bpf: Fix BPF_F_CPU validation for sparse CPU IDs
BPF_F_CPU stores the target CPU ID in the upper 32 bits of the map
operation flags. bpf_map_check_op_flags() currently compares that ID
with num_possible_cpus(), which is the number of possible CPUs rather
than a bound on CPU IDs.
On an arm64 QEMU guest with a CPU device-tree hole, the possible CPU
mask was 0,2-3. A userspace program using raw bpf() syscalls creates
a BPF_MAP_TYPE_PERCPU_ARRAY and performs update and lookup operations
for each CPU by setting BPF_F_CPU and the CPU ID in the flags.
With the old check, CPU 1 is incorrectly accepted while valid CPU 3 is
rejected with -ERANGE. The CPU 1 update then reaches the per-CPU map
access path and triggers:
Unable to handle kernel paging request at virtual address ...
pc : __pi_memcpy_generic+0x5c/0x22c
lr : bpf_percpu_array_update+0x2dc/0x2e8
Call trace:
__pi_memcpy_generic
bpf_map_update_value
map_update_elem
__sys_bpf
Check the CPU ID against nr_cpu_ids and cpu_possible() instead. This
rejects CPU IDs outside the valid range and CPUs absent from the
possible mask, while allowing valid sparse CPU IDs.
Analysis
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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 |
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| Linux | Linux | affected |
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No vendor fix or workaround currently provided.
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Fri, 25 Sep 2026 12:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-190 CWE-404 |
Fri, 25 Sep 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: Fix BPF_F_CPU validation for sparse CPU IDs BPF_F_CPU stores the target CPU ID in the upper 32 bits of the map operation flags. bpf_map_check_op_flags() currently compares that ID with num_possible_cpus(), which is the number of possible CPUs rather than a bound on CPU IDs. On an arm64 QEMU guest with a CPU device-tree hole, the possible CPU mask was 0,2-3. A userspace program using raw bpf() syscalls creates a BPF_MAP_TYPE_PERCPU_ARRAY and performs update and lookup operations for each CPU by setting BPF_F_CPU and the CPU ID in the flags. With the old check, CPU 1 is incorrectly accepted while valid CPU 3 is rejected with -ERANGE. The CPU 1 update then reaches the per-CPU map access path and triggers: Unable to handle kernel paging request at virtual address ... pc : __pi_memcpy_generic+0x5c/0x22c lr : bpf_percpu_array_update+0x2dc/0x2e8 Call trace: __pi_memcpy_generic bpf_map_update_value map_update_elem __sys_bpf Check the CPU ID against nr_cpu_ids and cpu_possible() instead. This rejects CPU IDs outside the valid range and CPUs absent from the possible mask, while allowing valid sparse CPU IDs. | |
| Title | bpf: Fix BPF_F_CPU validation for sparse CPU IDs | |
| 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: 2026-09-25T10:36:22.774Z
Reserved: 2026-09-25T10:25:14.320Z
Link: CVE-2026-98150
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:46.580
Modified: 2026-09-25T11:17:46.580
Link: CVE-2026-98150
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-25T12:15:16Z