.1.90

v6.1.91

v6.1.92

v6.1.93

v6.1.94

v6.1.95

v6.1.96

v6.1.97

v6.1.98

v6.1.99

v6.10

v6.10-rc1

v6.10-rc2

v6.10-rc3

v6.10-rc4

v6.10-rc5

v6.10-rc6

v6.10-rc7

v6.11

v6.11-rc1

v6.11-rc2

v6.11-rc3

v6.11-rc4

v6.11-rc5

v6.11-rc6

v6.11-rc7

v6.12

v6.12-rc1

v6.12-rc2

v6.12-rc3

v6.12-rc4

v6.12-rc5

v6.12-rc6

v6.12-rc7

v6.13

v6.13-rc1

v6.13-rc2

v6.13-rc3

v6.13-rc4

v6.13-rc5

v6.13-rc6

v6.13-rc7

v6.14

v6.14-rc1

v6.14-rc2

v6.14-rc3

v6.14-rc4

v6.14-rc5

v6.14-rc6

v6.14-rc7

v6.15

v6.15-rc1

v6.15-rc2

v6.15-rc3

v6.15-rc4

v6.15-rc5

v6.15-rc6

v6.15-rc7

v6.16

v6.16-rc1

v6.16-rc2

v6.16-rc3

v6.16-rc4

v6.16-rc5

v6.16-rc6

v6.16-rc7

v6.17

v6.17-rc1

v6.17-rc2

v6.17-rc3

v6.17-rc4

v6.17-rc5

v6.17-rc6

v6.17-rc7

v6.18

v6.18-rc1

v6.18-rc2

v6.18-rc3

v6.18-rc4

v6.18-rc5

v6.18-rc6

v6.18-rc7

v6.18.1

v6.18.2

v6.18.3

v6.18.4

v6.18.5

v6.18.6

v6.18.7

v6.19-rc1

v6.2

v6.2-rc1

v6.2-rc2

v6.2-rc3

v6.2-rc4

v6.2-rc5

v6.2-rc6

v6.2-rc7

v6.2-rc8

v6.3

v6.3-rc1

v6.3-rc2

v6.3-rc3

v6.3-rc4

v6.3-rc5

v6.3-rc6

v6.3-rc7

v6.4

v6.4-rc1

v6.4-rc2

v6.4-rc3

v6.4-rc4

v6.4-rc5

v6.4-rc6

v6.4-rc7

v6.5

v6.5-rc1

v6.5-rc2

v6.5-rc3

v6.5-rc4

v6.5-rc5

v6.5-rc6

v6.5-rc7

v6.6

v6.6-rc1

v6.6-rc2

v6.6-rc3

v6.6-rc4

v6.6-rc5

v6.6-rc6

v6.6-rc7

v6.6.1

v6.6.10

v6.6.100

v6.6.101

v6.6.102

v6.6.103

v6.6.104

v6.6.105

v6.6.106

v6.6.107

v6.6.108

v6.6.109

v6.6.11

v6.6.110

v6.6.111

v6.6.112

v6.6.113

v6.6.114

v6.6.115

v6.6.116

v6.6.117

v6.6.118

v6.6.119

v6.6.12

v6.6.120

v6.6.121

v6.6.122

v6.6.13

v6.6.14

v6.6.15

v6.6.16

v6.6.17

v6.6.18

v6.6.19

v6.6.2

v6.6.20

v6.6.21

v6.6.22

v6.6.23

v6.6.24

v6.6.25

v6.6.26

v6.6.27

v6.6.28

v6.6.29

v6.6.3

v6.6.30

v6.6.31

v6.6.32

v6.6.33

v6.6.34

v6.6.35

v6.6.36

v6.6.37

v6.6.38

v6.6.39

v6.6.4

v6.6.40

v6.6.41

v6.6.42

v6.6.43

v6.6.44

v6.6.45

v6.6.46

v6.6.47

v6.6.48

v6.6.49

v6.6.5

v6.6.50

v6.6.51

v6.6.52

v6.6.53

v6.6.54

v6.6.55

v6.6.56

v6.6.57

v6.6.58

v6.6.59

v6.6.6

v6.6.60

v6.6.61

v6.6.62

v6.6.63

v6.6.64

v6.6.65

v6.6.66

v6.6.67

v6.6.68

v6.6.69

v6.6.7

v6.6.70

v6.6.71

v6.6.72

v6.6.73

v6.6.74

v6.6.75

v6.6.76

v6.6.77

v6.6.78

v6.6.79

v6.6.8

v6.6.80

v6.6.81

v6.6.82

v6.6.83

v6.6.84

v6.6.85

v6.6.86

v6.6.87

v6.6.88

v6.6.89

v6.6.9

v6.6.90

v6.6.91

v6.6.92

v6.6.93

v6.6.94

v6.6.95

v6.6.96

v6.6.97

v6.6.98

v6.6.99

v6.7

v6.7-rc1

v6.7-rc2

v6.7-rc3

v6.7-rc4

v6.7-rc5

v6.7-rc6

v6.7-rc7

v6.7-rc8

v6.8

v6.8-rc1

v6.8-rc2

v6.8-rc3

v6.8-rc4

v6.8-rc5

v6.8-rc6

v6.8-rc7

v6.9

v6.9-rc1

v6.9-rc2

v6.9-rc3

v6.9-rc4

v6.9-rc5

v6.9-rc6

v6.9-rc7

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-23102.json"

Linux / Kernel

Package

Name: Kernel

Affected ranges

Type: ECOSYSTEM
Events: Introduced

5.19.0

Fixed

6.1.162

Type: ECOSYSTEM
Events: Introduced

6.2.0

Fixed

6.6.123

Type: ECOSYSTEM
Events: Introduced

6.7.0

Fixed

6.18.8

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-23102.json"