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 --- sound/usb/proc.c | 236 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 236 insertions(+) create mode 100644 sound/usb/proc.c (limited to 'sound/usb/proc.c') diff --git a/sound/usb/proc.c b/sound/usb/proc.c new file mode 100644 index 000000000..f4b7a7ff3 --- /dev/null +++ b/sound/usb/proc.c @@ -0,0 +1,236 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + */ + +#include +#include + +#include +#include +#include + +#include "usbaudio.h" +#include "helper.h" +#include "card.h" +#include "endpoint.h" +#include "proc.h" + +/* convert our full speed USB rate into sampling rate in Hz */ +static inline unsigned get_full_speed_hz(unsigned int usb_rate) +{ + return (usb_rate * 125 + (1 << 12)) >> 13; +} + +/* convert our high speed USB rate into sampling rate in Hz */ +static inline unsigned get_high_speed_hz(unsigned int usb_rate) +{ + return (usb_rate * 125 + (1 << 9)) >> 10; +} + +/* + * common proc files to show the usb device info + */ +static void proc_audio_usbbus_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer) +{ + struct snd_usb_audio *chip = entry->private_data; + if (!atomic_read(&chip->shutdown)) + snd_iprintf(buffer, "%03d/%03d\n", chip->dev->bus->busnum, chip->dev->devnum); +} + +static void proc_audio_usbid_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer) +{ + struct snd_usb_audio *chip = entry->private_data; + if (!atomic_read(&chip->shutdown)) + snd_iprintf(buffer, "%04x:%04x\n", + USB_ID_VENDOR(chip->usb_id), + USB_ID_PRODUCT(chip->usb_id)); +} + +void snd_usb_audio_create_proc(struct snd_usb_audio *chip) +{ + snd_card_ro_proc_new(chip->card, "usbbus", chip, + proc_audio_usbbus_read); + snd_card_ro_proc_new(chip->card, "usbid", chip, + proc_audio_usbid_read); +} + +static const char * const channel_labels[] = { + [SNDRV_CHMAP_NA] = "N/A", + [SNDRV_CHMAP_MONO] = "MONO", + [SNDRV_CHMAP_FL] = "FL", + [SNDRV_CHMAP_FR] = "FR", + [SNDRV_CHMAP_FC] = "FC", + [SNDRV_CHMAP_LFE] = "LFE", + [SNDRV_CHMAP_RL] = "RL", + [SNDRV_CHMAP_RR] = "RR", + [SNDRV_CHMAP_FLC] = "FLC", + [SNDRV_CHMAP_FRC] = "FRC", + [SNDRV_CHMAP_RC] = "RC", + [SNDRV_CHMAP_SL] = "SL", + [SNDRV_CHMAP_SR] = "SR", + [SNDRV_CHMAP_TC] = "TC", + [SNDRV_CHMAP_TFL] = "TFL", + [SNDRV_CHMAP_TFC] = "TFC", + [SNDRV_CHMAP_TFR] = "TFR", + [SNDRV_CHMAP_TRL] = "TRL", + [SNDRV_CHMAP_TRC] = "TRC", + [SNDRV_CHMAP_TRR] = "TRR", + [SNDRV_CHMAP_TFLC] = "TFLC", + [SNDRV_CHMAP_TFRC] = "TFRC", + [SNDRV_CHMAP_LLFE] = "LLFE", + [SNDRV_CHMAP_RLFE] = "RLFE", + [SNDRV_CHMAP_TSL] = "TSL", + [SNDRV_CHMAP_TSR] = "TSR", + [SNDRV_CHMAP_BC] = "BC", + [SNDRV_CHMAP_RLC] = "RLC", + [SNDRV_CHMAP_RRC] = "RRC", +}; + +/* + * proc interface for list the supported pcm formats + */ +static void proc_dump_substream_formats(struct snd_usb_substream *subs, struct snd_info_buffer *buffer) +{ + struct audioformat *fp; + static const char * const sync_types[4] = { + "NONE", "ASYNC", "ADAPTIVE", "SYNC" + }; + + list_for_each_entry(fp, &subs->fmt_list, list) { + snd_pcm_format_t fmt; + + snd_iprintf(buffer, " Interface %d\n", fp->iface); + snd_iprintf(buffer, " Altset %d\n", fp->altsetting); + snd_iprintf(buffer, " Format:"); + pcm_for_each_format(fmt) + if (fp->formats & pcm_format_to_bits(fmt)) + snd_iprintf(buffer, " %s", + snd_pcm_format_name(fmt)); + snd_iprintf(buffer, "\n"); + snd_iprintf(buffer, " Channels: %d\n", fp->channels); + snd_iprintf(buffer, " Endpoint: 0x%02x (%d %s) (%s)\n", + fp->endpoint, + fp->endpoint & USB_ENDPOINT_NUMBER_MASK, + fp->endpoint & USB_DIR_IN ? "IN" : "OUT", + sync_types[(fp->ep_attr & USB_ENDPOINT_SYNCTYPE) >> 2]); + if (fp->rates & SNDRV_PCM_RATE_CONTINUOUS) { + snd_iprintf(buffer, " Rates: %d - %d (continuous)\n", + fp->rate_min, fp->rate_max); + } else { + unsigned int