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, 77 insertions, 0 deletions

diff --git a/fs/smb/server/server.h b/fs/smb/server/server.h
new file mode 100644
index 000000000..4d4d268b5
--- /dev/null
+++ b/fs/smb/server/server.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *   Copyright (C) 2018 Samsung Electronics Co., Ltd.
+ */
+
+#ifndef __SERVER_H__
+#define __SERVER_H__
+
+#include "smbacl.h"
+
+/*
+ * Server state type
+ */
+enum {
+	SERVER_STATE_STARTING_UP,
+	SERVER_STATE_RUNNING,
+	SERVER_STATE_RESETTING,
+	SERVER_STATE_SHUTTING_DOWN,
+};
+
+/*
+ * Server global config string index
+ */
+enum {
+	SERVER_CONF_NETBIOS_NAME,
+	SERVER_CONF_SERVER_STRING,
+	SERVER_CONF_WORK_GROUP,
+};
+
+struct ksmbd_server_config {
+	unsigned int		flags;
+	unsigned int		state;
+	short			signing;
+	short			enforced_signing;
+	short			min_protocol;
+	short			max_protocol;
+	unsigned short		tcp_port;
+	unsigned short		ipc_timeout;
+	unsigned long		ipc_last_active;
+	unsigned long		deadtime;
+	unsigned int		share_fake_fscaps;
+	struct smb_sid		domain_sid;
+	unsigned int		auth_mechs;
+	unsigned int		max_connections;
+	unsigned int		max_inflight_req;
+	unsigned int		max_ip_connections;
+
+	char			*conf[SERVER_CONF_WORK_GROUP + 1];
+	struct task_struct	*dh_task;
+	bool			bind_interfaces_only;
+	/* AAPL model string for Finder icon, e.g. "Xserve" */
+	char			aapl_model[32];
+};
+
+extern struct ksmbd_server_config server_conf;
+
+int ksmbd_set_netbios_name(char *v);
+int ksmbd_set_server_string(char *v);
+int ksmbd_set_work_group(char *v);
+
+char *ksmbd_netbios_name(void);
+char *ksmbd_server_string(void);
+char *ksmbd_work_group(void);
+
+static inline int ksmbd_server_running(void)
+{
+	return READ_ONCE(server_conf.state) == SERVER_STATE_RUNNING;
+}
+
+static inline int ksmbd_server_configurable(void)
+{
+	return READ_ONCE(server_conf.state) < SERVER_STATE_RESETTING;
+}
+
+int server_queue_ctrl_init_work(void);
+int server_queue_ctrl_reset_work(void);
+#endif /* __SERVER_H__ */