x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

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) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 494 insertions, 0 deletions

diff --git a/sound/usb/implicit.c b/sound/usb/implicit.c
new file mode 100644
index 000000000..77f06da93
--- /dev/null
+++ b/sound/usb/implicit.c
@@ -0,0 +1,494 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+//
+// Special handling for implicit feedback mode
+//
+
+#include <linux/init.h>
+#include <linux/usb.h>
+#include <linux/usb/audio.h>
+#include <linux/usb/audio-v2.h>
+
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+
+#include "usbaudio.h"
+#include "card.h"
+#include "helper.h"
+#include "pcm.h"
+#include "implicit.h"
+
+enum {
+	IMPLICIT_FB_NONE,
+	IMPLICIT_FB_GENERIC,
+	IMPLICIT_FB_FIXED,
+	IMPLICIT_FB_BOTH,	/* generic playback + capture (for BOSS) */
+};
+
+struct snd_usb_implicit_fb_match {
+	unsigned int id;
+	unsigned int iface_class;
+	unsigned int ep_num;
+	unsigned int iface;
+	int type;
+};
+
+#define IMPLICIT_FB_GENERIC_DEV(vend, prod) \
+	{ .id = USB_ID(vend, prod), .type = IMPLICIT_FB_GENERIC }
+#define IMPLICIT_FB_FIXED_DEV(vend, prod, ep, ifnum) \
+	{ .id = USB_ID(vend, prod), .type = IMPLICIT_FB_FIXED, .ep_num = (ep),\
+	    .iface = (ifnum) }
+#define IMPLICIT_FB_BOTH_DEV(vend, prod, ep, ifnum) \
+	{ .id = USB_ID(vend, prod), .type = IMPLICIT_FB_BOTH, .ep_num = (ep),\
+	    .iface = (ifnum) }
+#define IMPLICIT_FB_SKIP_DEV(vend, prod) \
+	{ .id = USB_ID(vend, prod), .type = IMPLICIT_FB_NONE }
+
+/* Implicit feedback quirk table for playback */
+static const struct snd_usb_implicit_fb_match playback_implicit_fb_quirks[] = {
+	/* Fixed EP */
+	/* FIXME: check the availability of generic matching */
+	IMPLICIT_FB_FIXED_DEV(0x0763, 0x2030, 0x81, 3), /* M-Audio Fast Track C400 */
+	IMPLICIT_FB_FIXED_DEV(0x0763, 0x2031, 0x81, 3), /* M-Audio Fast Track C600 */
+	IMPLICIT_FB_FIXED_DEV(0x0763, 0x2080, 0x81, 2), /* M-Audio FastTrack Ultra */
+	IMPLICIT_FB_FIXED_DEV(0x0763, 0x2081, 0x81, 2), /* M-Audio FastTrack Ultra */
+	IMPLICIT_FB_FIXED_DEV(0x2466, 0x8010, 0x81, 2), /* Fractal Audio Axe-Fx III */
+	IMPLICIT_FB_FIXED_DEV(0x31e9, 0x0001, 0x81, 2), /* Solid State Logic SSL2 */
+	IMPLICIT_FB_FIXED_DEV(0x31e9, 0x0002, 0x81, 2), /* Solid State Logic SSL2+ */
+	IMPLICIT_FB_FIXED_DEV(0x0499, 0x172f, 0x81, 2), /* Steinberg UR22C */
+	IMPLICIT_FB_FIXED_DEV(0x0d9a, 0x00df, 0x81, 2), /* RTX6001 */
+	IMPLICIT_FB_FIXED_DEV(0x19f7, 0x000a, 0x84, 3), /* RODE AI-1 */
+	IMPLICIT_FB_FIXED_DEV(0x22f0, 0x0006, 0x81, 3), /* Allen&Heath Qu-16 */
+	IMPLICIT_FB_FIXED_DEV(0x1686, 0xf029, 0x82, 2), /* Zoom UAC-2 */
+	IMPLICIT_FB_FIXED_DEV(0x2466, 0x8003, 0x86, 2), /* Fractal Audio Axe-Fx II */