i; + snd_iprintf(buffer, " Rates: "); + for (i = 0; i < fp->nr_rates; i++) { + if (i > 0) + snd_iprintf(buffer, ", "); + snd_iprintf(buffer, "%d", fp->rate_table[i]); + } + snd_iprintf(buffer, "\n"); + } + if (subs->speed != USB_SPEED_FULL) + snd_iprintf(buffer, " Data packet interval: %d us\n", + 125 * (1 << fp->datainterval)); + snd_iprintf(buffer, " Bits: %d\n", fp->fmt_bits); + + if (fp->dsd_raw) + snd_iprintf(buffer, " DSD raw: DOP=%d, bitrev=%d\n", + fp->dsd_dop, fp->dsd_bitrev); + + if (fp->chmap) { + const struct snd_pcm_chmap_elem *map = fp->chmap; + int c; + + snd_iprintf(buffer, " Channel map:"); + for (c = 0; c < map->channels; c++) { + if (map->map[c] >= ARRAY_SIZE(channel_labels) || + !channel_labels[map->map[c]]) + snd_iprintf(buffer, " --"); + else + snd_iprintf(buffer, " %s", + channel_labels[map->map[c]]); + } + snd_iprintf(buffer, "\n"); + } + + if (fp->sync_ep) { + snd_iprintf(buffer, " Sync Endpoint: 0x%02x (%d %s)\n", + fp->sync_ep, + fp->sync_ep & USB_ENDPOINT_NUMBER_MASK, + fp->sync_ep & USB_DIR_IN ? "IN" : "OUT"); + snd_iprintf(buffer, " Sync EP Interface: %d\n", + fp->sync_iface); + snd_iprintf(buffer, " Sync EP Altset: %d\n", + fp->sync_altsetting); + snd_iprintf(buffer, " Implicit Feedback Mode: %s\n", + fp->implicit_fb ? "Yes" : "No"); + } + + // snd_iprintf(buffer, " Max Packet Size = %d\n", fp->maxpacksize); + // snd_iprintf(buffer, " EP Attribute = %#x\n", fp->attributes); + } +} + +static void proc_dump_ep_status(struct snd_usb_substream *subs, + struct snd_usb_endpoint *data_ep, + struct snd_usb_endpoint *sync_ep, + struct snd_info_buffer *buffer) +{ + if (!data_ep) + return; + snd_iprintf(buffer, " Packet Size = %d\n", data_ep->curpacksize); + snd_iprintf(buffer, " Momentary freq = %u Hz (%#x.%04x)\n", + subs->speed == USB_SPEED_FULL + ? get_full_speed_hz(data_ep->freqm) + : get_high_speed_hz(data_ep->freqm), + data_ep->freqm >> 16, data_ep->freqm & 0xffff); + if (sync_ep && data_ep->freqshift != INT_MIN) { + int res = 16 - data_ep->freqshift; + snd_iprintf(buffer, " Feedback Format = %d.%d\n", + (sync_ep->syncmaxsize > 3 ? 32 : 24) - res, res); + } +} + +static void proc_dump_substream_status(struct snd_usb_audio *chip, + struct snd_usb_substream *subs, + struct snd_info_buffer *buffer) +{ + guard(mutex)(&chip->mutex); + if (subs->running) { + snd_iprintf(buffer, " Status: Running\n"); + if (subs->cur_audiofmt) { + snd_iprintf(buffer, " Interface = %d\n", subs->cur_audiofmt->iface); + snd_iprintf(buffer, " Altset = %d\n", subs->cur_audiofmt->altsetting); + } + proc_dump_ep_status(subs, subs->data_endpoint, subs->sync_endpoint, buffer); + } else { + snd_iprintf(buffer, " Status: Stop\n"); + } +} + +static void proc_pcm_format_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer) +{ + struct snd_usb_stream *stream = entry->private_data; + struct snd_usb_audio *chip = stream->chip; + + snd_iprintf(buffer, "%s : %s\n", chip->card->longname, stream->pcm->name); + + if (stream->substream[SNDRV_PCM_STREAM_PLAYBACK].num_formats) { + snd_iprintf(buffer, "\nPlayback:\n"); + proc_dump_substream_status(chip, &stream->substream[SNDRV_PCM_STREAM_PLAYBACK], buffer); + proc_dump_substream_formats(&stream->substream[SNDRV_PCM_STREAM_PLAYBACK], buffer); + } + if (stream->substream[SNDRV_PCM_STREAM_CAPTURE].num_formats) { + snd_iprintf(buffer, "\nCapture:\n"); + proc_dump_substream_status(chip, &stream->substream[SNDRV_PCM_STREAM_CAPTURE], buffer); + proc_dump_substream_formats(&stream->substream[SNDRV_PCM_STREAM_CAPTURE], buffer); + } +} + +void snd_usb_proc_pcm_format_add(struct snd_usb_stream *stream) +{ + char name[32]; + struct snd_card *card = stream->chip->card; + + scnprintf(name, sizeof(name), "stream%d", stream->pcm_index); + snd_card_ro_proc_new(card, name, stream, proc_pcm_format_read); +} + -- cgit v1.3.1