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/mcb/mcb-lpc.c | 187 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 187 insertions(+) create mode 100644 drivers/mcb/mcb-lpc.c (limited to 'drivers/mcb/mcb-lpc.c') diff --git a/drivers/mcb/mcb-lpc.c b/drivers/mcb/mcb-lpc.c new file mode 100644 index 000000000..070aa787a --- /dev/null +++ b/drivers/mcb/mcb-lpc.c @@ -0,0 +1,187 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * MEN Chameleon Bus. + * + * Copyright (C) 2014 MEN Mikroelektronik GmbH (www.men.de) + * Author: Andreas Werner + */ + +#include +#include +#include +#include +#include +#include "mcb-internal.h" + +struct priv { + struct mcb_bus *bus; + struct resource *mem; + void __iomem *base; +}; + +static int mcb_lpc_probe(struct platform_device *pdev) +{ + struct resource *res; + struct priv *priv; + int ret = 0, table_size; + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!priv->mem) { + dev_err(&pdev->dev, "No Memory resource\n"); + return -ENODEV; + } + + res = devm_request_mem_region(&pdev->dev, priv->mem->start, + resource_size(priv->mem), + KBUILD_MODNAME); + if (!res) { + dev_err(&pdev->dev, "Failed to request IO memory\n"); + return -EBUSY; + } + + priv->base = devm_ioremap(&pdev->dev, priv->mem->start, + resource_size(priv->mem)); + if (!priv->base) { + dev_err(&pdev->dev, "Cannot ioremap\n"); + return -ENOMEM; + } + + platform_set_drvdata(pdev, priv); + + priv->bus = mcb_alloc_bus(&pdev->dev); + if (IS_ERR(priv->bus)) + return PTR_ERR(priv->bus); + + ret = chameleon_parse_cells(priv->bus, priv->mem->start, priv->base); + if (ret < 0) { + goto out_mcb_bus; + } + + table_size = ret; + + if (table_size < CHAM_HEADER_SIZE) { + /* Release the previous resources */ + devm_iounmap(&pdev->dev, priv->base); + devm_release_mem_region(&pdev->dev, priv->mem->start, resource_size(priv->mem)); + + /* Then, allocate it again with the actual chameleon table size */ + res = devm_request_mem_region(&pdev->dev, priv->mem->start, + table_size, + KBUILD_MODNAME); + if (!res) { + dev_err(&pdev->dev, "Failed to request PCI memory\n"); + ret = -EBUSY; + goto out_mcb_bus; + } + + priv->base = devm_ioremap(&pdev->dev, priv->mem->start, table_size); + if (!priv->base) { + dev_err(&pdev->dev, "Cannot ioremap\n"); + ret = -ENOMEM; + goto out_mcb_bus; + } + + platform_set_drvdata(pdev, priv); + } + + mcb_bus_add_devices(priv->bus); + + return 0; + +out_mcb_bus: + mcb_release_bus(priv->bus); + return ret; +} + +static void mcb_lpc_remove(struct platform_device *pdev) +{ + struct priv *priv = platform_get_drvdata(pdev); + + mcb_release_bus(priv->bus); +} + +static struct platform_device *mcb_lpc_pdev; + +static int mcb_lpc_create_platform_device(const struct dmi_system_id *id) +{ + struct resource *res = id->driver_data; + int ret; + + mcb_lpc_pdev = platform_device_alloc("mcb-lpc", -1); + if (!mcb_lpc_pdev) + return -ENOMEM; + + ret = platform_device_add_resources(mcb_lpc_pdev, res, 1); + if (ret) + goto out_put; + + ret = platform_device_add(mcb_lpc_pdev); + if (ret) + goto out_put; + + return 0; + +out_put: + platform_device_put(mcb_lpc_pdev); + return ret; +} + +static struct resource sc24_fpga_resource = DEFINE_RES_MEM(0xe000e000, CHAM_HEADER_SIZE); +static struct resource sc31_fpga_resource = DEFINE_RES_MEM(0xf000e000, CHAM_HEADER_SIZE); + +static struct platform_driver mcb_lpc_driver = { + .driver = { + .name = "mcb-lpc", + }, + .probe = mcb_lpc_probe, + .remove = mcb_lpc_remove, +}; + +static const struct dmi_system_id mcb_lpc_dmi_table[] = { + { + .ident = "SC24", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "MEN"), + DMI_MATCH(DMI_PRODUCT_VERSION, "14SC24"), + }, + .driver_data = (void *)&sc24_fpga_resource, + .callback = mcb_lpc_create_platform_device, + }, + { + .ident = "SC31", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "MEN"), + DMI_MATCH(DMI_PRODUCT_VERSION, "14SC31"), + }, + .driver_data = (void *)&sc31_fpga_resource, + .callback = mcb_lpc_create_platform_device, + }, + {} +}; +MODULE_DEVICE_TABLE(dmi, mcb_lpc_dmi_table); + +static int __init mcb_lpc_init(void) +{ + if (!dmi_check_system(mcb_lpc_dmi_table)) + return -ENODEV; + + return platform_driver_register(&mcb_lpc_driver); +} + +static void __exit mcb_lpc_exit(void) +{ + platform_device_unregister(mcb_lpc_pdev); + platform_driver_unregister(&mcb_lpc_driver); +} + +module_init(mcb_lpc_init); +module_exit(mcb_lpc_exit); + +MODULE_AUTHOR("Andreas Werner "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("MCB over LPC support"); +MODULE_IMPORT_NS("MCB"); -- cgit v1.3.1