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, 36 insertions, 0 deletions

diff --git a/fs/gfs2/Kconfig b/fs/gfs2/Kconfig
new file mode 100644
index 000000000..8beee571b
--- /dev/null
+++ b/fs/gfs2/Kconfig
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config GFS2_FS
+	tristate "GFS2 file system support"
+	select BUFFER_HEAD
+	select FS_POSIX_ACL
+	select CRC32
+	select QUOTACTL
+	select FS_IOMAP
+	help
+	  A cluster filesystem.
+
+	  Allows a cluster of computers to simultaneously use a block device
+	  that is shared between them (with FC, iSCSI, NBD, etc...).  GFS reads
+	  and writes to the block device like a local filesystem, but also uses
+	  a lock module to allow the computers coordinate their I/O so
+	  filesystem consistency is maintained.  One of the nifty features of
+	  GFS is perfect consistency -- changes made to the filesystem on one
+	  machine show up immediately on all other machines in the cluster.
+
+	  To use the GFS2 filesystem in a cluster, you will need to enable
+	  the locking module below. Documentation and utilities for GFS2 can
+	  be found here: http://sources.redhat.com/cluster
+
+	  The "nolock" lock module is now built in to GFS2 by default. If
+	  you want to use the DLM, be sure to enable IPv4/6 networking.
+
+config GFS2_FS_LOCKING_DLM
+	bool "GFS2 DLM locking"
+	depends on (GFS2_FS!=n) && NET && INET && \
+		CONFIGFS_FS && SYSFS && (DLM=y || DLM=GFS2_FS)
+	help
+	  Multiple node locking module for GFS2
+
+	  Most users of GFS2 will require this. It provides the locking
+	  interface between GFS2 and the DLM, which is required to use GFS2
+	  in a cluster environment.