Linux Kernel BPF F_CPU CPU ID Validation Flaw
CVE-2026-98150 Published on September 25, 2026
bpf: Fix BPF_F_CPU validation for sparse CPU IDs
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.
Products Associated with CVE-2026-98150
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Affected Versions
Linux:- Version 2b421662c7887a0649fe409155a1f101562d0fa9 and below bdc5941f6eeef90b76a07fd8ca38ac1933ba2195 is affected.
- Version 2b421662c7887a0649fe409155a1f101562d0fa9 and below ed54bf564ac52699cf4def3d0c2125d493e756f9 is affected.
- Version 7.0 is affected.
- Before 7.0 is unaffected.
- Version 7.2.7, <= 7.2.* is unaffected.
- Version 7.3-rc2, <= * is unaffected.