Description
In the Linux kernel, the following vulnerability has been resolved:
bpf, s390: Clear fetch destination on faulting arena atomic
Same missing register clear as on riscv64. A RMW atomic on an arena pointer
is converted to BPF_PROBE_ATOMIC and gets an exception table entry, but
bpf_jit_probe_atomic_pre() only fills in the arena base and the probe
offset, leaving probe->reg at the -1 that bpf_jit_probe_init() set, which
bpf_jit_probe_post() writes into the entry and ex_handler_bpf() then reads
back as "there is nothing to clear".
That is right for a plain BPF_{ADD,AND,OR,XOR}, which only writes memory,
but an RMW carrying BPF_FETCH also reads the old value into a register:
src_reg for BPF_{ADD,AND,OR,XOR} | BPF_FETCH and BPF_XCHG, and r0 for
BPF_CMPXCHG. So on a fault over an unmapped arena page the program resumes
at the landing pad with whatever that register held before the atomic
instead of the 0 that every other BPF_PROBE_* access delivers.
Fill probe->reg in from bpf_atomic_load_reg(). Unlike x86-64 and arm64,
s390x does not report arena violations from its exception handler, so there
is no access direction to correct here, only the missing register clear.
bpf, s390: Clear fetch destination on faulting arena atomic
Same missing register clear as on riscv64. A RMW atomic on an arena pointer
is converted to BPF_PROBE_ATOMIC and gets an exception table entry, but
bpf_jit_probe_atomic_pre() only fills in the arena base and the probe
offset, leaving probe->reg at the -1 that bpf_jit_probe_init() set, which
bpf_jit_probe_post() writes into the entry and ex_handler_bpf() then reads
back as "there is nothing to clear".
That is right for a plain BPF_{ADD,AND,OR,XOR}, which only writes memory,
but an RMW carrying BPF_FETCH also reads the old value into a register:
src_reg for BPF_{ADD,AND,OR,XOR} | BPF_FETCH and BPF_XCHG, and r0 for
BPF_CMPXCHG. So on a fault over an unmapped arena page the program resumes
at the landing pad with whatever that register held before the atomic
instead of the 0 that every other BPF_PROBE_* access delivers.
Fill probe->reg in from bpf_atomic_load_reg(). Unlike x86-64 and arm64,
s390x does not report arena violations from its exception handler, so there
is no access direction to correct here, only the missing register clear.
Published:
2026-09-17
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf, s390: Clear fetch destination on faulting arena atomic Same missing register clear as on riscv64. A RMW atomic on an arena pointer is converted to BPF_PROBE_ATOMIC and gets an exception table entry, but bpf_jit_probe_atomic_pre() only fills in the arena base and the probe offset, leaving probe->reg at the -1 that bpf_jit_probe_init() set, which bpf_jit_probe_post() writes into the entry and ex_handler_bpf() then reads back as "there is nothing to clear". That is right for a plain BPF_{ADD,AND,OR,XOR}, which only writes memory, but an RMW carrying BPF_FETCH also reads the old value into a register: src_reg for BPF_{ADD,AND,OR,XOR} | BPF_FETCH and BPF_XCHG, and r0 for BPF_CMPXCHG. So on a fault over an unmapped arena page the program resumes at the landing pad with whatever that register held before the atomic instead of the 0 that every other BPF_PROBE_* access delivers. Fill probe->reg in from bpf_atomic_load_reg(). Unlike x86-64 and arm64, s390x does not report arena violations from its exception handler, so there is no access direction to correct here, only the missing register clear. | |
| Title | bpf, s390: Clear fetch destination on faulting arena atomic | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:07:25.454Z
Reserved: 2026-09-11T19:38:34.793Z
Link: CVE-2026-90211
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:16.330
Modified: 2026-09-17T17:17:16.330
Link: CVE-2026-90211
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.