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, 63 insertions, 0 deletions

diff --git a/fs/smb/server/misc.h b/fs/smb/server/misc.h
new file mode 100644
index 000000000..1faaddd0f
--- /dev/null
+++ b/fs/smb/server/misc.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *   Copyright (C) 2018 Samsung Electronics Co., Ltd.
+ */
+
+#ifndef __KSMBD_MISC_H__
+#define __KSMBD_MISC_H__
+
+#ifdef CONFIG_PROC_FS
+#include <linux/proc_fs.h>
+#endif
+struct ksmbd_share_config;
+struct nls_table;
+struct kstat;
+struct ksmbd_file;
+
+int match_pattern(const char *str, size_t len, const char *pattern);
+int ksmbd_validate_filename(char *filename);
+int parse_stream_name(char *filename, char **stream_name, int *s_type);
+char *convert_to_nt_pathname(struct ksmbd_share_config *share,
+			     const struct path *path);
+int get_nlink(struct kstat *st);
+void ksmbd_conv_path_to_unix(char *path);
+void ksmbd_strip_last_slash(char *path);
+void ksmbd_conv_path_to_windows(char *path);
+char *ksmbd_casefold_sharename(struct unicode_map *um, const char *name);
+char *ksmbd_extract_sharename(struct unicode_map *um, const char *treename);
+
+#define KSMBD_DIR_INFO_ALIGNMENT	8
+struct ksmbd_dir_info;
+char *ksmbd_convert_dir_info_name(struct ksmbd_dir_info *d_info,
+				  const struct nls_table *local_nls,
+				  int *conv_len);
+
+#define NTFS_TIME_OFFSET	((u64)(369 * 365 + 89) * 24 * 3600 * 10000000)
+struct timespec64 ksmbd_NTtimeToUnix(__le64 ntutc);
+u64 ksmbd_UnixTimeToNT(struct timespec64 t);
+long long ksmbd_systime(void);
+
+#ifdef CONFIG_PROC_FS
+struct ksmbd_const_name {
+	unsigned int const_value;
+	const char *name;
+};
+
+int ksmbd_proc_init(void);
+void ksmbd_proc_cleanup(void);
+void ksmbd_proc_reset(void);
+struct proc_dir_entry *ksmbd_proc_create(const char *name,
+					 int (*show)(struct seq_file *m, void *v),
+			     void *v);
+void ksmbd_proc_show_flag_names(struct seq_file *m,
+				const struct ksmbd_const_name *table,
+				int count,
+				unsigned int flags);
+const char *ksmbd_proc_const_name(const struct ksmbd_const_name *table,
+				  int count, unsigned int const_value);
+#else
+static inline int ksmbd_proc_init(void) { return 0; }
+static inline void ksmbd_proc_cleanup(void) {}
+static inline void ksmbd_proc_reset(void) {}
+#endif
+#endif /* __KSMBD_MISC_H__ */