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/input-mt.c | 534 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 534 insertions(+) create mode 100644 drivers/input/input-mt.c (limited to 'drivers/input/input-mt.c') diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c new file mode 100644 index 000000000..c06e98fbd --- /dev/null +++ b/drivers/input/input-mt.c @@ -0,0 +1,534 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Input Multitouch Library + * + * Copyright (c) 2008-2010 Henrik Rydberg + */ + +#include +#include +#include +#include "input-core-private.h" + +#define TRKID_SGN ((TRKID_MAX + 1) >> 1) + +static void copy_abs(struct input_dev *dev, unsigned int dst, unsigned int src) +{ + if (dev->absinfo && test_bit(src, dev->absbit)) { + dev->absinfo[dst] = dev->absinfo[src]; + dev->absinfo[dst].fuzz = 0; + __set_bit(dst, dev->absbit); + } +} + +/** + * input_mt_init_slots() - initialize MT input slots + * @dev: input device supporting MT events and finger tracking + * @num_slots: number of slots used by the device + * @flags: mt tasks to handle in core + * + * This function allocates all necessary memory for MT slot handling + * in the input device, prepares the ABS_MT_SLOT and + * ABS_MT_TRACKING_ID events for use and sets up appropriate buffers. + * Depending on the flags set, it also performs pointer emulation and + * frame synchronization. + * + * May be called repeatedly. Returns -EINVAL if attempting to + * reinitialize with a different number of slots. + */ +int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots, + unsigned int flags) +{ + if (!num_slots) + return 0; + + if (dev->mt) + return dev->mt->num_slots != num_slots ? -EINVAL : 0; + + /* Arbitrary limit for avoiding too large memory allocation. */ + if (num_slots > 1024) + return -EINVAL; + + struct input_mt *mt __free(kfree) = + kzalloc_flex(*mt, slots, num_slots); + if (!mt) + return -ENOMEM; + + mt->num_slots = num_slots; + mt->flags = flags; + input_set_abs_params(dev, ABS_MT_SLOT, 0, num_slots - 1, 0, 0); + input_set_abs_params(dev, ABS_MT_TRACKING_ID, 0, TRKID_MAX, 0, 0); + + if (flags & (INPUT_MT_POINTER | INPUT_MT_DIRECT)) { + __set_bit(EV_KEY, dev->evbit); + __set_bit(BTN_TOUCH, dev->keybit); + + copy_abs(dev, ABS_X, ABS_MT_POSITION_X); + copy_abs(dev, ABS_Y, ABS_MT_POSITION_Y); + copy_abs(dev, ABS_PRESSURE, ABS_MT_PRESSURE); + } + if (flags & INPUT_MT_POINTER) { + __set_bit(BTN_TOOL_FINGER, dev->keybit); + __set_bit(BTN_TOOL_DOUBLETAP, dev->keybit); + if (num_slots >= 3) + __set_bit(BTN_TOOL_TRIPLETAP, dev->keybit); + if (num_slots >= 4) + __set_bit(BTN_TOOL_QUADTAP, dev->keybit); + if (num_slots >= 5) + __set_bit(BTN_TOOL_QUINTTAP, dev->keybit); + __set_bit(INPUT_PROP_POINTER, dev->propbit); + } + if (flags & INPUT_MT_DIRECT) + __set_bit(INPUT_PROP_DIRECT, dev->propbit); + if (flags & INPUT_MT_SEMI_MT) + __set_bit(INPUT_PROP_SEMI_MT, dev->propbit); + if (flags & INPUT_MT_TRACK) { + unsigned int n2 = num_slots * num_slots; + mt->red = kzalloc_objs(*mt->red, n2); + if (!mt->red) + return -ENOMEM; + } + + /* Mark slots as 'inactive' */ + for (unsigned int i = 0; i < num_slots; i++) + input_mt_set_value(&mt->slots[i], ABS_MT_TRACKING_ID, -1); + + /* Mark slots as 'unused' */ + mt->frame = 1; + + dev->mt = no_free_ptr(mt); + return 0; +} +EXPORT_SYMBOL(input_mt_init_slots); + +/** + * input_mt_destroy_slots() - frees the MT slots of the input device + * @dev: input device with allocated MT slots + * + * This function is only needed in error path as the input core will + * automatically free the MT slots when the device is