+	IMPLICIT_FB_FIXED_DEV(0x0499, 0x172a, 0x86, 2), /* Yamaha MODX */
+
+	/* Special matching */
+	{ .id = USB_ID(0x07fd, 0x0004), .iface_class = USB_CLASS_AUDIO,
+	  .type = IMPLICIT_FB_NONE },		/* MicroBook IIc */
+	/* ep = 0x84, ifnum = 0 */
+	{ .id = USB_ID(0x07fd, 0x0004), .iface_class = USB_CLASS_VENDOR_SPEC,
+	  .type = IMPLICIT_FB_FIXED,
+	  .ep_num = 0x84, .iface = 0 },		/* MOTU MicroBook II */
+
+	{} /* terminator */
+};
+
+/* Implicit feedback quirk table for capture: only FIXED type */
+static const struct snd_usb_implicit_fb_match capture_implicit_fb_quirks[] = {
+	{} /* terminator */
+};
+
+/* set up sync EP information on the audioformat */
+static int add_implicit_fb_sync_ep(struct snd_usb_audio *chip,
+				   struct audioformat *fmt,
+				   int ep, int ep_idx, int ifnum,
+				   const struct usb_host_interface *alts)
+{
+	struct usb_interface *iface;
+
+	if (!alts) {
+		iface = usb_ifnum_to_if(chip->dev, ifnum);
+		if (!iface || iface->num_altsetting < 2)
+			return 0;
+		alts = &iface->altsetting[1];
+	}
+
+	fmt->sync_ep = ep;
+	fmt->sync_iface = ifnum;
+	fmt->sync_altsetting = alts->desc.bAlternateSetting;
+	fmt->sync_ep_idx = ep_idx;
+	fmt->implicit_fb = 1;
+	usb_audio_dbg(chip,
+		      "%d:%d: added %s implicit_fb sync_ep %x, iface %d:%d\n",
+		      fmt->iface, fmt->altsetting,
+		      (ep & USB_DIR_IN) ? "playback" : "capture",
+		      fmt->sync_ep, fmt->sync_iface, fmt->sync_altsetting);
+	return 1;
+}
+
+/* Check whether the given UAC2 iface:altset points to an implicit fb source */
+static int add_generic_uac2_implicit_fb(struct snd_usb_audio *chip,
+					struct audioformat *fmt,
+					unsigned int ifnum,
+					unsigned int altsetting)
+{
+	struct usb_host_interface *alts;
+	struct usb_endpoint_descriptor *epd;
+
+	alts = snd_usb_get_host_interface(chip, ifnum, altsetting);
+	if (!alts)
+		return 0;
+	if (alts->desc.bInterfaceClass != USB_CLASS_AUDIO ||
+	    alts->desc.bInterfaceSubClass != USB_SUBCLASS_AUDIOSTREAMING ||
+	    alts->desc.bInterfaceProtocol != UAC_VERSION_2 ||
+	    alts->desc.bNumEndpoints < 1)
+		return 0;
+	epd = get_endpoint(alts, 0);
+	if (!usb_endpoint_is_isoc_in(epd) ||
+	    (epd->bmAttributes & USB_ENDPOINT_USAGE_MASK) !=
+					USB_ENDPOINT_USAGE_IMPLICIT_FB)
+		return 0;
+	return add_implicit_fb_sync_ep(chip, fmt, epd->bEndpointAddress, 0,
+				       ifnum, alts);
+}
+
+static bool roland_sanity_check_iface(struct usb_host_interface *alts)
+{
+	if (alts->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC ||
+	    (alts->desc.bInterfaceSubClass != 2 &&
+	     alts->desc.bInterfaceProtocol != 2) ||
+	    alts->desc.bNumEndpoints < 1)
+		return false;
+	return true;
+}
+
+/* Like the UAC2 case above, but specific to Roland with vendor class and hack */
