x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

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) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 535 insertions, 0 deletions

diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
new file mode 100644
index 000000000..e01c44a90
--- /dev/null
+++ b/net/bridge/br_device.c
@@ -0,0 +1,535 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	Device handling code
+ *	Linux ethernet bridge
+ *
+ *	Authors:
+ *	Lennert Buytenhek		<buytenh@gnu.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/netpoll.h>
+#include <linux/etherdevice.h>
+#include <linux/ethtool.h>
+#include <linux/list.h>
+#include <linux/netfilter_bridge.h>
+
+#include <linux/uaccess.h>
+#include <net/netdev_lock.h>
+
+#include "br_private.h"
+
+#define COMMON_FEATURES (NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA | \
+			 NETIF_F_GSO_MASK | NETIF_F_HW_CSUM)
+
+const struct nf_br_ops __rcu *nf_br_ops __read_mostly;
+EXPORT_SYMBOL_GPL(nf_br_ops);
+
+/* net device transmit always called with BH disabled */
+netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	enum skb_drop_reason reason = pskb_may_pull_reason(skb, ETH_HLEN);
+	struct net_bridge_mcast_port *pmctx_null = NULL;
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_bridge_mcast *brmctx = &br->multicast_ctx;
+	struct net_bridge_fdb_entry *dst;
+	struct net_bridge_mdb_entry *mdst;
+	const struct nf_br_ops *nf_ops;
+	u8 state = BR_STATE_FORWARDING;
+	struct net_bridge_vlan *vlan;
+	const unsigned char *dest;
+	u16 vid = 0;
+
+	if (unlikely(reason != SKB_NOT_DROPPED_YET)) {
+		kfree_skb_reason(skb, reason);
+		return NETDEV_TX_OK;
+	}
+
+	memset(skb->cb, 0, sizeof(struct br_input_skb_cb));
+	br_tc_skb_miss_set(skb, false);
+
+	rcu_read_lock();
+	nf_ops = rcu_dereference(nf_br_ops);
+	if (nf_ops && nf_ops->br_dev_xmit_hook(skb)) {
+		rcu_read_unlock();
+		return NETDEV_TX_OK;
+	}
+
+	dev_sw_netstats_tx_add(dev, 1, skb->len);
+
+	br_switchdev_frame_unmark(skb);
+	BR_INPUT_SKB_CB(skb)->brdev = dev;
+	BR_INPUT_SKB_CB(skb)->frag_max_size = 0;
+
+	skb_reset_mac_header(skb);
+	skb_pull(skb, ETH_HLEN);
+
+	if (!br_allowed_ingress(br, br_vlan_group_rcu(br), skb, &vid,
+				&state, &vlan))
+		goto out;
+
+	if (IS_ENABLED(CONFIG_INET) &&
+	    (eth_hdr(skb)->h_proto == htons(ETH_P_ARP) ||
+	     eth_hdr(skb)->h_proto == htons(ETH_P_RARP)) &&
+	    br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED)) {
+		br_do_proxy_suppress_arp(skb, br, vid, NULL);
+	} else if (ipv6_mod_enabled() &&
+		   skb->protocol == htons(ETH_P_IPV6) &&
+		   br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED) &&
+		   pskb_may_pull(skb, sizeof(struct ipv6hdr) +
+				 sizeof(struct nd_msg)) &&
+		   ipv6_hdr(skb)->nexthdr == IPPROTO_ICMPV6) {
+			struct nd_msg *msg;
+
+			msg = br_is_nd_neigh_msg(skb);
+			if (msg)
+				br_do_suppress_nd(skb, br, vid, NULL, msg);
+	}
+
+	dest = eth_hdr(skb)->h_dest;
+	if (is_broadcast_ether_addr(dest)) {
+		br_flood(br, skb, BR_PKT_BROADCAST, false, true, vid);
+	} else if (is_multicast_ether_addr(dest)) {
+		if (unlikely(netpoll_tx_running(dev))) {
+			br_flood(br, skb, BR_PKT_MULTICAST, false, true, vid);
+			goto out;
+		}
+		if (br_multicast_rcv(&brmctx, &pmctx_null, vlan, skb, vid)) {
+			kfree_skb(skb);
+			goto out;
+		}
+
+		mdst = br_mdb_entry_skb_get(brmctx, skb, vid);
+		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
