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, 33 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-ibft b/Documentation/ABI/testing/sysfs-ibft
new file mode 100644
index 000000000..7d6725fe6
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-ibft
@@ -0,0 +1,33 @@
+What:		/sys/firmware/ibft/initiator
+Date:		November 2007
+Contact:	Konrad Rzeszutek <ketuzsezr@darnok.org>
+Description:	The /sys/firmware/ibft/initiator directory will contain
+		files that expose the iSCSI Boot Firmware Table initiator data.
+		Usually this contains the Initiator name.
+
+What:		/sys/firmware/ibft/targetX
+Date:		November 2007
+Contact:	Konrad Rzeszutek <ketuzsezr@darnok.org>
+Description:	The /sys/firmware/ibft/targetX directory will contain
+		files that expose the iSCSI Boot Firmware Table target data.
+		Usually this contains the target's IP address, boot LUN,
+		target name, and what NIC it is associated with. It can also
+		contain the CHAP name (and password), the reverse CHAP
+		name (and password)
+
+What:		/sys/firmware/ibft/ethernetX
+Date:		November 2007
+Contact:	Konrad Rzeszutek <ketuzsezr@darnok.org>
+Description:	The /sys/firmware/ibft/ethernetX directory will contain
+		files that expose the iSCSI Boot Firmware Table NIC data.
+		Usually this contains the IP address, MAC, and gateway of the NIC.
+
+What:		/sys/firmware/ibft/acpi_header
+Date:		March 2016
+Contact:	David Bond <dbond@suse.com>
+Description:	The /sys/firmware/ibft/acpi_header directory will contain files
+		that expose the SIGNATURE, OEM_ID, and OEM_TABLE_ID fields of the
+		acpi table header of the iBFT structure.  This will allow for
+		identification of the creator of the table which is useful in
+		determining quirks associated with some adapters when used in
+		hardware vs software iscsi initiator mode.