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/input/joystick/magellan.c | 205 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 205 insertions(+) create mode 100644 drivers/input/joystick/magellan.c (limited to 'drivers/input/joystick/magellan.c') diff --git a/drivers/input/joystick/magellan.c b/drivers/input/joystick/magellan.c new file mode 100644 index 000000000..201a049c8 --- /dev/null +++ b/drivers/input/joystick/magellan.c @@ -0,0 +1,205 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 1999-2001 Vojtech Pavlik + */ + +/* + * Magellan and Space Mouse 6dof controller driver for Linux + */ + +#include +#include +#include +#include +#include + +#define DRIVER_DESC "Magellan and SpaceMouse 6dof controller driver" + +MODULE_AUTHOR("Vojtech Pavlik "); +MODULE_DESCRIPTION(DRIVER_DESC); +MODULE_LICENSE("GPL"); + +/* + * Definitions & global arrays. + */ + +#define MAGELLAN_MAX_LENGTH 32 + +static int magellan_buttons[] = { BTN_0, BTN_1, BTN_2, BTN_3, BTN_4, BTN_5, BTN_6, BTN_7, BTN_8 }; +static int magellan_axes[] = { ABS_X, ABS_Y, ABS_Z, ABS_RX, ABS_RY, ABS_RZ }; + +/* + * Per-Magellan data. + */ + +struct magellan { + struct input_dev *dev; + int idx; + unsigned char data[MAGELLAN_MAX_LENGTH]; + char phys[32]; +}; + +/* + * magellan_crunch_nibbles() verifies that the bytes sent from the Magellan + * have correct upper nibbles for the lower ones, if not, the packet will + * be thrown away. It also strips these upper halves to simplify further + * processing. + */ + +static int magellan_crunch_nibbles(unsigned char *data, int count) +{ + static const unsigned char nibbles[16] __nonstring = "0AB3D56GH9:Kdev; + unsigned char *data = magellan->data; + int i, t; + + if (!magellan->idx) return; + + switch (magellan->data[0]) { + + case 'd': /* Axis data */ + if (magellan->idx != 25) return; + if (magellan_crunch_nibbles(data, 24)) return; + for (i = 0; i < 6; i++) + input_report_abs(dev, magellan_axes[i], + (data[(i << 2) + 1] << 12 | data[(i << 2) + 2] << 8 | + data[(i << 2) + 3] << 4 | data[(i << 2) + 4]) - 32768); + break; + + case 'k': /* Button data */ + if (magellan->idx != 4) return; + if (magellan_crunch_nibbles(data, 3)) return; + t = (data[1] << 1) | (data[2] << 5) | data[3]; + for (i = 0; i < 9; i++) input_report_key(dev, magellan_buttons[i], (t >> i) & 1); + break; + } + + input_sync(dev); +} + +static irqreturn_t magellan_interrupt(struct serio *serio, + unsigned char data, unsigned int flags) +{ + struct magellan* magellan = serio_get_drvdata(serio); + + if (data == '\r') { + magellan_process_packet(magellan); + magellan->idx = 0; + } else { + if (magellan->idx < MAGELLAN_MAX_LENGTH) + magellan->data[magellan->idx++] = data; + } + return IRQ_HANDLED; +} + +/* + * magellan_disconnect() is the opposite of magellan_connect() + */ + +static void magellan_disconnect(struct serio *serio) +{ + struct magellan* magellan = serio_get_drvdata(serio); + + serio_close(serio); + serio_set_drvdata(serio, NULL); + input_unregister_device(magellan->dev); + kfree(magellan); +} + +/* + * magellan_connect() is the routine that is called when someone adds a + * new serio device that supports Magellan protocol and registers it as + * an input device. + */ + +static int magellan_connect(struct serio *serio, struct serio_driver *drv) +{ + struct magellan *magellan; + struct input_dev *input_dev; + int err = -ENOMEM; + int i; + + magellan = kzalloc_obj(*magellan); + input_dev = input_allocate_device(); + if (!magellan || !input_dev) + goto fail1; + + magellan->dev = input_dev; + snprintf(magellan->phys, sizeof(magellan->phys), "%s/input0", serio->phys); + + input_dev->name = "LogiCad3D Magellan / SpaceMouse"; + input_dev->phys = magellan->phys; + input_dev->id.bustype = BUS_RS232; + input_dev->id.vendor = SERIO_MAGELLAN; + input_dev->id.product = 0x0001; + input_dev->id.version = 0x0100; + input_dev->dev.parent = &serio->dev; + + input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS); + + for (i = 0; i < 9; i++) + set_bit(magellan_buttons[i], input_dev->keybit); + + for (i = 0; i < 6; i++) + input_set_abs_params(input_dev, magellan_axes[i], -360, 360, 0, 0); + + serio_set_drvdata(serio, magellan); + + err = serio_open(serio, drv); + if (err) + goto fail2; + + err = input_register_device(magellan->dev); + if (err) + goto fail3; + + return 0; + + fail3: serio_close(serio); + fail2: serio_set_drvdata(serio, NULL); + fail1: input_free_device(input_dev); + kfree(magellan); + return err; +} + +/* + * The serio driver structure. + */ + +static const struct serio_device_id magellan_serio_ids[] = { + { + .type = SERIO_RS232, + .proto = SERIO_MAGELLAN, + .id = SERIO_ANY, + .extra = SERIO_ANY, + }, + { 0 } +}; + +MODULE_DEVICE_TABLE(serio, magellan_serio_ids); + +static struct serio_driver magellan_drv = { + .driver = { + .name = "magellan", + }, + .description = DRIVER_DESC, + .id_table = magellan_serio_ids, + .interrupt = magellan_interrupt, + .connect = magellan_connect, + .disconnect = magellan_disconnect, +}; + +module_serio_driver(magellan_drv); -- cgit v1.3.1