+		    br_multicast_querier_exists(brmctx, eth_hdr(skb), mdst))
+			br_multicast_flood(mdst, skb, brmctx, false, true);
+		else
+			br_flood(br, skb, BR_PKT_MULTICAST, false, true, vid);
+	} else if ((dst = br_fdb_find_rcu(br, dest, vid)) != NULL) {
+		br_forward(READ_ONCE(dst->dst), skb, false, true);
+	} else {
+		br_flood(br, skb, BR_PKT_UNICAST, false, true, vid);
+	}
+out:
+	rcu_read_unlock();
+	return NETDEV_TX_OK;
+}
+
+static int br_dev_init(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	int err;
+
+	err = br_fdb_hash_init(br);
+	if (err)
+		return err;
+
+	err = br_mdb_hash_init(br);
+	if (err) {
+		br_fdb_hash_fini(br);
+		return err;
+	}
+
+	err = br_vlan_init(br);
+	if (err) {
+		br_mdb_hash_fini(br);
+		br_fdb_hash_fini(br);
+		return err;
+	}
+
+	err = br_multicast_init_stats(br);
+	if (err) {
+		br_vlan_flush(br);
+		br_mdb_hash_fini(br);
+		br_fdb_hash_fini(br);
+		return err;
+	}
+
+	netdev_lockdep_set_classes(dev);
+	return 0;
+}
+
+static void br_dev_uninit(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	br_multicast_dev_del(br);
+	br_multicast_uninit_stats(br);
+	br_vlan_flush(br);
+	br_mdb_hash_fini(br);
+	br_fdb_hash_fini(br);
+}
+
+static int br_dev_open(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	netdev_update_features(dev);
+	netif_start_queue(dev);
+	br_stp_enable_bridge(br);
+	br_multicast_open(br);
+
+	if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
+		br_multicast_join_snoopers(br);
+
+	return 0;
+}
+
+static void br_dev_set_multicast_list(struct net_device *dev)
+{
+}
+
+static void br_dev_change_rx_flags(struct net_device *dev, int change)
+{
+	if (change & IFF_PROMISC)
+		br_manage_promisc(netdev_priv(dev));
+}
+
+static int br_dev_stop(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	br_stp_disable_bridge(br);
+	br_multicast_stop(br);
+
+	if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
+		br_multicast_leave_snoopers(br);
+
+	netif_stop_queue(dev);
+
+	return 0;
+}
+
+static int br_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	WRITE_ONCE(dev->mtu, new_mtu);
+
+	/* this flag will be cleared if the MTU was automatically adjusted */
+	br_opt_toggle(br, BROPT_MTU_SET_BY_USER, true);
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
+	/* remember the MTU in the rtable for PMTU */
+	dst_metric_set(&br->fake_rtable.dst, RTAX_MTU, new_mtu);
+#endif
+
+	return 0;
+}
+
+/* Allow setting mac address to any valid ethernet address. */
+static int br_set_mac_address(struct net_device *dev, void *p)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct sockaddr *addr = p;
+
+	if (!is_valid_ether_addr(addr->sa_data))
+		return -EADDRNOTAVAIL;
+
+	/* dev_set_mac_addr() can be called by a master device on bridge's
+	 * NETDEV_UNREGISTER, but since it's being destroyed do nothing
+	 */
+	if (dev->reg_state != NETREG_REGISTERED)
+		return -EBUSY;
+
+	spin_lock_bh(&br->lock);
+	if (!ether_addr_equal(dev->dev_addr, addr->sa_data)) {
+		/* Mac address will be changed in br_stp_change_bridge_id(). */
+		br_stp_change_bridge_id(br, addr->sa_data);
+	}
+	spin_unlock_bh(&br->lock);
+
+	return 0;
+}
+
+static void br_getinfo(struct net_device *dev, struct ethtool_drvinfo *info)
+{
+	strscpy(info->driver, "bridge", sizeof(info->driver));
+	strscpy(info->version, BR_VERSION, sizeof(info->version));
+	strscpy(info->fw_version, "N/A", sizeof(info->fw_version));
+	strscpy(info->bus_info, "N/A", sizeof(info->bus_info));
+}
+