destroyed. + */ +void input_mt_destroy_slots(struct input_dev *dev) +{ + if (dev->mt) { + kfree(dev->mt->red); + kfree(dev->mt); + } + dev->mt = NULL; +} +EXPORT_SYMBOL(input_mt_destroy_slots); + +/** + * input_mt_report_slot_state() - report contact state + * @dev: input device with allocated MT slots + * @tool_type: the tool type to use in this slot + * @active: true if contact is active, false otherwise + * + * Reports a contact via ABS_MT_TRACKING_ID, and optionally + * ABS_MT_TOOL_TYPE. If active is true and the slot is currently + * inactive, or if the tool type is changed, a new tracking id is + * assigned to the slot. The tool type is only reported if the + * corresponding absbit field is set. + * + * Returns true if contact is active. + */ +bool input_mt_report_slot_state(struct input_dev *dev, + unsigned int tool_type, bool active) +{ + struct input_mt *mt = dev->mt; + struct input_mt_slot *slot; + int id; + + if (!mt) + return false; + + slot = &mt->slots[mt->slot]; + slot->frame = mt->frame; + + if (!active) { + input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1); + return false; + } + + id = input_mt_get_value(slot, ABS_MT_TRACKING_ID); + if (id < 0) + id = input_mt_new_trkid(mt); + + input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, id); + input_event(dev, EV_ABS, ABS_MT_TOOL_TYPE, tool_type); + + return true; +} +EXPORT_SYMBOL(input_mt_report_slot_state); + +/** + * input_mt_report_finger_count() - report contact count + * @dev: input device with allocated MT slots + * @count: the number of contacts + * + * Reports the contact count via BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP, + * BTN_TOOL_TRIPLETAP and BTN_TOOL_QUADTAP. + * + * The input core ensures only the KEY events already setup for + * this device will produce output. + */ +void input_mt_report_finger_count(struct input_dev *dev, int count) +{ + input_event(dev, EV_KEY, BTN_TOOL_FINGER, count == 1); + input_event(dev, EV_KEY, BTN_TOOL_DOUBLETAP, count == 2); + input_event(dev, EV_KEY, BTN_TOOL_TRIPLETAP, count == 3); + input_event(dev, EV_KEY, BTN_TOOL_QUADTAP, count == 4); + input_event(dev, EV_KEY, BTN_TOOL_QUINTTAP, count == 5); +} +EXPORT_SYMBOL(input_mt_report_finger_count); + +/** + * input_mt_report_pointer_emulation() - common pointer emulation + * @dev: input device with allocated MT slots + * @use_count: report number of active contacts as finger count + * + * Performs legacy pointer emulation via BTN_TOUCH, ABS_X, ABS_Y and + * ABS_PRESSURE. Touchpad finger count is emulated if use_count is true. + * + * The input core ensures only the KEY and ABS axes already setup for + * this device will produce output. + */ +void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count) +{ + struct input_mt *mt = dev->mt; + struct input_mt_slot *oldest; + int oldid, count, i; + int p, reported_p = 0; + + if (!mt) + return; + + oldest = NULL; + oldid = mt->trkid; + count = 0; + + for (i = 0; i < mt->num_slots; ++i) { + struct input_mt_slot *ps = &mt->slots[i]; + int id = input_mt_get_value(ps, ABS_MT_TRACKING_ID); + + if (id < 0) + continue; + if ((id - oldid) & TRKID_SGN) { + oldest = ps; + oldid = id; + } + if (test_bit(ABS_MT_PRESSURE, dev->absbit)) { + p = input_mt_get_value(ps, ABS_MT_PRESSURE); + if (mt->flags & INPUT_MT_TOTAL_FORCE) + reported_p += p; + else if (oldid == id) + reported_p = p; + } + count++; + } + + input_event(dev, EV_KEY, BTN_TOUCH, count > 0); + + if (use_count) { + if (count == 0 && + !test_bit(ABS_MT_DISTANCE, dev->absbit) && + test_bit(ABS_DISTANCE, dev->absbit) && + input_abs_get_val(dev, ABS_DISTANCE) != 