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 --- drivers/crypto/ccp/sev-dev.h | 89 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 drivers/crypto/ccp/sev-dev.h (limited to 'drivers/crypto/ccp/sev-dev.h') diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h new file mode 100644 index 000000000..d5e596606 --- /dev/null +++ b/drivers/crypto/ccp/sev-dev.h @@ -0,0 +1,89 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * AMD Platform Security Processor (PSP) interface driver + * + * Copyright (C) 2017-2019 Advanced Micro Devices, Inc. + * + * Author: Brijesh Singh + */ + +#ifndef __SEV_DEV_H__ +#define __SEV_DEV_H__ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define SEV_CMDRESP_CMD GENMASK(26, 16) +#define SEV_CMD_COMPLETE BIT(1) +#define SEV_CMDRESP_IOC BIT(0) + +struct sev_misc_dev { + struct kref refcount; + struct miscdevice misc; +}; + +struct sev_tio_status; + +struct sev_device { + struct device *dev; + struct psp_device *psp; + + void __iomem *io_regs; + + struct sev_vdata *vdata; + + unsigned int int_rcvd; + wait_queue_head_t int_queue; + struct sev_misc_dev *misc; + + u8 api_major; + u8 api_minor; + u8 build; + + void *cmd_buf; + void *cmd_buf_backup; + bool cmd_buf_active; + bool cmd_buf_backup_active; + + bool snp_initialized; + + struct kobject *sev_kobj; + struct kobject *verify_mit; + + struct sev_user_data_status sev_plat_status; + + struct sev_user_data_snp_status snp_plat_status; + struct snp_feature_info snp_feat_info_0; + + struct tsm_dev *tsmdev; + struct sev_tio_status *tio_status; +}; + +int sev_dev_init(struct psp_device *psp); +void sev_dev_destroy(struct psp_device *psp); + +int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret); + +void sev_pci_init(void); +void sev_pci_exit(void); + +struct page *snp_alloc_hv_fixed_pages(unsigned int num_2mb_pages); +void snp_free_hv_fixed_pages(struct page *page); + +void sev_tsm_init_locked(struct sev_device *sev, void *tio_status_page); +void sev_tsm_uninit(struct sev_device *sev); +int sev_tio_cmd_buffer_len(int cmd); + +#endif /* __SEV_DEV_H */ -- cgit v1.3.1