+static int br_get_link_ksettings(struct net_device *dev,
+				 struct ethtool_link_ksettings *cmd)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_bridge_port *p;
+
+	cmd->base.duplex = DUPLEX_UNKNOWN;
+	cmd->base.port = PORT_OTHER;
+	cmd->base.speed = SPEED_UNKNOWN;
+
+	list_for_each_entry(p, &br->port_list, list) {
+		struct ethtool_link_ksettings ecmd;
+		struct net_device *pdev = p->dev;
+
+		if (!netif_running(pdev) || !netif_oper_up(pdev))
+			continue;
+
+		if (__ethtool_get_link_ksettings(pdev, &ecmd))
+			continue;
+
+		if (ecmd.base.speed == (__u32)SPEED_UNKNOWN)
+			continue;
+
+		if (cmd->base.speed == (__u32)SPEED_UNKNOWN ||
+		    cmd->base.speed < ecmd.base.speed)
+			cmd->base.speed = ecmd.base.speed;
+	}
+
+	return 0;
+}
+
+static netdev_features_t br_fix_features(struct net_device *dev,
+	netdev_features_t features)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	return br_features_recompute(br, features);
+}
+
+#ifdef CONFIG_NET_POLL_CONTROLLER
+static void br_poll_controller(struct net_device *br_dev)
+{
+}
+
+static void br_netpoll_cleanup(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_bridge_port *p;
+
+	list_for_each_entry(p, &br->port_list, list)
+		br_netpoll_disable(p);
+}
+
+static int __br_netpoll_enable(struct net_bridge_port *p)
+{
+	struct netpoll *np;
+	int err;
+
+	np = kzalloc_obj(*p->np);
+	if (!np)
+		return -ENOMEM;
+
+	err = __netpoll_setup(np, p->dev);
+	if (err) {
+		kfree(np);
+		return err;
+	}
+
+	p->np = np;
+	return err;
+}
+
+int br_netpoll_enable(struct net_bridge_port *p)
+{
+	if (!p->br->dev->npinfo)
+		return 0;
+
+	return __br_netpoll_enable(p);
+}
+
+static int br_netpoll_setup(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_bridge_port *p;
+	int err = 0;
+
+	list_for_each_entry(p, &br->port_list, list) {
+		if (!p->dev)
+			continue;
+		err = __br_netpoll_enable(p);
+		if (err)
+			goto fail;
+	}
+
+out:
+	return err;
+
+fail:
+	br_netpoll_cleanup(dev);
+	goto out;
+}
+
+void br_netpoll_disable(struct net_bridge_port *p)
+{
+	struct netpoll *np = p->np;
+
+	if (!np)
+		return;
+
+	p->np = NULL;
+
+	__netpoll_free(np);
+}
+
+#endif
+
+static int br_add_slave(struct net_device *dev, struct net_device *slave_dev,
+			struct netlink_ext_ack *extack)
+
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	return br_add_if(br, slave_dev, extack);
+}
+
+static int br_del_slave(struct net_device *dev, struct net_device *slave_dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	return br_del_if(br, slave_dev);
+}
+
+static int br_fill_forward_path(struct net_device_path_ctx *ctx,
+				struct net_device_path *path)
+{
+	struct net_bridge_fdb_entry *f;
+	struct net_bridge_port *dst;
+	struct net_bridge *br;
+
+	if (netif_is_bridge_port(ctx->dev))
+		return -1;
+
+	br = netdev_priv(ctx->dev);
+
+	br_vlan_fill_forward_path_pvid(br, ctx, path);
+
+	f = br_fdb_find_rcu(br, ctx->daddr, path->bridge.vlan_id);
+	if (!f)
+		return -1;
+
+	dst = READ_ONCE(f->dst);
+	if (!dst)
+		return -1;
+
+	if (br_vlan_fill_forward_path_mode(br, dst, path))
+		return -1;
+
+	path->type = DEV_PATH_BRIDGE;
+	path->dev = dst->br->dev;
+	ctx->dev = dst->dev;
+
+	switch (path->bridge.vlan_mode) {
+	case DEV_PATH_BR_VLAN_TAG:
+		if (ctx->num_vlans >= ARRAY_SIZE(ctx->vlan))
+			return -ENOSPC;
+		ctx->vlan[ctx->num_vlans].id = path->bridge.vlan_id;
+		ctx->vlan[ctx->num_vlans].proto = path->bridge.vlan_proto;
+		ctx->num_vlans++;
+		break;
