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/cdx/controller/mcdid.h | 63 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 drivers/cdx/controller/mcdid.h (limited to 'drivers/cdx/controller/mcdid.h') diff --git a/drivers/cdx/controller/mcdid.h b/drivers/cdx/controller/mcdid.h new file mode 100644 index 000000000..7fc29f099 --- /dev/null +++ b/drivers/cdx/controller/mcdid.h @@ -0,0 +1,63 @@ +/* SPDX-License-Identifier: GPL-2.0 + * + * Copyright 2008-2013 Solarflare Communications Inc. + * Copyright (C) 2022-2025, Advanced Micro Devices, Inc. + */ + +#ifndef CDX_MCDID_H +#define CDX_MCDID_H + +#include +#include +#include + +#include "mc_cdx_pcol.h" + +#ifdef DEBUG +#define CDX_WARN_ON_ONCE_PARANOID(x) WARN_ON_ONCE(x) +#define CDX_WARN_ON_PARANOID(x) WARN_ON(x) +#else +#define CDX_WARN_ON_ONCE_PARANOID(x) do {} while (0) +#define CDX_WARN_ON_PARANOID(x) do {} while (0) +#endif + +#define MCDI_BUF_LEN (8 + MCDI_CTL_SDU_LEN_MAX) + +static inline struct cdx_mcdi_iface *cdx_mcdi_if(struct cdx_mcdi *cdx) +{ + return cdx->mcdi ? &cdx->mcdi->iface : NULL; +} + +int cdx_mcdi_rpc_async(struct cdx_mcdi *cdx, unsigned int cmd, + const struct cdx_dword *inbuf, size_t inlen, + cdx_mcdi_async_completer *complete, + unsigned long cookie); +int cdx_mcdi_wait_for_quiescence(struct cdx_mcdi *cdx, + unsigned int timeout_jiffies); + +/* + * We expect that 16- and 32-bit fields in MCDI requests and responses + * are appropriately aligned, but 64-bit fields are only + * 32-bit-aligned. + */ +#define MCDI_BYTE(_buf, _field) \ + ((void)BUILD_BUG_ON_ZERO(MC_CMD_ ## _field ## _LEN != 1), \ + *MCDI_PTR(_buf, _field)) +#define MCDI_WORD(_buf, _field) \ + ((void)BUILD_BUG_ON_ZERO(MC_CMD_ ## _field ## _LEN != 2), \ + le16_to_cpu(*(__force const __le16 *)MCDI_PTR(_buf, _field))) +#define MCDI_POPULATE_DWORD_1(_buf, _field, _name1, _value1) \ + CDX_POPULATE_DWORD_1(*_MCDI_DWORD(_buf, _field), \ + MC_CMD_ ## _name1, _value1) +#define MCDI_SET_QWORD(_buf, _field, _value) \ + do { \ + CDX_POPULATE_DWORD_1(_MCDI_DWORD(_buf, _field)[0], \ + CDX_DWORD, (u32)(_value)); \ + CDX_POPULATE_DWORD_1(_MCDI_DWORD(_buf, _field)[1], \ + CDX_DWORD, (u64)(_value) >> 32); \ + } while (0) +#define MCDI_QWORD(_buf, _field) \ + (CDX_DWORD_FIELD(_MCDI_DWORD(_buf, _field)[0], CDX_DWORD) | \ + (u64)CDX_DWORD_FIELD(_MCDI_DWORD(_buf, _field)[1], CDX_DWORD) << 32) + +#endif /* CDX_MCDID_H */ -- cgit v1.3.1