From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- Documentation/ABI/testing/sysfs-driver-ppi | 75 ++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-driver-ppi (limited to 'Documentation/ABI/testing/sysfs-driver-ppi') diff --git a/Documentation/ABI/testing/sysfs-driver-ppi b/Documentation/ABI/testing/sysfs-driver-ppi new file mode 100644 index 000000000..1a56fc507 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-driver-ppi @@ -0,0 +1,75 @@ +What: /sys/class/tpm/tpmX/ppi/ +Date: August 2012 +KernelVersion: 3.6 +Contact: xiaoyan.zhang@intel.com +Description: + This folder includes the attributes related with PPI (Physical + Presence Interface). Only if TPM is supported by BIOS, this + folder makes sense. The folder path can be got by command + 'find /sys/ -name 'pcrs''. For the detail information of PPI, + please refer to the PPI specification from + + http://www.trustedcomputinggroup.org/ + + In Linux 4.2 ppi was moved to the character device directory. + A symlink from tpmX/device/ppi to tpmX/ppi to provide backwards + compatibility. + +What: /sys/class/tpm/tpmX/ppi/version +Date: August 2012 +Contact: xiaoyan.zhang@intel.com +Description: + This attribute shows the version of the PPI supported by the + platform. + This file is readonly. + +What: /sys/class/tpm/tpmX/ppi/request +Date: August 2012 +Contact: xiaoyan.zhang@intel.com +Description: + This attribute shows the request for an operation to be + executed in the pre-OS environment. It is the only input from + the OS to the pre-OS environment. The request should be an + integer value range from 1 to 160, and 0 means no request. + This file can be read and written. + +What: /sys/class/tpm/tpmX/ppi/response +Date: August 2012 +Contact: xiaoyan.zhang@intel.com +Description: + This attribute shows the response to the most recent operation + request it acted upon. The format is " + : ". + This file is readonly. + +What: /sys/class/tpm/tpmX/ppi/transition_action +Date: August 2012 +Contact: xiaoyan.zhang@intel.com +Description: + This attribute shows the platform-specific action that should + take place in order to transition to the BIOS for execution of + a requested operation. The format is ": ". + This file is readonly. + +What: /sys/class/tpm/tpmX/ppi/tcg_operations +Date: August 2012 +Contact: xiaoyan.zhang@intel.com +Description: + This attribute shows whether it is allowed to request an + operation to be executed in the pre-OS environment by the BIOS + for the requests defined by TCG, i.e. requests from 1 to 22. + The format is " : ". + This attribute is only supported by PPI version 1.2+. + This file is readonly. + +What: /sys/class/tpm/tpmX/ppi/vs_operations +Date: August 2012 +Contact: xiaoyan.zhang@intel.com +Description: + This attribute shows whether it is allowed to request an + operation to be executed in the pre-OS environment by the BIOS + for the verdor specific requests, i.e. requests from 128 to + 255. The format is same with tcg_operations. This attribute + is also only supported by PPI version 1.2+. + This file is readonly. -- cgit v1.3.1