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/validate.c | 366 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 366 insertions(+) create mode 100644 sound/usb/validate.c (limited to 'sound/usb/validate.c') diff --git a/sound/usb/validate.c b/sound/usb/validate.c new file mode 100644 index 000000000..f62b7cc04 --- /dev/null +++ b/sound/usb/validate.c @@ -0,0 +1,366 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +// +// Validation of USB-audio class descriptors +// + +#include +#include +#include +#include +#include +#include +#include "usbaudio.h" +#include "helper.h" + +struct usb_desc_validator { + unsigned char protocol; + unsigned char type; + bool (*func)(const void *p, const struct usb_desc_validator *v); + size_t size; +}; + +#define UAC_VERSION_ALL (unsigned char)(-1) + +/* UAC1 only */ +static bool validate_uac1_header(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac1_ac_header_descriptor *d = p; + + return d->bLength >= sizeof(*d) && + d->bLength >= sizeof(*d) + d->bInCollection; +} + +/* for mixer unit; covering all UACs */ +static bool validate_mixer_unit(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac_mixer_unit_descriptor *d = p; + size_t len; + + if (d->bLength < sizeof(*d) || !d->bNrInPins) + return false; + len = sizeof(*d) + d->bNrInPins; + /* We can't determine the bitmap size only from this unit descriptor, + * so just check with the remaining length. + * The actual bitmap is checked at mixer unit parser. + */ + switch (v->protocol) { + case UAC_VERSION_1: + default: + len += 2 + 1; /* wChannelConfig, iChannelNames */ + /* bmControls[n*m] */ + len += 1; /* iMixer */ + break; + case UAC_VERSION_2: + len += 4 + 1; /* bmChannelConfig, iChannelNames */ + /* bmMixerControls[n*m] */ + len += 1 + 1; /* bmControls, iMixer */ + break; + case UAC_VERSION_3: + len += 2; /* wClusterDescrID */ + /* bmMixerControls[n*m] */ + break; + } + return d->bLength >= len; +} + +/* both for processing and extension units; covering all UACs */ +static bool validate_processing_unit(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac_processing_unit_descriptor *d = p; + const unsigned char *hdr = p; + size_t len, m; + + if (d->bLength < sizeof(*d)) + return false; + len = sizeof(*d) + d->bNrInPins; + if (d->bLength < len) + return false; + switch (v->protocol) { + case UAC_VERSION_1: + default: + /* bNrChannels, wChannelConfig, iChannelNames */ + len += 1 + 2 + 1; + if (d->bLength < len + 1) /* bControlSize */ + return false; + m = hdr[len]; + len += 1 + m + 1; /* bControlSize, bmControls, iProcessing */ + break; + case UAC_VERSION_2: + /* bNrChannels, bmChannelConfig, iChannelNames */ + len += 1 + 4 + 1; + if (v->type == UAC2_PROCESSING_UNIT_V2) + len += 2; /* bmControls -- 2 bytes for PU */ + else + len += 1; /* bmControls -- 1 byte for EU */ + len += 1; /* iProcessing */ + break; + case UAC_VERSION_3: + /* wProcessingDescrStr, bmControls */ + len += 2 + 4; + break; + } + if (d->bLength < len) + return false; + + switch (v->protocol) { + case UAC_VERSION_1: + default: + if (v->type == UAC1_EXTENSION_UNIT) + return true; /* OK */ + switch (le16_to_cpu(d->wProcessType)) { + case UAC_PROCESS_UP_DOWNMIX: + case UAC_PROCESS_DOLBY_PROLOGIC: + if (d->bLength < len + 1) /* bNrModes */ + return false; + m = hdr[len]; + len += 1 + m * 2; /* bNrModes, waModes(n) */ + break; + default: + break; + } + break; + case UAC_VERSION_2: + if (v->type == UAC2_EXTENSION_UNIT_V2) + return true; /* OK */ + switch (le16_to_cpu(d->wProcessType)) { + case UAC2_PROCESS_UP_DOWNMIX: + case UAC2_PROCESS_DOLBY_PROLOCIC: /* SiC! */ + if (d->bLength < len + 1) /* bNrModes */ + return false; + m = hdr[len]; + len += 1 + m * 4; /* bNrModes, daModes(n) */ + break; + default: + break; + } + break; + case UAC_VERSION_3: + if (v->type == UAC3_EXTENSION_UNIT) { + len += 2; /* wClusterDescrID */ + break; + } + switch (le16_to_cpu(d->wProcessType)) { + case UAC3_PROCESS_UP_DOWNMIX: + if (d->bLength < len + 1) /* bNrModes */ + return false; + m = hdr[len]; + len += 1 + m * 2; /* bNrModes, waClusterDescrID(n) */ + break; + case UAC3_PROCESS_MULTI_FUNCTION: + len += 2 + 4; /* wClusterDescrID, bmAlgorighms */ + break; + default: + break; + } + break; + } + if (d->bLength < len) + return false; + + return true; +} + +/* both for selector and clock selector units; covering all UACs */ +static bool validate_selector_unit(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac_selector_unit_descriptor *d = p; + size_t len; + + if (d->bLength < sizeof(*d)) + return false; + len = sizeof(*d) + d->bNrInPins; + switch (v->protocol) { + case UAC_VERSION_1: + default: + len += 1; /* iSelector */ + break; + case UAC_VERSION_2: + len += 1 + 1; /* bmControls, iSelector */ + break; + case UAC_VERSION_3: + len += 4 + 2; /* bmControls, wSelectorDescrStr */ + break; + } + return d->bLength >= len; +} + +static bool validate_uac1_feature_unit(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac_feature_unit_descriptor *d = p; + + if (d->bLength < sizeof(*d) || !d->bControlSize) + return false; + /* at least bmaControls(0) for master channel + iFeature */ + return d->bLength >= sizeof(*d) + d->bControlSize + 1; +} + +static bool validate_uac2_feature_unit(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac2_feature_unit_descriptor *d = p; + + if (d->bLength < sizeof(*d)) + return false; + /* at least bmaControls(0) for master channel + iFeature */ + return d->bLength >= sizeof(*d) + 4 + 1; +} + +static bool validate_uac3_feature_unit(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac3_feature_unit_descriptor *d = p; + + if (d->bLength < sizeof(*d)) + return false; + /* at least bmaControls(0) for master channel + wFeatureDescrStr */ + return d->bLength >= sizeof(*d) + 4 + 2; +} + +static bool validate_uac3_power_domain_unit(const void *p, + const struct usb_desc_validator *v) +{ + const struct uac3_power_domain_descriptor *d = p; + + if (d->bLength < sizeof(*d)) + return false; + /* baEntities[] + wPDomainDescrStr */ + return d->bLength >= sizeof(*d) + d->bNrEntities + 2; +} + +static bool validate_midi_out_jack(const void *p, + const struct usb_desc_validator *v) +{ + const struct usb_midi_out_jack_descriptor *d = p; + + return d->bLength >= sizeof(*d) && + d->bLength >= sizeof(*d) + d->bNrInputPins * 2; +} + +#define FIXED(p, t, s) { .protocol = (p), .type = (t), .size = sizeof(s) } +#define FUNC(p, t, f) { .protocol = (p), .type = (t), .func = (f) } + +static const struct usb_desc_validator audio_validators[] = { + /* UAC1 */ + FUNC(UAC_VERSION_1, UAC_HEADER, validate_uac1_header), + FIXED(UAC_VERSION_1, UAC_INPUT_TERMINAL, + struct uac_input_terminal_descriptor), + FIXED(UAC_VERSION_1, UAC_OUTPUT_TERMINAL, + struct uac1_output_terminal_descriptor), + FUNC(UAC_VERSION_1, UAC_MIXER_UNIT, validate_mixer_unit), + FUNC(UAC_VERSION_1, UAC_SELECTOR_UNIT, validate_selector_unit), + FUNC(UAC_VERSION_1, UAC_FEATURE_UNIT, validate_uac1_feature_unit), + FUNC(UAC_VERSION_1, UAC1_PROCESSING_UNIT, validate_processing_unit), + FUNC(UAC_VERSION_1, UAC1_EXTENSION_UNIT, validate_processing_unit), + + /* UAC2 */ + FIXED(UAC_VERSION_2, UAC_HEADER, struct uac2_ac_header_descriptor), + FIXED(UAC_VERSION_2, UAC_INPUT_TERMINAL, + struct uac2_input_terminal_descriptor), + FIXED(UAC_VERSION_2, UAC_OUTPUT_TERMINAL, + struct