From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- net/ipv4/ipmr_base.c | 450 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 450 insertions(+) create mode 100644 net/ipv4/ipmr_base.c (limited to 'net/ipv4/ipmr_base.c') diff --git a/net/ipv4/ipmr_base.c b/net/ipv4/ipmr_base.c new file mode 100644 index 000000000..a0ec6d19a --- /dev/null +++ b/net/ipv4/ipmr_base.c @@ -0,0 +1,450 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Linux multicast routing support + * Common logic shared by IPv4 [ipmr] and IPv6 [ip6mr] implementation + */ + +#include +#include + +/* Sets everything common except 'dev', since that is done under locking */ +void vif_device_init(struct vif_device *v, + struct net_device *dev, + unsigned long rate_limit, + unsigned char threshold, + unsigned short flags, + unsigned short get_iflink_mask) +{ + RCU_INIT_POINTER(v->dev, NULL); + v->bytes_in = 0; + v->bytes_out = 0; + v->pkt_in = 0; + v->pkt_out = 0; + v->rate_limit = rate_limit; + v->flags = flags; + v->threshold = threshold; + if (v->flags & get_iflink_mask) + v->link = dev_get_iflink(dev); + else + v->link = dev->ifindex; +} + +static void __mr_free_table(struct work_struct *work) +{ + struct mr_table *mrt = container_of(to_rcu_work(work), + struct mr_table, work); + + rhltable_destroy(&mrt->mfc_hash); + kfree(mrt); +} + +void mr_table_free(struct mr_table *mrt) +{ + queue_rcu_work(system_dfl_wq, &mrt->work); +} + +struct mr_table * +mr_table_alloc(struct net *net, u32 id, + struct mr_table_ops *ops, + void (*expire_func)(struct timer_list *t), + void (*table_set)(struct mr_table *mrt, + struct net *net)) +{ + struct mr_table *mrt; + int err; + + mrt = kzalloc_obj(*mrt, GFP_KERNEL_ACCOUNT); + if (!mrt) + return ERR_PTR(-ENOMEM); + mrt->id = id; + write_pnet(&mrt->net, net); + + mrt->ops = *ops; + err = rhltable_init(&mrt->mfc_hash, mrt->ops.rht_params); + if (err) { + kfree(mrt); + return ERR_PTR(err); + } + + INIT_RCU_WORK(&mrt->work, __mr_free_table); + INIT_LIST_HEAD(&mrt->mfc_cache_list); + INIT_LIST_HEAD(&mrt->mfc_unres_queue); + + timer_setup(&mrt->ipmr_expire_timer, expire_func, 0); + + mrt->mroute_reg_vif_num = -1; + table_set(mrt, net); + return mrt; +} + +void *mr_mfc_find_parent(struct mr_table *mrt, void *hasharg, int parent) +{ + struct rhlist_head *tmp, *list; + struct mr_mfc *c; + + list = rhltable_lookup(&mrt->mfc_hash, hasharg, *mrt->ops.rht_params); + rhl_for_each_entry_rcu(c, tmp, list, mnode) + if (parent == -1 || parent == c->mfc_parent) + return c; + + return NULL; +} + +void *mr_mfc_find_any_parent(struct mr_table *mrt, int vifi) +{ + struct rhlist_head *tmp, *list; + struct mr_mfc *c; + + list = rhltable_lookup(&mrt->mfc_hash, mrt->ops.cmparg_any, + *mrt->ops.rht_params); + rhl_for_each_entry_rcu(c, tmp, list, mnode) + if (c->mfc_un.res.ttls[vifi] < 255) + return c; + + return NULL; +} + +void *mr_mfc_find_any(struct mr_table *mrt, int vifi, void *hasharg) +{ + struct rhlist_head *tmp, *list; + struct mr_mfc *c, *proxy; + + list = rhltable_lookup(&mrt->mfc_hash, hasharg, *mrt->ops.rht_params); + rhl_for_each_entry_rcu(c, tmp, list, mnode) { + if (c->mfc_un.res.ttls[vifi] < 255) + return c; + + /* It's ok if the vifi is part of the static tree */ + proxy = mr_mfc_find_any_parent(mrt, c->mfc_parent); + if (proxy && proxy->mfc_un.res.ttls[vifi] < 255) + return c; + } + + return mr_mfc_find_any_parent(mrt, vifi); +} + +#ifdef CONFIG_PROC_FS +void *mr_vif_seq_idx(struct net *net, struct mr_vif_iter *iter, loff_t pos) +{ + struct mr_table *mrt = iter->mrt; + + for (iter->ct = 0; iter->ct < mrt->maxvif; ++iter->ct) { + if (!VIF_EXISTS(mrt, iter->ct)) + continue; + if (pos-- == 0) + return &mrt->vif_table[iter->ct]; + } + return