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, 52 insertions, 0 deletions

diff --git a/drivers/target/Kconfig b/drivers/target/Kconfig
new file mode 100644
index 000000000..92641d391
--- /dev/null
+++ b/drivers/target/Kconfig
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menuconfig TARGET_CORE
+	tristate "Generic Target Core Mod (TCM) and ConfigFS Infrastructure"
+	depends on BLOCK
+	select CONFIGFS_FS
+	select CRC_T10DIF
+	select SCSI_COMMON
+	select SGL_ALLOC
+	default n
+	help
+	Say Y or M here to enable the TCM Storage Engine and ConfigFS enabled
+	control path for target_core_mod.  This includes built-in TCM RAMDISK
+	subsystem logic for virtual LUN 0 access
+
+if TARGET_CORE
+
+config TCM_IBLOCK
+	tristate "TCM/IBLOCK Subsystem Plugin for Linux/BLOCK"
+	select BLK_DEV_INTEGRITY
+	help
+	Say Y here to enable the TCM/IBLOCK subsystem plugin for non-buffered
+	access to Linux/Block devices using BIO
+
+config TCM_FILEIO
+	tristate "TCM/FILEIO Subsystem Plugin for Linux/VFS"
+	help
+	Say Y here to enable the TCM/FILEIO subsystem plugin for buffered
+	access to Linux/VFS struct file or struct block_device
+
+config TCM_PSCSI
+	tristate "TCM/pSCSI Subsystem Plugin for Linux/SCSI"
+	depends on SCSI
+	help
+	Say Y here to enable the TCM/pSCSI subsystem plugin for non-buffered
+	passthrough access to Linux/SCSI device
+
+config TCM_USER2
+	tristate "TCM/USER Subsystem Plugin for Linux"
+	depends on UIO && NET
+	help
+	Say Y here to enable the TCM/USER subsystem plugin for a userspace
+	process to handle requests. This is version 2 of the ABI; version 1
+	is obsolete.
+
+source "drivers/target/loopback/Kconfig"
+source "drivers/target/tcm_fc/Kconfig"
+source "drivers/target/iscsi/Kconfig"
+source "drivers/target/sbp/Kconfig"
+source "drivers/target/tcm_remote/Kconfig"
+
+endif