CVE-2026-98039bpf: Require MEM_PERCPU for percpu kptr stores

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: Require MEM_PERCPU for percpu kptr stores map_kptr_match_type() treats perm_flags as the set of register type flags that a kptr field permits. Adding MEM_PERCPU to that set for BPF_KPTR_PERCPU does not require the source register to carry it, however. The subset test consequently accepts both a plain bpf_obj_new() allocation and a referenced kernel pointer into a __percpu_kptr map field. Loads from the field are always marked MEM_PERCPU. Consumers then treat the stored value as the cookie returned by bpf_percpu_obj_new(): per-CPU pointer helpers relocate it, and map teardown selects the per-CPU free path. A plain allocation can therefore provide an arbitrary kernel read/write, while a kernel pointer can be relocated into an invalid address or sent through a missing destructor. Require the source MEM_PERCPU flag to match the destination field kind. This preserves valid bpf_percpu_obj_new() stores and rejects both the program-BTF and kernel-BTF variants.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/aaa9cf7707d1c5c0d2ca9d40c8b71652ac1c3c3f
• https://git.kernel.org/stable/c/0bdd6121c8dd5f1764efe701ce26bb8e15acb172
• https://git.kernel.org/stable/c/ad4ebae5dbc2d47b544aa54f03c12490065be08a
• https://git.kernel.org/stable/c/048029ba1c793f8cabc4ad5eea765da01903f8f1