![Daniel Borkmann](/assets/img/avatar_default.png)
syzkaller was able to generate the following XDP program ...
(18) r0 = 0x0
(61) r5 = *(u32 *)(r1 +12)
(04) (u32) r0 += (u32) 0
(95) exit
... and trigger a NULL pointer dereference in ___bpf_prog_run()
via bpf_prog_test_run_xdp() where this was attempted to run.
Reason is that recent xdp_rxq_info addition to XDP programs
updated all drivers, but not bpf_prog_test_run_xdp(), where
xdp_buff is set up. Thus when context rewriter does the deref
on the netdev it's NULL at runtime. Fix it by using xdp_rxq
from loopback dev. __netif_get_rx_queue() helper can also be
reused in various other locations later on.
Fixes: 02dd3291b2
("bpf: finally expose xdp_rxq_info to XDP bpf-programs")
Reported-by: syzbot+1eb094057b338eb1fc00@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
179 lines
4.5 KiB
C
179 lines
4.5 KiB
C
/* Copyright (c) 2017 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <linux/bpf.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/etherdevice.h>
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#include <linux/filter.h>
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#include <linux/sched/signal.h>
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static __always_inline u32 bpf_test_run_one(struct bpf_prog *prog, void *ctx)
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{
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u32 ret;
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preempt_disable();
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rcu_read_lock();
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ret = BPF_PROG_RUN(prog, ctx);
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rcu_read_unlock();
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preempt_enable();
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return ret;
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}
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static u32 bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat, u32 *time)
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{
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u64 time_start, time_spent = 0;
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u32 ret = 0, i;
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if (!repeat)
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repeat = 1;
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time_start = ktime_get_ns();
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for (i = 0; i < repeat; i++) {
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ret = bpf_test_run_one(prog, ctx);
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if (need_resched()) {
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if (signal_pending(current))
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break;
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time_spent += ktime_get_ns() - time_start;
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cond_resched();
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time_start = ktime_get_ns();
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}
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}
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time_spent += ktime_get_ns() - time_start;
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do_div(time_spent, repeat);
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*time = time_spent > U32_MAX ? U32_MAX : (u32)time_spent;
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return ret;
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}
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static int bpf_test_finish(const union bpf_attr *kattr,
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union bpf_attr __user *uattr, const void *data,
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u32 size, u32 retval, u32 duration)
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{
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void __user *data_out = u64_to_user_ptr(kattr->test.data_out);
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int err = -EFAULT;
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if (data_out && copy_to_user(data_out, data, size))
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goto out;
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if (copy_to_user(&uattr->test.data_size_out, &size, sizeof(size)))
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goto out;
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if (copy_to_user(&uattr->test.retval, &retval, sizeof(retval)))
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goto out;
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if (copy_to_user(&uattr->test.duration, &duration, sizeof(duration)))
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goto out;
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err = 0;
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out:
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return err;
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}
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static void *bpf_test_init(const union bpf_attr *kattr, u32 size,
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u32 headroom, u32 tailroom)
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{
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void __user *data_in = u64_to_user_ptr(kattr->test.data_in);
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void *data;
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if (size < ETH_HLEN || size > PAGE_SIZE - headroom - tailroom)
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return ERR_PTR(-EINVAL);
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data = kzalloc(size + headroom + tailroom, GFP_USER);
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if (!data)
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return ERR_PTR(-ENOMEM);
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if (copy_from_user(data + headroom, data_in, size)) {
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kfree(data);
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return ERR_PTR(-EFAULT);
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}
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return data;
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}
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int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
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union bpf_attr __user *uattr)
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{
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bool is_l2 = false, is_direct_pkt_access = false;
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u32 size = kattr->test.data_size_in;
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u32 repeat = kattr->test.repeat;
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u32 retval, duration;
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struct sk_buff *skb;
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void *data;
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int ret;
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data = bpf_test_init(kattr, size, NET_SKB_PAD + NET_IP_ALIGN,
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SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
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if (IS_ERR(data))
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return PTR_ERR(data);
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switch (prog->type) {
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case BPF_PROG_TYPE_SCHED_CLS:
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case BPF_PROG_TYPE_SCHED_ACT:
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is_l2 = true;
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/* fall through */
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case BPF_PROG_TYPE_LWT_IN:
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case BPF_PROG_TYPE_LWT_OUT:
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case BPF_PROG_TYPE_LWT_XMIT:
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is_direct_pkt_access = true;
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break;
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default:
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break;
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}
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skb = build_skb(data, 0);
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if (!skb) {
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kfree(data);
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return -ENOMEM;
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}
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skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
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__skb_put(skb, size);
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skb->protocol = eth_type_trans(skb, current->nsproxy->net_ns->loopback_dev);
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skb_reset_network_header(skb);
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if (is_l2)
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__skb_push(skb, ETH_HLEN);
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if (is_direct_pkt_access)
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bpf_compute_data_pointers(skb);
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retval = bpf_test_run(prog, skb, repeat, &duration);
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if (!is_l2)
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__skb_push(skb, ETH_HLEN);
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size = skb->len;
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/* bpf program can never convert linear skb to non-linear */
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if (WARN_ON_ONCE(skb_is_nonlinear(skb)))
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size = skb_headlen(skb);
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ret = bpf_test_finish(kattr, uattr, skb->data, size, retval, duration);
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kfree_skb(skb);
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return ret;
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}
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int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
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union bpf_attr __user *uattr)
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{
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u32 size = kattr->test.data_size_in;
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u32 repeat = kattr->test.repeat;
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struct netdev_rx_queue *rxqueue;
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struct xdp_buff xdp = {};
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u32 retval, duration;
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void *data;
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int ret;
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data = bpf_test_init(kattr, size, XDP_PACKET_HEADROOM + NET_IP_ALIGN, 0);
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if (IS_ERR(data))
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return PTR_ERR(data);
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xdp.data_hard_start = data;
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xdp.data = data + XDP_PACKET_HEADROOM + NET_IP_ALIGN;
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xdp.data_meta = xdp.data;
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xdp.data_end = xdp.data + size;
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rxqueue = __netif_get_rx_queue(current->nsproxy->net_ns->loopback_dev, 0);
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xdp.rxq = &rxqueue->xdp_rxq;
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retval = bpf_test_run(prog, &xdp, repeat, &duration);
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if (xdp.data != data + XDP_PACKET_HEADROOM + NET_IP_ALIGN)
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size = xdp.data_end - xdp.data;
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ret = bpf_test_finish(kattr, uattr, xdp.data, size, retval, duration);
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kfree(data);
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return ret;
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}
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