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/media/rc/ir-xmp-decoder.c | 217 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 217 insertions(+) create mode 100644 drivers/media/rc/ir-xmp-decoder.c (limited to 'drivers/media/rc/ir-xmp-decoder.c') diff --git a/drivers/media/rc/ir-xmp-decoder.c b/drivers/media/rc/ir-xmp-decoder.c new file mode 100644 index 000000000..dc36b6873 --- /dev/null +++ b/drivers/media/rc/ir-xmp-decoder.c @@ -0,0 +1,217 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* ir-xmp-decoder.c - handle XMP IR Pulse/Space protocol + * + * Copyright (C) 2014 by Marcel Mol + * + * - Based on info from http://www.hifi-remote.com + * - Ignore Toggle=9 frames + * - Ignore XMP-1 XMP-2 difference, always store 16 bit OBC + */ + +#include +#include +#include "rc-core-priv.h" + +#define XMP_UNIT 136 /* us */ +#define XMP_LEADER 210 /* us */ +#define XMP_NIBBLE_PREFIX 760 /* us */ +#define XMP_HALFFRAME_SPACE 13800 /* us */ +/* should be 80ms but not all duration supliers can go that high */ +#define XMP_TRAILER_SPACE 20000 + +enum xmp_state { + STATE_INACTIVE, + STATE_LEADER_PULSE, + STATE_NIBBLE_SPACE, +}; + +/** + * ir_xmp_decode() - Decode one XMP pulse or space + * @dev: the struct rc_dev descriptor of the device + * @ev: the struct ir_raw_event descriptor of the pulse/space + * + * This function returns -EINVAL if the pulse violates the state machine + */ +static int ir_xmp_decode(struct rc_dev *dev, struct ir_raw_event ev) +{ + struct xmp_dec *data = &dev->raw->xmp; + + if (!is_timing_event(ev)) { + if (ev.overflow) + data->state = STATE_INACTIVE; + return 0; + } + + dev_dbg(&dev->dev, "XMP decode started at state %d %d (%uus %s)\n", + data->state, data->count, ev.duration, TO_STR(ev.pulse)); + + switch (data->state) { + + case STATE_INACTIVE: + if (!ev.pulse) + break; + + if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2)) { + data->count = 0; + data->state = STATE_NIBBLE_SPACE; + } + + return 0; + + case STATE_LEADER_PULSE: + if (!ev.pulse) + break; + + if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2)) + data->state = STATE_NIBBLE_SPACE; + + return 0; + + case STATE_NIBBLE_SPACE: + if (ev.pulse) + break; + + if (geq_margin(ev.duration, XMP_TRAILER_SPACE, XMP_NIBBLE_PREFIX)) { + int divider, i; + u8 addr, subaddr, subaddr2, toggle, oem, obc1, obc2, sum1, sum2; + u32 *n; + u32 scancode; + + if (data->count != 16) { + dev_dbg(&dev->dev, "received TRAILER period at index %d: %u\n", + data->count, ev.duration); + data->state = STATE_INACTIVE; + return -EINVAL; + } + + n = data->durations; + /* + * the 4th nibble should be 15 so base the divider on this + * to transform durations into nibbles. Subtract 2000 from + * the divider to compensate for fluctuations in the signal + */ + divider = (n[3] - XMP_NIBBLE_PREFIX) / 15 - 2000; + if (divider < 50) { + dev_dbg(&dev->dev, "divider to small %d.\n", + divider); + data->state = STATE_INACTIVE; + return -EINVAL; + } + + /* convert to nibbles and do some sanity checks */ + for (i = 0; i < 16; i++) + n[i] = (n[i] - XMP_NIBBLE_PREFIX) / divider; + sum1 = (15 + n[0] + n[1] + n[2] + n[3] + + n[4] + n[5] + n[6] + n[7]) % 16; + sum2 = (15 + n[8] + n[9] + n[10] + n[11] + + n[12] + n[13] + n[14] + n[15]) % 16; + + if (sum1 != 15 || sum2 != 15) { + dev_dbg(&dev->dev, "checksum errors sum1=0x%X sum2=0x%X\n", + sum1, sum2); + data->state = STATE_INACTIVE; + return -EINVAL; + } + + subaddr = n[0] << 4 | n[2]; + subaddr2 = n[8] << 4 | n[11]; + oem = n[4] << 4 | n[5]; + addr = n[6] << 4 | n[7]; + toggle = n[10]; + obc1 = n[12] << 4 | n[13]; + obc2 = n[14] << 4 | n[15]; + if (subaddr != subaddr2) { + dev_dbg(&dev->dev, "subaddress nibbles mismatch 0x%02X != 0x%02X\n", + subaddr, subaddr2); + data->state = STATE_INACTIVE; + return -EINVAL; + } + if (oem != 0x44) + dev_dbg(&dev->dev, "Warning: OEM nibbles 0x%02X. Expected 0x44\n", + oem); + + scancode = addr << 24 | subaddr << 16 | + obc1 << 8 | obc2; + dev_dbg(&dev->dev, "XMP scancode 0x%06x\n", scancode); + + if (toggle == 0) { + rc_keydown(dev, RC_PROTO_XMP, scancode, 0); + } else { + rc_repeat(dev); + dev_dbg(&dev->dev, "Repeat last key\n"); + } + data->state = STATE_INACTIVE; + + return 0; + + } else if (geq_margin(ev.duration, XMP_HALFFRAME_SPACE, XMP_NIBBLE_PREFIX)) { + /* Expect 8 or 16 nibble pulses. 16 in case of 'final' frame */ + if (data->count == 16) { + dev_dbg(&dev->dev, "received half frame pulse at index %d. Probably a final frame key-up event: %u\n", + data->count, ev.duration); + /* + * TODO: for now go back to half frame position + * so trailer can be found and key press + * can be handled. + */ + data->count = 8; + } + + else if (data->count != 8) + dev_dbg(&dev->dev, "received half frame pulse at index %d: %u\n", + data->count, ev.duration); + data->state = STATE_LEADER_PULSE; + + return 0; + + } else if (geq_margin(ev.duration, XMP_NIBBLE_PREFIX, XMP_UNIT)) { + /* store nibble raw data, decode after trailer */ + if (data->count == 16) { + dev_dbg(&dev->dev, "too many pulses (%d) ignoring: %u\n", + data->count, ev.duration); + data->state = STATE_INACTIVE; + return -EINVAL; + } + data->durations[data->count] = ev.duration; + data->count++; + data->state = STATE_LEADER_PULSE; + + return 0; + + } + + break; + } + + dev_dbg(&dev->dev, "XMP decode failed at count %d state %d (%uus %s)\n", + data->count, data->state, ev.duration, TO_STR(ev.pulse)); + data->state = STATE_INACTIVE; + return -EINVAL; +} + +static struct ir_raw_handler xmp_handler = { + .protocols = RC_PROTO_BIT_XMP, + .decode = ir_xmp_decode, + .min_timeout = XMP_TRAILER_SPACE, +}; + +static int __init ir_xmp_decode_init(void) +{ + ir_raw_handler_register(&xmp_handler); + + printk(KERN_INFO "IR XMP protocol handler initialized\n"); + return 0; +} + +static void __exit ir_xmp_decode_exit(void) +{ + ir_raw_handler_unregister(&xmp_handler); +} + +module_init(ir_xmp_decode_init); +module_exit(ir_xmp_decode_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Marcel Mol "); +MODULE_AUTHOR("MESA Consulting (http://www.mesa.nl)"); +MODULE_DESCRIPTION("XMP IR protocol decoder"); -- cgit v1.3.1