0) { + /* + * Force reporting BTN_TOOL_FINGER for devices that + * only report general hover (and not per-contact + * distance) when contact is in proximity but not + * on the surface. + */ + count = 1; + } + + input_mt_report_finger_count(dev, count); + } + + if (oldest) { + int x = input_mt_get_value(oldest, ABS_MT_POSITION_X); + int y = input_mt_get_value(oldest, ABS_MT_POSITION_Y); + + input_event(dev, EV_ABS, ABS_X, x); + input_event(dev, EV_ABS, ABS_Y, y); + + if (test_bit(ABS_MT_PRESSURE, dev->absbit)) + input_event(dev, EV_ABS, ABS_PRESSURE, reported_p); + } else { + if (test_bit(ABS_MT_PRESSURE, dev->absbit)) + input_event(dev, EV_ABS, ABS_PRESSURE, 0); + } +} +EXPORT_SYMBOL(input_mt_report_pointer_emulation); + +static void __input_mt_drop_unused(struct input_dev *dev, struct input_mt *mt) +{ + int i; + + lockdep_assert_held(&dev->event_lock); + + for (i = 0; i < mt->num_slots; i++) { + if (input_mt_is_active(&mt->slots[i]) && + !input_mt_is_used(mt, &mt->slots[i])) { + input_handle_event(dev, EV_ABS, ABS_MT_SLOT, i); + input_handle_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1); + } + } +} + +/** + * input_mt_drop_unused() - Inactivate slots not seen in this frame + * @dev: input device with allocated MT slots + * + * Lift all slots not seen since the last call to this function. + */ +void input_mt_drop_unused(struct input_dev *dev) +{ + struct input_mt *mt = dev->mt; + + if (mt) { + guard(spinlock_irqsave)(&dev->event_lock); + + __input_mt_drop_unused(dev, mt); + mt->frame++; + } +} +EXPORT_SYMBOL(input_mt_drop_unused); + +/** + * input_mt_release_slots() - Deactivate all slots + * @dev: input device with allocated MT slots + * + * Lift all active slots. + */ +void input_mt_release_slots(struct input_dev *dev) +{ + struct input_mt *mt = dev->mt; + + lockdep_assert_held(&dev->event_lock); + + if (mt) { + /* This will effectively mark all slots unused. */ + mt->frame++; + + __input_mt_drop_unused(dev, mt); + + if (test_bit(ABS_PRESSURE, dev->absbit)) + input_handle_event(dev, EV_ABS, ABS_PRESSURE, 0); + + mt->frame++; + } +} + +/** + * input_mt_sync_frame() - synchronize mt frame + * @dev: input device with allocated MT slots + * + * Close the frame and prepare the internal state for a new one. + * Depending on the flags, marks unused slots as inactive and performs + * pointer emulation. + */ +void input_mt_sync_frame(struct input_dev *dev) +{ + struct input_mt *mt = dev->mt; + bool use_count = false; + + if (!mt) + return; + + if (mt->flags & INPUT_MT_DROP_UNUSED) { + guard(spinlock_irqsave)(&dev->event_lock); + __input_mt_drop_unused(dev, mt); + } + + if ((mt->flags & INPUT_MT_POINTER) && !(mt->flags & INPUT_MT_SEMI_MT)) + use_count = true; + + input_mt_report_pointer_emulation(dev, use_count); + + mt->frame++; +} +EXPORT_SYMBOL(input_mt_sync_frame); + +static int adjust_dual(int *begin, int step, int *end, int eq, int mu) +{ + int f, *p, s, c; + + if (begin == end) + return 0; + + f = *begin; + p = begin + step; + s = p == end ? f + 1 : *p; + + for (; p != end; p += step) { + if (*p < f) { + s = f; + f = *p; + } else if (*p < s) { + s = *p; + } + } + + c = (f + s + 1) / 2; + if (c == 0 || (c > mu && (!eq || mu > 0))) + return 0; + /* Improve convergence for positive matrices by penalizing overcovers */ + if (s < 0 && mu <= 0) + c *= 2; + + for (p = begin; p != end; p += step) + *p -= c; + + return (c < s && s <= 0) || (f >= 0 && f < c); +} + +static void find_reduced_matrix(int *w, int nr, int nc, int nrc, int mu) +{ + int i, k, sum; + + for (k = 0; k < nrc; k++) { + for (i = 0; i < nr; i++) + adjust_dual(w + i, nr, w + i + nrc, nr <= nc, mu); + sum = 0; + for (i = 0; i < nrc; i += nr) + sum += adjust_dual(w + i, 1, w + i + nr, nc <= nr, mu); + if (!sum) + break; + } +} + +static int input_mt_set_matrix(struct input_mt *mt, + const struct input_mt_pos *pos, int num_pos, + int mu) +{ + const struct input_mt_pos *p; + struct input_mt_slot *s; + int *w = mt->red; + int x, y; + + for (s = mt->slots; s != mt->slots + mt->num_slots; s++) { + if (!input_mt_is_active(s)) + continue; + x = input_mt_get_value(s, ABS_MT_POSITION_X); + y = input_mt_get_value(s, ABS_MT_POSITION_Y); + for (p = pos; p != pos + num_pos; p++) { + int dx = x - p->x, dy = y - p->y; + *w++ = dx * dx + dy * dy - mu; + } + } + + return w - mt->red; +} + +static void input_mt_set_slots(struct input_mt *mt, + int *slots, int num_pos) +{ + struct input_mt_slot *s; + int *w = mt->red, j; + + for (j = 0; j != num_pos; j++) + slots[j] = -1; + + for (s = mt->slots; s != mt->slots + mt->num_slots; s++) { + if (!input_mt_is_active(s)) + continue; + + for (j = 0; j != num_pos; j++) { + if (w[j] < 0) { + slots[j] = s - mt->slots; + break; + } + } + + w += num_pos; + } + + for (s = mt->slots; s != mt->slots + mt->num_slots; s++) { + if (input_mt_is_active(s)) + continue; + + for (j = 0; j != num_pos; j++) { + if (slots[j] < 0) { + slots[j] = s - mt->slots; + break; + } + } + } +} + +/** + * input_mt_assign_slots() - perform a best-match assignment + * @dev: input device with allocated MT slots + * @slots: the slot assignment to be filled + * @pos: the position array to match + * @num_pos: number of positions + * @dmax: maximum ABS_MT_POSITION displacement (zero for infinite) + * + * Performs a best match against the current contacts and returns + * the slot assignment list. New contacts are assigned to unused + * slots. + * + * The assignments are balanced so that all coordinate displacements are + * below the euclidian distance dmax. If no such assignment can be found, + * some contacts are assigned to unused slots. + * + * Returns zero on success, or negative error in case of failure. + */ +int input_mt_assign_slots(struct input_dev *dev, int *slots, + const struct input_mt_pos *pos, int num_pos, + int dmax) +{ + struct input_mt *mt = dev->mt; + int mu = 2 * dmax * dmax; + int nrc; + + if (!mt || !mt->red) + return -ENXIO; + if (num_pos > mt->num_slots) + return -EINVAL; + if (num_pos < 1) + return 0; + + nrc = input_mt_set_matrix(mt, pos, num_pos, mu); + find_reduced_matrix(mt->red, num_pos, nrc / num_pos, nrc, mu); + input_mt_set_slots(mt, slots, num_pos); + + return 0; +} +EXPORT_SYMBOL(input_mt_assign_slots); + +/** + * input_mt_get_slot_by_key() - return slot matching key + * @dev: input device with allocated MT slots + * @key: the key of the sought slot + * + * Returns the slot of the given key, if it exists, otherwise + * set the key on the first unused slot and return. + * + * If no available slot can be found, -1 is returned. + * Note that for this function to work properly, input_mt_sync_frame() has + * to be called at each frame. + */ +int input_mt_get_slot_by_key(struct input_dev *dev, int key) +{ + struct input_mt *mt = dev->mt; + struct input_mt_slot *s; + + if (!mt) + return -1; + + for (s = mt->slots; s != mt->slots + mt->num_slots; s++) + if (input_mt_is_active(s) && s->key == key) + return s - mt->slots; + + for (s = mt->slots; s != mt->slots + mt->num_slots; s++) + if (!input_mt_is_active(s) && !input_mt_is_used(mt, s)) { + s->key = key; + return s - mt->slots; + } + + return -1; +} +EXPORT_SYMBOL(input_mt_get_slot_by_key); -- cgit v1.3.1