From e582778f023b4c9e608b5cca135f17f62b0cd115 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Wed, 9 Apr 2025 14:46:02 -0700 Subject: [PATCH] bpf: net_sched: Disable attaching bpf qdisc to non root MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Do not allow users to attach bpf qdiscs to classful qdiscs. This is to prevent accidentally breaking existings classful qdiscs if they rely on some data in the child qdisc. This restriction can potentially be lifted in the future. Note that, we still allow bpf qdisc to be attached to mq. Signed-off-by: Amery Hung Signed-off-by: Martin KaFai Lau Acked-by: Toke Høiland-Jørgensen Link: https://patch.msgid.link/20250409214606.2000194-7-ameryhung@gmail.com --- net/sched/bpf_qdisc.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c index dcbd1c927634..9f32b305636f 100644 --- a/net/sched/bpf_qdisc.c +++ b/net/sched/bpf_qdisc.c @@ -142,13 +142,19 @@ static int bpf_qdisc_gen_prologue(struct bpf_insn *insn_buf, bool direct_write, return 0; /* r6 = r1; // r6 will be "u64 *ctx". r1 is "u64 *ctx". + * r2 = r1[16]; // r2 will be "struct netlink_ext_ack *extack" * r1 = r1[0]; // r1 will be "struct Qdisc *sch" - * r0 = bpf_qdisc_init_prologue(r1); + * r0 = bpf_qdisc_init_prologue(r1, r2); + * if r0 == 0 goto pc+1; + * BPF_EXIT; * r1 = r6; // r1 will be "u64 *ctx". */ *insn++ = BPF_MOV64_REG(BPF_REG_6, BPF_REG_1); + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_1, 16); *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0); *insn++ = BPF_CALL_KFUNC(0, bpf_qdisc_init_prologue_ids[0]); + *insn++ = BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1); + *insn++ = BPF_EXIT_INSN(); *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_6); *insn++ = prog->insnsi[0]; @@ -221,11 +227,26 @@ __bpf_kfunc void bpf_qdisc_watchdog_schedule(struct Qdisc *sch, u64 expire, u64 } /* bpf_qdisc_init_prologue - Hidden kfunc called in prologue of .init. */ -__bpf_kfunc void bpf_qdisc_init_prologue(struct Qdisc *sch) +__bpf_kfunc int bpf_qdisc_init_prologue(struct Qdisc *sch, + struct netlink_ext_ack *extack) { struct bpf_sched_data *q = qdisc_priv(sch); + struct net_device *dev = qdisc_dev(sch); + struct Qdisc *p; + + if (sch->parent != TC_H_ROOT) { + p = qdisc_lookup(dev, TC_H_MAJ(sch->parent)); + if (!p) + return -ENOENT; + + if (!(p->flags & TCQ_F_MQROOT)) { + NL_SET_ERR_MSG(extack, "BPF qdisc only supported on root or mq"); + return -EINVAL; + } + } qdisc_watchdog_init(&q->watchdog, sch); + return 0; } /* bpf_qdisc_reset_destroy_epilogue - Hidden kfunc called in epilogue of .reset -- 2.50.1