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, 31 insertions, 0 deletions

diff --git a/fs/ntfs/ea.h b/fs/ntfs/ea.h
new file mode 100644
index 000000000..acb39c2a6
--- /dev/null
+++ b/fs/ntfs/ea.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _LINUX_NTFS_EA_H
+#define _LINUX_NTFS_EA_H
+
+#define NTFS_EA_UID	BIT(1)
+#define NTFS_EA_GID	BIT(2)
+#define NTFS_EA_MODE	BIT(3)
+
+extern const struct xattr_handler *const ntfs_xattr_handlers[];
+
+int ntfs_ea_set_wsl_not_symlink(struct ntfs_inode *ni, mode_t mode, dev_t dev);
+int ntfs_ea_get_wsl_inode(struct inode *inode, dev_t *rdevp, unsigned int flags,
+			  bool *has_lxmod);
+int ntfs_ea_set_wsl_inode(struct inode *inode, dev_t rdev, __le16 *ea_size,
+		unsigned int flags);
+ssize_t ntfs_listxattr(struct dentry *dentry, char *buffer, size_t size);
+
+#ifdef CONFIG_NTFS_FS_POSIX_ACL
+struct posix_acl *ntfs_get_acl(struct mnt_idmap *idmap, struct dentry *dentry,
+			       int type);
+int ntfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
+		 struct posix_acl *acl, int type);
+int ntfs_init_acl(struct mnt_idmap *idmap, struct inode *inode,
+		  struct inode *dir);
+#else
+#define ntfs_get_acl NULL
+#define ntfs_set_acl NULL
+#endif
+
+#endif /* _LINUX_NTFS_EA_H */