NULL; +} + +void *mr_vif_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + struct mr_vif_iter *iter = seq->private; + struct net *net = seq_file_net(seq); + struct mr_table *mrt = iter->mrt; + + ++*pos; + if (v == SEQ_START_TOKEN) + return mr_vif_seq_idx(net, iter, 0); + + while (++iter->ct < mrt->maxvif) { + if (!VIF_EXISTS(mrt, iter->ct)) + continue; + return &mrt->vif_table[iter->ct]; + } + return NULL; +} + +void *mr_mfc_seq_idx(struct net *net, + struct mr_mfc_iter *it, loff_t pos) +{ + struct mr_table *mrt = it->mrt; + struct mr_mfc *mfc; + + rcu_read_lock(); + it->cache = &mrt->mfc_cache_list; + list_for_each_entry_rcu(mfc, &mrt->mfc_cache_list, list) + if (pos-- == 0) + return mfc; + rcu_read_unlock(); + + spin_lock_bh(it->lock); + it->cache = &mrt->mfc_unres_queue; + list_for_each_entry(mfc, it->cache, list) + if (pos-- == 0) + return mfc; + spin_unlock_bh(it->lock); + + it->cache = NULL; + return NULL; +} + +void *mr_mfc_seq_next(struct seq_file *seq, void *v, + loff_t *pos) +{ + struct mr_mfc_iter *it = seq->private; + struct net *net = seq_file_net(seq); + struct mr_table *mrt = it->mrt; + struct mr_mfc *c = v; + + ++*pos; + + if (v == SEQ_START_TOKEN) + return mr_mfc_seq_idx(net, seq->private, 0); + + if (c->list.next != it->cache) + return list_entry(c->list.next, struct mr_mfc, list); + + if (it->cache == &mrt->mfc_unres_queue) + goto end_of_list; + + /* exhausted cache_array, show unresolved */ + rcu_read_unlock(); + it->cache = &mrt->mfc_unres_queue; + + spin_lock_bh(it->lock); + if (!list_empty(it->cache)) + return list_first_entry(it->cache, struct mr_mfc, list); + +end_of_list: + spin_unlock_bh(it->lock); + it->cache = NULL; + + return NULL; +} +#endif + +int mr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb, + struct mr_mfc *c, struct rtmsg *rtm) +{ + struct net_device *vif_dev; + struct rta_mfc_stats mfcs; + struct nlattr *mp_attr; + struct rtnexthop *nhp; + unsigned long lastuse; + int ct; + + /* If cache is unresolved, don't try to parse IIF and OIF */ + if (c->mfc_parent >= MAXVIFS) { + rtm->rtm_flags |= RTNH_F_UNRESOLVED; + return -ENOENT; + } + + rcu_read_lock(); + vif_dev = rcu_dereference(mrt->vif_table[c->mfc_parent].dev); + if (vif_dev && nla_put_u32(skb, RTA_IIF, READ_ONCE(vif_dev->ifindex)) < 0) { + rcu_read_unlock(); + return -EMSGSIZE; + } + rcu_read_unlock(); + + if (c->mfc_flags & MFC_OFFLOAD) + rtm->rtm_flags |= RTNH_F_OFFLOAD; + + mp_attr = nla_nest_start_noflag(skb, RTA_MULTIPATH); + if (!mp_attr) + return -EMSGSIZE; + + rcu_read_lock(); + for (ct = c->mfc_un.res.minvif; ct < c->mfc_un.res.maxvif; ct++) { + struct vif_device *vif = &mrt->vif_table[ct]; + + vif_dev = rcu_dereference(vif->dev); + if (vif_dev && c->mfc_un.res.ttls[ct] < 255) { + + nhp = nla_reserve_nohdr(skb, sizeof(*nhp)); + if (!nhp) { + rcu_read_unlock(); + nla_nest_cancel(skb, mp_attr); + return -EMSGSIZE; + } + + nhp->rtnh_flags = 0; + nhp->rtnh_hops = c->mfc_un.res.ttls[ct]; + nhp->rtnh_ifindex = READ_ONCE(vif_dev->ifindex); + nhp->rtnh_len = sizeof(*nhp); + } + } + rcu_read_unlock(); + + nla_nest_end(skb, mp_attr); + + lastuse = READ_ONCE(c->mfc_un.res.lastuse); + lastuse = time_after_eq(jiffies, lastuse) ? jiffies - lastuse : 0; + + mfcs.mfcs_packets = atomic_long_read(&c->mfc_un.res.pkt); + mfcs.mfcs_bytes = atomic_long_read(&c->mfc_un.res.bytes); + mfcs.mfcs_wrong_if = atomic_long_read(&c->mfc_un.res.wrong_if); + if (nla_put_64bit(skb, RTA_MFC_STATS, sizeof(mfcs), &mfcs, RTA_PAD) || + nla_put_u64_64bit(skb, RTA_EXPIRES, jiffies_to_clock_t(lastuse), + RTA_PAD)) + return -EMSGSIZE; + + rtm->rtm_type = RTN_MULTICAST; + return 1; +} + +static bool mr_mfc_uses_dev(const struct mr_table *mrt, + const struct