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, 85 insertions, 0 deletions

diff --git a/fs/dlm/lock.h b/fs/dlm/lock.h
new file mode 100644
index 000000000..b23d7b854
--- /dev/null
+++ b/fs/dlm/lock.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) 2005-2007 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+#ifndef __LOCK_DOT_H__
+#define __LOCK_DOT_H__
+
+void dlm_dump_rsb(struct dlm_rsb *r);
+void dlm_dump_rsb_name(struct dlm_ls *ls, const char *name, int len);
+void dlm_print_lkb(struct dlm_lkb *lkb);
+void dlm_receive_message_saved(struct dlm_ls *ls, const struct dlm_message *ms,
+			       uint32_t saved_seq);
+void dlm_receive_buffer(const union dlm_packet *p, int nodeid);
+int dlm_modes_compat(int mode1, int mode2);
+void free_inactive_rsb(struct dlm_rsb *r);
+void dlm_put_rsb(struct dlm_rsb *r);
+void dlm_hold_rsb(struct dlm_rsb *r);
+int dlm_put_lkb(struct dlm_lkb *lkb);
+int dlm_lock_recovery_try(struct dlm_ls *ls);
+void dlm_lock_recovery(struct dlm_ls *ls);
+void dlm_unlock_recovery(struct dlm_ls *ls);
+void dlm_rsb_scan(struct timer_list *timer);
+void resume_scan_timer(struct dlm_ls *ls);
+
+int dlm_master_lookup(struct dlm_ls *ls, int from_nodeid, const char *name,
+		      int len, unsigned int flags, int *r_nodeid, int *result);
+
+int dlm_search_rsb_tree(struct rhashtable *rhash, const void *name, int len,
+			struct dlm_rsb **r_ret);
+
+void dlm_recover_purge(struct dlm_ls *ls, const struct list_head *root_list);
+void dlm_purge_mstcpy_locks(struct dlm_rsb *r);
+void dlm_recover_grant(struct dlm_ls *ls);
+int dlm_recover_waiters_post(struct dlm_ls *ls);
+void dlm_recover_waiters_pre(struct dlm_ls *ls);
+int dlm_recover_master_copy(struct dlm_ls *ls, const struct dlm_rcom *rc,
+			    __le32 *rl_remid, __le32 *rl_result);
+int dlm_recover_process_copy(struct dlm_ls *ls, const struct dlm_rcom *rc,
+			     uint64_t seq);
+
+int dlm_user_request(struct dlm_ls *ls, struct dlm_user_args *ua, int mode,
+	uint32_t flags, void *name, unsigned int namelen);
+int dlm_user_convert(struct dlm_ls *ls, struct dlm_user_args *ua_tmp,
+	int mode, uint32_t flags, uint32_t lkid, char *lvb_in);
+int dlm_user_adopt_orphan(struct dlm_ls *ls, struct dlm_user_args *ua_tmp,
+	int mode, uint32_t flags, void *name, unsigned int namelen,
+	uint32_t *lkid);
+int dlm_user_unlock(struct dlm_ls *ls, struct dlm_user_args *ua_tmp,
+	uint32_t flags, uint32_t lkid, char *lvb_in);
+int dlm_user_cancel(struct dlm_ls *ls,  struct dlm_user_args *ua_tmp,
+	uint32_t flags, uint32_t lkid);
+int dlm_user_purge(struct dlm_ls *ls, struct dlm_user_proc *proc,
+	int nodeid, int pid);
+int dlm_user_deadlock(struct dlm_ls *ls, uint32_t flags, uint32_t lkid);
+void dlm_clear_proc_locks(struct dlm_ls *ls, struct dlm_user_proc *proc);
+int dlm_debug_add_lkb(struct dlm_ls *ls, uint32_t lkb_id, char *name, int len,
+		      int lkb_nodeid, unsigned int lkb_flags, int lkb_status);
+int dlm_debug_add_lkb_to_waiters(struct dlm_ls *ls, uint32_t lkb_id,
+				 int mstype, int to_nodeid);
+
+static inline int is_master(struct dlm_rsb *r)
+{
+	WARN_ON_ONCE(r->res_nodeid == -1);
+
+	return !r->res_nodeid;
+}
+
+static inline void lock_rsb(struct dlm_rsb *r)
+{
+	spin_lock_bh(&r->res_lock);
+}
+
+static inline void unlock_rsb(struct dlm_rsb *r)
+{
+	spin_unlock_bh(&r->res_lock);
+}
+
+#endif
+