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bpf, x86: Sign-extend narrow signed kfunc returns #13416

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bpf, x86: Sign-extend narrow signed kfunc returns #13416

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22 changes: 22 additions & 0 deletions arch/x86/net/bpf_jit_comp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1721,6 +1721,23 @@ static int emit_kfunc_arena_args(struct bpf_prog *bpf_prog,
return prog - start;
}

static int emit_kfunc_return(const struct bpf_prog *bpf_prog,
const struct bpf_insn *insn, u8 **pprog)
{
const struct btf_func_model *fm;

fm = bpf_jit_find_kfunc_model(bpf_prog, insn);
if (!fm)
return -EINVAL;
if (!(fm->ret_flags & BTF_FMODEL_SIGNED_ARG) || fm->ret_size == 8)
return 0;
if (fm->ret_size != 1 && fm->ret_size != 2 && fm->ret_size != 4)
return -EINVAL;

emit_movsx_reg(pprog, fm->ret_size * 8, true, BPF_REG_0, BPF_REG_0);
return 0;
}

static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int *addrs, u8 *image,
u8 *rw_image, int oldproglen, struct jit_context *ctx, bool jmp_padding)
{
Expand Down Expand Up @@ -2664,6 +2681,11 @@ st: insn_off = insn->off;
ip += x86_call_depth_emit_accounting(&prog, func, ip);
if (emit_call(&prog, func, ip))
return -EINVAL;
if (src_reg == BPF_PSEUDO_KFUNC_CALL) {
err = emit_kfunc_return(bpf_prog, insn, &prog);
if (err)
return err;
}
if (priv_frame_ptr)
pop_r9(&prog);
/*
Expand Down
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