mr_mfc *c, + const struct net_device *dev) +{ + int ct; + + for (ct = c->mfc_un.res.minvif; ct < c->mfc_un.res.maxvif; ct++) { + const struct net_device *vif_dev; + const struct vif_device *vif; + + vif = &mrt->vif_table[ct]; + vif_dev = rcu_access_pointer(vif->dev); + if (vif_dev && c->mfc_un.res.ttls[ct] < 255 && + vif_dev == dev) + return true; + } + return false; +} + +int mr_table_dump(struct mr_table *mrt, struct sk_buff *skb, + struct netlink_callback *cb, + int (*fill)(struct mr_table *mrt, struct sk_buff *skb, + u32 portid, u32 seq, struct mr_mfc *c, + int cmd, int flags), + spinlock_t *lock, struct fib_dump_filter *filter) +{ + unsigned int e = 0, s_e = cb->args[1]; + unsigned int flags = NLM_F_MULTI; + struct mr_mfc *mfc; + int err; + + if (filter->filter_set) + flags |= NLM_F_DUMP_FILTERED; + + list_for_each_entry_rcu(mfc, &mrt->mfc_cache_list, list, + lockdep_rtnl_is_held()) { + if (e < s_e) + goto next_entry; + if (filter->dev && + !mr_mfc_uses_dev(mrt, mfc, filter->dev)) + goto next_entry; + + err = fill(mrt, skb, NETLINK_CB(cb->skb).portid, + cb->nlh->nlmsg_seq, mfc, RTM_NEWROUTE, flags); + if (err < 0) + goto out; +next_entry: + e++; + } + + spin_lock_bh(lock); + list_for_each_entry(mfc, &mrt->mfc_unres_queue, list) { + if (e < s_e) + goto next_entry2; + + err = fill(mrt, skb, NETLINK_CB(cb->skb).portid, + cb->nlh->nlmsg_seq, mfc, RTM_NEWROUTE, flags); + if (err < 0) { + spin_unlock_bh(lock); + goto out; + } +next_entry2: + e++; + } + spin_unlock_bh(lock); + err = 0; +out: + cb->args[1] = e; + return err; +} + +int mr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb, + struct mr_table *(*iter)(struct net *net, + struct mr_table *mrt), + int (*fill)(struct mr_table *mrt, + struct sk_buff *skb, + u32 portid, u32 seq, struct mr_mfc *c, + int cmd, int flags), + spinlock_t *lock, struct fib_dump_filter *filter) +{ + unsigned int t = 0, s_t = cb->args[0]; + struct net *net = sock_net(skb->sk); + struct mr_table *mrt; + int err; + + /* multicast does not track protocol or have route type other + * than RTN_MULTICAST + */ + if (filter->filter_set) { + if (filter->protocol || filter->flags || + (filter->rt_type && filter->rt_type != RTN_MULTICAST)) + return skb->len; + } + + rcu_read_lock(); + for (mrt = iter(net, NULL); mrt; mrt = iter(net, mrt)) { + if (t < s_t) + goto next_table; + + err = mr_table_dump(mrt, skb, cb, fill, lock, filter); + if (err < 0) + break; + cb->args[1] = 0; +next_table: + t++; + } + rcu_read_unlock(); + + cb->args[0] = t; + + return skb->len; +} + +int mr_dump(struct net *net, struct notifier_block *nb, unsigned short family, + int (*rules_dump)(struct net *net, + struct notifier_block *nb, + struct netlink_ext_ack *extack), + struct mr_table *(*mr_iter)(struct net *net, + struct mr_table *mrt), + struct netlink_ext_ack *extack) +{ + struct mr_table *mrt; + int err; + + err = rules_dump(net, nb, extack); + if (err) + return err; + + for (mrt = mr_iter(net, NULL); mrt; mrt = mr_iter(net, mrt)) { + struct vif_device *v = &mrt->vif_table[0]; + struct net_device *vif_dev; + struct mr_mfc *mfc; + int vifi; + + /* Notifiy on table VIF entries */ + rcu_read_lock(); + for (vifi = 0; vifi < mrt->maxvif; vifi++, v++) { + vif_dev = rcu_dereference(v->dev); + if (!vif_dev) + continue; + + err = mr_call_vif_notifier(nb, family, + FIB_EVENT_VIF_ADD, v, + vif_dev, vifi, + mrt->id, extack); + if (err) + break; + } + rcu_read_unlock(); + + if (err) + return err; + + /* Notify on table MFC entries */ + list_for_each_entry_rcu(mfc, &mrt->mfc_cache_list, list) { + err = mr_call_mfc_notifier(nb, family, + FIB_EVENT_ENTRY_ADD, + mfc, mrt->id, extack); + if (err) + return err; + } + } + + return 0; +} -- cgit v1.3.1