CVE-2026-98064

Summary

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix NULL-ptr-deref when showing a void BTF type

btf_modifier_show() resolves the modifier and then calls btf_type_ops(t)->show() unconditionally. For the void type (type_id 0, BTF_KIND_UNKN) kind_ops[] has no entry, so ->show is NULL.

A "const void" (a modifier resolving to void) cannot be a map key or value - map_check_btf() rejects it because void has no size - so the map dump path does not reach it. But bpf_snprintf_btf() takes a type_id straight from the BPF program, and passing such a "const void" from the vmlinux BTF NULL-derefs:

KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] RIP: 0010:btf_modifier_show (kernel/bpf/btf.c:2914) Call Trace: <TASK> btf_type_show (kernel/bpf/btf.c:8251) btf_type_snprintf_show (kernel/bpf/btf.c:8321) bpf_snprintf_btf (kernel/trace/bpf_trace.c:1047) bpf_prog_test_run_raw_tp (net/bpf/test_run.c:829) __sys_bpf (kernel/bpf/syscall.c:4804) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) </TASK>

Fall back to btf_df_show() when the resolved type has no show op; it emits the "<unsupported kind:N>" placeholder already used for kinds like FWD and FUNC. bpf_snprintf_btf() then returns the length as usual.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/717abdfd1d559d01fdd102023f0a990fb0437240
• https://git.kernel.org/stable/c/98f1cb95221332139acf514350ae2cae3b8656c5
• https://git.kernel.org/stable/c/5324f4e75ff6e9c2ca2e267c5f34f0937f9d0ac9
• https://git.kernel.org/stable/c/4ea508b9ebd78bce7f212166d2e2cba66b875f08

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