uac2_output_terminal_descriptor), + FUNC(UAC_VERSION_2, UAC_MIXER_UNIT, validate_mixer_unit), + FUNC(UAC_VERSION_2, UAC_SELECTOR_UNIT, validate_selector_unit), + FUNC(UAC_VERSION_2, UAC_FEATURE_UNIT, validate_uac2_feature_unit), + /* just a stop-gap, it should be a proper function for the array + * once if the unit is really parsed/used + */ + FIXED(UAC_VERSION_2, UAC2_EFFECT_UNIT, + struct uac2_effect_unit_descriptor), + FUNC(UAC_VERSION_2, UAC2_PROCESSING_UNIT_V2, validate_processing_unit), + FUNC(UAC_VERSION_2, UAC2_EXTENSION_UNIT_V2, validate_processing_unit), + FIXED(UAC_VERSION_2, UAC2_CLOCK_SOURCE, + struct uac_clock_source_descriptor), + FUNC(UAC_VERSION_2, UAC2_CLOCK_SELECTOR, validate_selector_unit), + FIXED(UAC_VERSION_2, UAC2_CLOCK_MULTIPLIER, + struct uac_clock_multiplier_descriptor), + /* UAC_VERSION_2, UAC2_SAMPLE_RATE_CONVERTER: not implemented yet */ + + /* UAC3 */ + FIXED(UAC_VERSION_3, UAC_HEADER, struct uac3_ac_header_descriptor), + FIXED(UAC_VERSION_3, UAC_INPUT_TERMINAL, + struct uac3_input_terminal_descriptor), + FIXED(UAC_VERSION_3, UAC_OUTPUT_TERMINAL, + struct uac3_output_terminal_descriptor), + /* UAC_VERSION_3, UAC3_EXTENDED_TERMINAL: not implemented yet */ + FUNC(UAC_VERSION_3, UAC3_MIXER_UNIT, validate_mixer_unit), + FUNC(UAC_VERSION_3, UAC3_SELECTOR_UNIT, validate_selector_unit), + FUNC(UAC_VERSION_3, UAC3_FEATURE_UNIT, validate_uac3_feature_unit), + FIXED(UAC_VERSION_3, UAC3_EFFECT_UNIT, + struct uac2_effect_unit_descriptor), /* sharing the same struct */ + FUNC(UAC_VERSION_3, UAC3_PROCESSING_UNIT, validate_processing_unit), + FUNC(UAC_VERSION_3, UAC3_EXTENSION_UNIT, validate_processing_unit), + FIXED(UAC_VERSION_3, UAC3_CLOCK_SOURCE, + struct uac3_clock_source_descriptor), + FUNC(UAC_VERSION_3, UAC3_CLOCK_SELECTOR, validate_selector_unit), + FIXED(UAC_VERSION_3, UAC3_CLOCK_MULTIPLIER, + struct uac3_clock_multiplier_descriptor), + /* UAC_VERSION_3, UAC3_SAMPLE_RATE_CONVERTER: not implemented yet */ + /* UAC_VERSION_3, UAC3_CONNECTORS: not implemented yet */ + FUNC(UAC_VERSION_3, UAC3_POWER_DOMAIN, validate_uac3_power_domain_unit), + { } /* terminator */ +}; + +static const struct usb_desc_validator midi_validators[] = { + FIXED(UAC_VERSION_ALL, USB_MS_HEADER, + struct usb_ms_header_descriptor), + FIXED(UAC_VERSION_ALL, USB_MS_MIDI_IN_JACK, + struct usb_midi_in_jack_descriptor), + FUNC(UAC_VERSION_ALL, USB_MS_MIDI_OUT_JACK, + validate_midi_out_jack), + { } /* terminator */ +}; + + +/* Validate the given unit descriptor, return true if it's OK */ +static bool validate_desc(unsigned char *hdr, int protocol, + const struct usb_desc_validator *v) +{ + if (hdr[1] != USB_DT_CS_INTERFACE) + return true; /* don't care */ + + for (; v->type; v++) { + if (v->type == hdr[2] && + (v->protocol == UAC_VERSION_ALL || + v->protocol == protocol)) { + if (v->func) + return v->func(hdr, v); + /* check for the fixed size */ + return hdr[0] >= v->size; + } + } + + return true; /* not matching, skip validation */ +} + +bool snd_usb_validate_audio_desc(void *p, int protocol) +{ + unsigned char *c = p; + bool valid; + + valid = validate_desc(p, protocol, audio_validators); + if (!valid && snd_usb_skip_validation) { + print_hex_dump(KERN_ERR, "USB-audio: buggy audio desc: ", + DUMP_PREFIX_NONE, 16, 1, c, c[0], true); + valid = true; + } + return valid; +} + +bool snd_usb_validate_midi_desc(void *p) +{ + unsigned char *c = p; + bool valid; + + valid = validate_desc(p, UAC_VERSION_1, midi_validators); + if (!valid && snd_usb_skip_validation) { + print_hex_dump(KERN_ERR, "USB-audio: buggy midi desc: ", + DUMP_PREFIX_NONE, 16, 1, c, c[0], true); + valid = true; + } + return valid; +} -- cgit v1.3.1