CVE-2026-98064bpf: Fix NULL-ptr-deref when showing a void BTF type

Official description

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 packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/cf528f2d7a0a54f2a3c6d439cfa3c8d7dfe90d8d
• https://git.kernel.org/stable/c/adb15557a641cb8a31f83e5f62bd12042b138c7b
• https://git.kernel.org/stable/c/62b00074b58ccf43f61f70f2cfcac80937b530c6
• https://git.kernel.org/stable/c/86d86f9fcf62dd3654090fbf3cf7ae5f42aa0706
• 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