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/batman-adv/hard-interface.h | 149 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 net/batman-adv/hard-interface.h (limited to 'net/batman-adv/hard-interface.h') diff --git a/net/batman-adv/hard-interface.h b/net/batman-adv/hard-interface.h new file mode 100644 index 000000000..935f47ca9 --- /dev/null +++ b/net/batman-adv/hard-interface.h @@ -0,0 +1,149 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) B.A.T.M.A.N. contributors: + * + * Marek Lindner, Simon Wunderlich + */ + +#ifndef _NET_BATMAN_ADV_HARD_INTERFACE_H_ +#define _NET_BATMAN_ADV_HARD_INTERFACE_H_ + +#include "main.h" + +#include +#include +#include +#include +#include +#include +#include + +/** + * enum batadv_hard_if_state - State of a hard interface + */ +enum batadv_hard_if_state { + /** + * @BATADV_IF_TO_BE_REMOVED: interface will be removed from mesh + * interface + */ + BATADV_IF_TO_BE_REMOVED, + + /** @BATADV_IF_INACTIVE: interface is deactivated */ + BATADV_IF_INACTIVE, + + /** @BATADV_IF_ACTIVE: interface is used */ + BATADV_IF_ACTIVE, + + /** @BATADV_IF_TO_BE_ACTIVATED: interface is getting activated */ + BATADV_IF_TO_BE_ACTIVATED, +}; + +/** + * enum batadv_hard_if_bcast - broadcast avoidance options + */ +enum batadv_hard_if_bcast { + /** @BATADV_HARDIF_BCAST_OK: Do broadcast on according hard interface */ + BATADV_HARDIF_BCAST_OK = 0, + + /** + * @BATADV_HARDIF_BCAST_NORECIPIENT: Broadcast not needed, there is no + * recipient + */ + BATADV_HARDIF_BCAST_NORECIPIENT, + + /** + * @BATADV_HARDIF_BCAST_DUPFWD: There is just the neighbor we got it + * from + */ + BATADV_HARDIF_BCAST_DUPFWD, + + /** @BATADV_HARDIF_BCAST_DUPORIG: There is just the originator */ + BATADV_HARDIF_BCAST_DUPORIG, +}; + +extern struct notifier_block batadv_hard_if_notifier; + +struct net_device *__batadv_get_real_netdev(struct net_device *net_device); +struct net_device *batadv_get_real_netdev(struct net_device *net_device); +u32 batadv_netdev_get_wifi_flags(struct net_device *net_dev); +u32 batadv_hardif_get_wifi_flags(struct batadv_hard_iface *hard_iface); +bool batadv_is_wifi_hardif(struct batadv_hard_iface *hard_iface); +struct batadv_hard_iface* +batadv_hardif_get_by_netdev(struct net_device *net_dev); +int batadv_hardif_enable_interface(struct net_device *net_dev, + struct net_device *mesh_iface); +void batadv_hardif_disable_interface(struct batadv_hard_iface *hard_iface); +int batadv_hardif_min_mtu(struct net_device *mesh_iface); +void batadv_update_min_mtu(struct net_device *mesh_iface); +void batadv_hardif_release(struct kref *ref); +int batadv_hardif_no_broadcast(struct batadv_hard_iface *if_outgoing, + u8 *orig_addr, u8 *orig_neigh); +int __init batadv_wifi_net_devices_init(void); +void batadv_wifi_net_devices_deinit(void); + +/** + * batadv_hardif_put() - decrement the hard interface refcounter and possibly + * release it + * @hard_iface: the hard interface to free + */ +static inline void batadv_hardif_put(struct batadv_hard_iface *hard_iface) +{ + if (!hard_iface) + return; + + kref_put(&hard_iface->refcount, batadv_hardif_release); +} + +/** + * batadv_primary_if_get_selected() - Get reference to primary interface + * @bat_priv: the bat priv with all the mesh interface information + * + * Return: primary interface (with increased refcnt), otherwise NULL + */ +static inline struct batadv_hard_iface * +batadv_primary_if_get_selected(struct batadv_priv *bat_priv) +{ + struct batadv_hard_iface *hard_iface; + + rcu_read_lock(); + hard_iface = rcu_dereference(bat_priv->primary_if); + if (!hard_iface) + goto out; + + if (!kref_get_unless_zero(&hard_iface->refcount)) + hard_iface = NULL; + +out: + rcu_read_unlock(); + return hard_iface; +} + +/** + * batadv_is_cfg80211() - check if the given hardif is a cfg80211 + * wifi interface + * @wifi_flags: extracted batadv_hard_iface_wifi_flags of a net_device + * + * Return: true if the net device is a cfg80211 wireless device, false + * otherwise. + */ +static inline bool batadv_is_cfg80211(u32 wifi_flags) +{ + u32 allowed_flags = 0; + + allowed_flags |= BATADV_HARDIF_WIFI_CFG80211_DIRECT; + allowed_flags |= BATADV_HARDIF_WIFI_CFG80211_INDIRECT; + + return !!(wifi_flags & allowed_flags); +} + +/** + * batadv_is_wifi() - check if flags belong to wifi interface + * @wifi_flags: extracted batadv_hard_iface_wifi_flags of a net_device + * + * Return: true if the net device is a 802.11 wireless device, false otherwise. + */ +static inline bool batadv_is_wifi(u32 wifi_flags) +{ + return wifi_flags != 0; +} + +#endif /* _NET_BATMAN_ADV_HARD_INTERFACE_H_ */ -- cgit v1.3.1