CVE-2026-98063

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

bpf: Fix NULL-ptr-deref in btf_var_show()

btf_var_show() calls btf_type_id_resolve() unconditionally, which

dereferences btf->resolved_ids. That is NULL for a base BTF - e.g. the

vmlinux BTF that bpf_snprintf_btf() renders against - since base BTF is

not resolved during parsing. btf_modifier_show() guards this with

'if (btf->resolved_ids)', but btf_var_show() does not.

A BPF program that passes the type_id of a BTF_KIND_VAR from the vmlinux

BTF to bpf_snprintf_btf() thus NULL-derefs:

KASAN: probably user-memory-access in range [0x46638-0x4663f]

RIP: 0010:btf_var_show (kernel/bpf/btf.c:2929)

Call Trace:

<TASK>

btf_type_show (kernel/bpf/btf.c:8259)

btf_type_snprintf_show (kernel/bpf/btf.c:8329)

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:84)

entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

</TASK>

Resolve the var's type directly with btf_type_skip_modifiers() when

resolved_ids is NULL, mirroring btf_modifier_show().