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, 65 insertions, 0 deletions

diff --git a/include/net/hotdata.h b/include/net/hotdata.h
new file mode 100644
index 000000000..62534d1f3
--- /dev/null
+++ b/include/net/hotdata.h
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _NET_HOTDATA_H
+#define _NET_HOTDATA_H
+
+#include <linux/llist.h>
+#include <linux/types.h>
+#include <linux/netdevice.h>
+#include <net/protocol.h>
+#ifdef CONFIG_RPS
+#include <net/rps-types.h>
+#endif
+
+struct skb_defer_node {
+	struct llist_head	defer_list;
+	atomic_long_t		defer_count;
+} ____cacheline_aligned_in_smp;
+
+/* Read mostly data used in network fast paths. */
+struct net_hotdata {
+#if IS_ENABLED(CONFIG_INET)
+	struct packet_offload	ip_packet_offload;
+	struct net_offload	tcpv4_offload;
+	struct net_protocol	tcp_protocol;
+	struct net_offload 	udpv4_offload;
+	struct net_protocol	udp_protocol;
+	struct packet_offload	ipv6_packet_offload;
+	struct net_offload	tcpv6_offload;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct inet6_protocol	tcpv6_protocol;
+	struct inet6_protocol	udpv6_protocol;
+#endif
+	struct net_offload	udpv6_offload;
+#endif
+	struct list_head	offload_base;
+	struct kmem_cache	*skbuff_cache;
+	struct kmem_cache	*skbuff_fclone_cache;
+	struct kmem_cache	*skb_small_head_cache;
+#ifdef CONFIG_RPS
+	rps_tag_ptr		rps_sock_flow_table;
+	u32			rps_cpu_mask;
+#endif
+	struct skb_defer_node __percpu *skb_defer_nodes;
+	int			gro_normal_batch;
+	int			netdev_budget;
+	int			netdev_budget_usecs;
+	int			tstamp_prequeue;
+	int			max_backlog;
+	int			qdisc_max_burst;
+	int			dev_tx_weight;
+	int			dev_rx_weight;
+	int			sysctl_max_skb_frags;
+	int			sysctl_skb_defer_max;
+	int			sysctl_mem_pcpu_rsv;
+};
+
+#define inet_ehash_secret	net_hotdata.tcp_protocol.secret
+#define udp_ehash_secret	net_hotdata.udp_protocol.secret
+#define inet6_ehash_secret	net_hotdata.tcpv6_protocol.secret
+#define tcp_ipv6_hash_secret	net_hotdata.tcpv6_offload.secret
+#define udp6_ehash_secret	net_hotdata.udpv6_protocol.secret
+#define udp_ipv6_hash_secret	net_hotdata.udpv6_offload.secret
+
+extern struct net_hotdata net_hotdata;
+
+#endif /* _NET_HOTDATA_H */