+	case DEV_PATH_BR_VLAN_UNTAG_HW:
+	case DEV_PATH_BR_VLAN_UNTAG:
+		ctx->num_vlans--;
+		break;
+	case DEV_PATH_BR_VLAN_KEEP:
+		break;
+	}
+
+	return 0;
+}
+
+static const struct ethtool_ops br_ethtool_ops = {
+	.get_drvinfo		 = br_getinfo,
+	.get_link		 = ethtool_op_get_link,
+	.get_link_ksettings	 = br_get_link_ksettings,
+};
+
+static const struct net_device_ops br_netdev_ops = {
+	.ndo_open		 = br_dev_open,
+	.ndo_stop		 = br_dev_stop,
+	.ndo_init		 = br_dev_init,
+	.ndo_uninit		 = br_dev_uninit,
+	.ndo_start_xmit		 = br_dev_xmit,
+	.ndo_get_stats64	 = dev_get_tstats64,
+	.ndo_set_mac_address	 = br_set_mac_address,
+	.ndo_set_rx_mode	 = br_dev_set_multicast_list,
+	.ndo_change_rx_flags	 = br_dev_change_rx_flags,
+	.ndo_change_mtu		 = br_change_mtu,
+	.ndo_siocdevprivate	 = br_dev_siocdevprivate,
+#ifdef CONFIG_NET_POLL_CONTROLLER
+	.ndo_netpoll_setup	 = br_netpoll_setup,
+	.ndo_netpoll_cleanup	 = br_netpoll_cleanup,
+	.ndo_poll_controller	 = br_poll_controller,
+#endif
+	.ndo_add_slave		 = br_add_slave,
+	.ndo_del_slave		 = br_del_slave,
+	.ndo_fix_features        = br_fix_features,
+	.ndo_fdb_add		 = br_fdb_add,
+	.ndo_fdb_del		 = br_fdb_delete,
+	.ndo_fdb_del_bulk	 = br_fdb_delete_bulk,
+	.ndo_fdb_dump		 = br_fdb_dump,
+	.ndo_fdb_get		 = br_fdb_get,
+	.ndo_mdb_add		 = br_mdb_add,
+	.ndo_mdb_del		 = br_mdb_del,
+	.ndo_mdb_del_bulk	 = br_mdb_del_bulk,
+	.ndo_mdb_dump		 = br_mdb_dump,
+	.ndo_mdb_get		 = br_mdb_get,
+	.ndo_bridge_getlink	 = br_getlink,
+	.ndo_bridge_setlink	 = br_setlink,
+	.ndo_bridge_dellink	 = br_dellink,
+	.ndo_features_check	 = passthru_features_check,
+	.ndo_fill_forward_path	 = br_fill_forward_path,
+};
+
+static const struct device_type br_type = {
+	.name	= "bridge",
+};
+
+void br_dev_setup(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	eth_hw_addr_random(dev);
+	ether_setup(dev);
+
+	dev->netdev_ops = &br_netdev_ops;
+	dev->needs_free_netdev = true;
+	dev->ethtool_ops = &br_ethtool_ops;
+	SET_NETDEV_DEVTYPE(dev, &br_type);
+	dev->priv_flags = IFF_EBRIDGE | IFF_NO_QUEUE;
+	dev->lltx = true;
+	dev->netns_immutable = true;
+
+	dev->features = COMMON_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
+			NETIF_F_HW_VLAN_STAG_TX;
+	dev->hw_features = COMMON_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
+			   NETIF_F_HW_VLAN_STAG_TX;
+	dev->vlan_features = COMMON_FEATURES;
+	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
+
+	br->dev = dev;
+	spin_lock_init(&br->lock);
+	INIT_LIST_HEAD(&br->port_list);
+	INIT_HLIST_HEAD(&br->fdb_list);
+#if IS_ENABLED(CONFIG_BRIDGE_MRP)
+	INIT_HLIST_HEAD(&br->mrp_list);
+#endif
+#if IS_ENABLED(CONFIG_BRIDGE_CFM)
+	INIT_HLIST_HEAD(&br->mep_list);
+#endif
+	spin_lock_init(&br->hash_lock);
+
+	br->bridge_id.prio[0] = 0x80;
+	br->bridge_id.prio[1] = 0x00;
+
+	ether_addr_copy(br->group_addr, eth_stp_addr);
+
+	br->stp_enabled = BR_NO_STP;
+	br->stp_mode = BR_STP_MODE_AUTO;
+	br->group_fwd_mask = BR_GROUPFWD_DEFAULT;
+	br->group_fwd_mask_required = BR_GROUPFWD_DEFAULT;
+
+	br->designated_root = br->bridge_id;
+	br->bridge_max_age = br->max_age = 20 * HZ;
+	br->bridge_hello_time = br->hello_time = 2 * HZ;
+	br->bridge_forward_delay = br->forward_delay = 15 * HZ;
+	br->bridge_ageing_time = br->ageing_time = BR_DEFAULT_AGEING_TIME;
+	dev->max_mtu = ETH_MAX_MTU;
+
+	br_netfilter_rtable_init(br);
+	br_stp_timer_init(br);
+	br_multicast_init(br);
+	INIT_DELAYED_WORK(&br->gc_work, br_fdb_cleanup);
+}