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

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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.

Fixes: 2ddec2c80b ("riscv, bpf: inline bpf_get_smp_processor_id()")
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Suggested-by: KaFai Wan <kafai.wan@linux.dev>
Acked-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

...

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Tiezhu Yang 2026-07-08 18:18:06 +08:00 • committed by Eduard Zingerman

parent 9a6df65d5c

commit f1c2792257

1 changed files with 3 additions and 1 deletions

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kernel/bpf/fixups.c

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