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, 116 insertions, 0 deletions

diff --git a/net/batman-adv/send.h b/net/batman-adv/send.h
new file mode 100644
index 000000000..3415afec4
--- /dev/null
+++ b/net/batman-adv/send.h
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) B.A.T.M.A.N. contributors:
+ *
+ * Marek Lindner, Simon Wunderlich
+ */
+
+#ifndef _NET_BATMAN_ADV_SEND_H_
+#define _NET_BATMAN_ADV_SEND_H_
+
+#include "main.h"
+
+#include <linux/compiler.h>
+#include <linux/skbuff.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <uapi/linux/batadv_packet.h>
+
+void batadv_forw_packet_free(struct batadv_forw_packet *forw_packet,
+			     bool dropped);
+struct batadv_forw_packet *
+batadv_forw_packet_alloc(struct batadv_hard_iface *if_incoming,
+			 struct batadv_hard_iface *if_outgoing,
+			 atomic_t *queue_left,
+			 struct batadv_priv *bat_priv,
+			 struct sk_buff *skb);
+bool batadv_forw_packet_steal(struct batadv_forw_packet *packet, spinlock_t *l);
+void batadv_forw_packet_ogmv1_queue(struct batadv_priv *bat_priv,
+				    struct batadv_forw_packet *forw_packet,
+				    unsigned long send_time);
+bool batadv_forw_packet_is_rebroadcast(struct batadv_forw_packet *forw_packet);
+
+int batadv_send_skb_to_orig(struct sk_buff *skb,
+			    struct batadv_orig_node *orig_node,
+			    struct batadv_hard_iface *recv_if);
+int batadv_send_skb_packet(struct sk_buff *skb,
+			   struct batadv_hard_iface *hard_iface,
+			   const u8 *dst_addr);
+int batadv_send_broadcast_skb(struct sk_buff *skb,
+			      struct batadv_hard_iface *hard_iface);
+int batadv_send_unicast_skb(struct sk_buff *skb,
+			    struct batadv_neigh_node *neigh_node);
+int batadv_forw_bcast_packet(struct batadv_priv *bat_priv,
+			     struct sk_buff *skb,
+			     unsigned long delay,
+			     bool own_packet);
+void batadv_send_bcast_packet(struct batadv_priv *bat_priv,
+			      struct sk_buff *skb,
+			      unsigned long delay,
+			      bool own_packet);
+void
+batadv_purge_outstanding_packets(struct batadv_priv *bat_priv,
+				 const struct batadv_hard_iface *hard_iface);
+bool batadv_send_skb_prepare_unicast_4addr(struct batadv_priv *bat_priv,
+					   struct sk_buff *skb,
+					   struct batadv_orig_node *orig_node,
+					   int packet_subtype);
+int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
+			    struct sk_buff *skb, int packet_type,
+			    int packet_subtype,
+			    struct batadv_orig_node *orig_node,
+			    unsigned short vid);
+int batadv_send_skb_via_tt_generic(struct batadv_priv *bat_priv,
+				   struct sk_buff *skb, int packet_type,
+				   int packet_subtype, u8 *dst_hint,
+				   unsigned short vid);
+int batadv_send_skb_via_gw(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			   unsigned short vid);
+
+/**
+ * batadv_send_skb_via_tt() - send an skb via TT lookup
+ * @bat_priv: the bat priv with all the mesh interface information
+ * @skb: the payload to send
+ * @dst_hint: can be used to override the destination contained in the skb
+ * @vid: the vid to be used to search the translation table
+ *
+ * Look up the recipient node for the destination address in the ethernet
+ * header via the translation table. Wrap the given skb into a batman-adv
+ * unicast header. Then send this frame to the according destination node.
+ *
+ * Return: NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
+ */
+static inline int batadv_send_skb_via_tt(struct batadv_priv *bat_priv,
+					 struct sk_buff *skb, u8 *dst_hint,
+					 unsigned short vid)
+{
+	return batadv_send_skb_via_tt_generic(bat_priv, skb, BATADV_UNICAST, 0,
+					      dst_hint, vid);
+}
+
+/**
+ * batadv_send_skb_via_tt_4addr() - send an skb via TT lookup
+ * @bat_priv: the bat priv with all the mesh interface information
+ * @skb: the payload to send
+ * @packet_subtype: the unicast 4addr packet subtype to use
+ * @dst_hint: can be used to override the destination contained in the skb
+ * @vid: the vid to be used to search the translation table
+ *
+ * Look up the recipient node for the destination address in the ethernet
+ * header via the translation table. Wrap the given skb into a batman-adv
+ * unicast-4addr header. Then send this frame to the according destination
+ * node.
+ *
+ * Return: NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
+ */
+static inline int batadv_send_skb_via_tt_4addr(struct batadv_priv *bat_priv,
+					       struct sk_buff *skb,
+					       int packet_subtype,
+					       u8 *dst_hint,
+					       unsigned short vid)
+{
+	return batadv_send_skb_via_tt_generic(bat_priv, skb,
+					      BATADV_UNICAST_4ADDR,
+					      packet_subtype, dst_hint, vid);
+}
+
+#endif /* _NET_BATMAN_ADV_SEND_H_ */