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/base/isa.c | 181 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 181 insertions(+) create mode 100644 drivers/base/isa.c (limited to 'drivers/base/isa.c') diff --git a/drivers/base/isa.c b/drivers/base/isa.c new file mode 100644 index 000000000..4e9f68080 --- /dev/null +++ b/drivers/base/isa.c @@ -0,0 +1,181 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * ISA bus. + */ + +#include +#include +#include +#include +#include +#include +#include + +static struct device *isa_bus; + +struct isa_dev { + struct device dev; + struct device *next; + unsigned int id; +}; + +#define to_isa_dev(x) container_of((x), struct isa_dev, dev) + +static int isa_bus_match(struct device *dev, const struct device_driver *driver) +{ + struct isa_driver *isa_driver = to_isa_driver(driver); + + if (dev->platform_data == isa_driver) { + if (!isa_driver->match || + isa_driver->match(dev, to_isa_dev(dev)->id)) + return 1; + dev->platform_data = NULL; + } + return 0; +} + +static int isa_bus_probe(struct device *dev) +{ + struct isa_driver *isa_driver = dev->platform_data; + + if (isa_driver && isa_driver->probe) + return isa_driver->probe(dev, to_isa_dev(dev)->id); + + return 0; +} + +static void isa_bus_remove(struct device *dev) +{ + struct isa_driver *isa_driver = dev->platform_data; + + if (isa_driver && isa_driver->remove) + isa_driver->remove(dev, to_isa_dev(dev)->id); +} + +static void isa_bus_shutdown(struct device *dev) +{ + struct isa_driver *isa_driver = dev->platform_data; + + if (isa_driver && isa_driver->shutdown) + isa_driver->shutdown(dev, to_isa_dev(dev)->id); +} + +static int isa_bus_suspend(struct device *dev, pm_message_t state) +{ + struct isa_driver *isa_driver = dev->platform_data; + + if (isa_driver && isa_driver->suspend) + return isa_driver->suspend(dev, to_isa_dev(dev)->id, state); + + return 0; +} + +static int isa_bus_resume(struct device *dev) +{ + struct isa_driver *isa_driver = dev->platform_data; + + if (isa_driver && isa_driver->resume) + return isa_driver->resume(dev, to_isa_dev(dev)->id); + + return 0; +} + +static const struct bus_type isa_bus_type = { + .name = "isa", + .match = isa_bus_match, + .probe = isa_bus_probe, + .remove = isa_bus_remove, + .shutdown = isa_bus_shutdown, + .suspend = isa_bus_suspend, + .resume = isa_bus_resume +}; + +static void isa_dev_release(struct device *dev) +{ + kfree(to_isa_dev(dev)); +} + +void isa_unregister_driver(struct isa_driver *isa_driver) +{ + struct device *dev = isa_driver->devices; + + while (dev) { + struct device *tmp = to_isa_dev(dev)->next; + device_unregister(dev); + dev = tmp; + } + driver_unregister(&isa_driver->driver); +} +EXPORT_SYMBOL_GPL(isa_unregister_driver); + +int isa_register_driver(struct isa_driver *isa_driver, unsigned int ndev) +{ + int error; + unsigned int id; + + isa_driver->driver.bus = &isa_bus_type; + isa_driver->devices = NULL; + + error = driver_register(&isa_driver->driver); + if (error) + return error; + + for (id = 0; id < ndev; id++) { + struct isa_dev *isa_dev; + + isa_dev = kzalloc_obj(*isa_dev); + if (!isa_dev) { + error = -ENOMEM; + break; + } + + isa_dev->dev.parent = isa_bus; + isa_dev->dev.bus = &isa_bus_type; + + dev_set_name(&isa_dev->dev, "%s.%u", + isa_driver->driver.name, id); + isa_dev->dev.platform_data = isa_driver; + isa_dev->dev.release = isa_dev_release; + isa_dev->id = id; + + isa_dev->dev.coherent_dma_mask = DMA_BIT_MASK(24); + isa_dev->dev.dma_mask = &isa_dev->dev.coherent_dma_mask; + + error = device_register(&isa_dev->dev); + if (error) { + put_device(&isa_dev->dev); + break; + } + + isa_dev->next = isa_driver->devices; + isa_driver->devices = &isa_dev->dev; + } + + if (!error && !isa_driver->devices) + error = -ENODEV; + + if (error) + isa_unregister_driver(isa_driver); + + return error; +} +EXPORT_SYMBOL_GPL(isa_register_driver); + +static int __init isa_bus_init(void) +{ + int error; + + error = bus_register(&isa_bus_type); + if (error) + return error; + + isa_bus = root_device_register("isa"); + if (IS_ERR(isa_bus)) { + bus_unregister(&isa_bus_type); + return PTR_ERR(isa_bus); + } + + return 0; +} + +postcore_initcall(isa_bus_init); -- cgit v1.3.1