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, 66 insertions, 0 deletions

diff --git a/fs/gfs2/super.h b/fs/gfs2/super.h
new file mode 100644
index 000000000..173f1e74c
--- /dev/null
+++ b/fs/gfs2/super.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
+ * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
+ */
+
+#ifndef __SUPER_DOT_H__
+#define __SUPER_DOT_H__
+
+#include <linux/fs.h>
+#include <linux/dcache.h>
+#include "incore.h"
+
+/* Supported fs format version range */
+#define GFS2_FS_FORMAT_MIN (1801)
+#define GFS2_FS_FORMAT_MAX (1802)
+
+void gfs2_lm_unmount(struct gfs2_sbd *sdp);
+
+static inline unsigned int gfs2_jindex_size(struct gfs2_sbd *sdp)
+{
+	unsigned int x;
+	spin_lock(&sdp->sd_jindex_spin);
+	x = sdp->sd_journals;
+	spin_unlock(&sdp->sd_jindex_spin);
+	return x;
+}
+
+void gfs2_jindex_free(struct gfs2_sbd *sdp);
+
+struct gfs2_jdesc *gfs2_jdesc_find(struct gfs2_sbd *sdp, unsigned int jid);
+int gfs2_jdesc_check(struct gfs2_jdesc *jd);
+int gfs2_lookup_in_master_dir(struct gfs2_sbd *sdp, char *filename,
+			      struct gfs2_inode **ipp);
+
+int gfs2_make_fs_rw(struct gfs2_sbd *sdp);
+void gfs2_make_fs_ro(struct gfs2_sbd *sdp);
+void gfs2_online_uevent(struct gfs2_sbd *sdp);
+void gfs2_destroy_threads(struct gfs2_sbd *sdp);
+int gfs2_statfs_init(struct gfs2_sbd *sdp);
+void gfs2_statfs_change(struct gfs2_sbd *sdp, s64 total, s64 free,
+		        s64 dinodes);
+void gfs2_statfs_change_in(struct gfs2_statfs_change_host *sc,
+			   const void *buf);
+void gfs2_statfs_change_out(const struct gfs2_statfs_change_host *sc,
+			    void *buf);
+void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh);
+int gfs2_statfs_sync(struct super_block *sb, int type);
+void gfs2_freeze_func(struct work_struct *work);
+
+void free_local_statfs_inodes(struct gfs2_sbd *sdp);
+struct inode *find_local_statfs_inode(struct gfs2_sbd *sdp,
+				      unsigned int index);
+void free_sbd(struct gfs2_sbd *sdp);
+
+extern struct file_system_type gfs2_fs_type;
+extern struct file_system_type gfs2meta_fs_type;
+extern const struct export_operations gfs2_export_ops;
+extern const struct super_operations gfs2_super_ops;
+extern const struct dentry_operations gfs2_dops;
+
+extern const struct xattr_handler * const gfs2_xattr_handlers_max[];
+extern const struct xattr_handler * const *gfs2_xattr_handlers_min;
+
+#endif /* __SUPER_DOT_H__ */
+