In the Linux kernel, the following vulnerability has been resolved: bpf: Reject programs with inlined helpers if JIT is not available When an architecture (such as LoongArch, ARM64, and RISC-V) implements bpf_jit_inlines_helper_call(),…

Overview

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

bpf: Reject programs with inlined helpers if JIT is not available

When an architecture (such as LoongArch, ARM64, and RISC-V) implements bpf_jit_inlines_helper_call(), the verifier skips rewriting the helper call offset (insn->imm) in bpf_do_misc_fixups(). This is because the helper is expected to be inlined by the JIT compiler later. Therefore, insn->imm remains as the raw helper enum ID.

However, if JIT is disabled at runtime (net.core.bpf_jit_enable=0) or if JIT compilation fails dynamically (e.g., due to OOM), the program falls back to the BPF interpreter.

When the interpreter executes (__bpf_call_base + insn->imm) with the unpatched raw ID, it jumps into an invalid address space, triggering an instruction alignment fault or a kernel panic.

Although these helpers have valid C implementations in the kernel, the omission of offset rewriting makes runtime interpreter fallback fatal.

Fix this by setting 'prog->jit_required = 1' when helper call rewriting is skipped for JIT inlining. This ensures that such programs are safely rejected if JIT is not available, preventing the runtime kernel panic.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.