+static int add_roland_implicit_fb(struct snd_usb_audio *chip,
+				  struct audioformat *fmt,
+				  struct usb_host_interface *alts)
+{
+	struct usb_endpoint_descriptor *epd;
+
+	if (!roland_sanity_check_iface(alts))
+		return 0;
+	/* only when both streams are with ASYNC type */
+	epd = get_endpoint(alts, 0);
+	if (!usb_endpoint_is_isoc_out(epd) ||
+	    (epd->bmAttributes & USB_ENDPOINT_SYNCTYPE) != USB_ENDPOINT_SYNC_ASYNC)
+		return 0;
+
+	/* check capture EP */
+	alts = snd_usb_get_host_interface(chip,
+					  alts->desc.bInterfaceNumber + 1,
+					  alts->desc.bAlternateSetting);
+	if (!alts || !roland_sanity_check_iface(alts))
+		return 0;
+	epd = get_endpoint(alts, 0);
+	if (!usb_endpoint_is_isoc_in(epd) ||
+	    (epd->bmAttributes & USB_ENDPOINT_SYNCTYPE) != USB_ENDPOINT_SYNC_ASYNC)
+		return 0;
+	chip->quirk_flags |= QUIRK_FLAG_PLAYBACK_FIRST;
+	return add_implicit_fb_sync_ep(chip, fmt, epd->bEndpointAddress, 0,
+				       alts->desc.bInterfaceNumber, alts);
+}
+
+/* capture quirk for Roland device; always full-duplex */
+static int add_roland_capture_quirk(struct snd_usb_audio *chip,
+				    struct audioformat *fmt,
+				    struct usb_host_interface *alts)
+{
+	struct usb_endpoint_descriptor *epd;
+
+	if (!roland_sanity_check_iface(alts))
+		return 0;
+	epd = get_endpoint(alts, 0);
+	if (!usb_endpoint_is_isoc_in(epd) ||
+	    (epd->bmAttributes & USB_ENDPOINT_SYNCTYPE) != USB_ENDPOINT_SYNC_ASYNC)
+		return 0;
+
+	alts = snd_usb_get_host_interface(chip,
+					  alts->desc.bInterfaceNumber - 1,
+					  alts->desc.bAlternateSetting);
+	if (!alts || !roland_sanity_check_iface(alts))
+		return 0;
+	epd = get_endpoint(alts, 0);
+	if (!usb_endpoint_is_isoc_out(epd))
+		return 0;
+	return add_implicit_fb_sync_ep(chip, fmt, epd->bEndpointAddress, 0,
+				       alts->desc.bInterfaceNumber, alts);
+}
+
+/* Playback and capture EPs on Pioneer devices share the same iface/altset
+ * for the implicit feedback operation
+ */
+static bool is_pioneer_implicit_fb(struct snd_usb_audio *chip,
+				   struct usb_host_interface *alts)
+
+{
+	struct usb_endpoint_descriptor *epd;
+
+	if (USB_ID_VENDOR(chip->usb_id) != 0x2b73 &&
+	    USB_ID_VENDOR(chip->usb_id) != 0x08e4)
+		return false;
+	if (alts->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC)
+		return false;
+	if (alts->desc.bNumEndpoints != 2)
+		return false;
+
+	epd = get_endpoint(alts, 0);
+	if (!usb_endpoint_is_isoc_out(epd) ||
+	    (epd->bmAttributes & USB_ENDPOINT_SYNCTYPE) != USB_ENDPOINT_SYNC_ASYNC)
+		return false;
+
+	epd = get_endpoint(alts, 1);
+	if (!usb_endpoint_is_isoc_in(epd) ||
+	    (epd->bmAttributes & USB_ENDPOINT_SYNCTYPE) != USB_ENDPOINT_SYNC_ASYNC ||
+	    ((epd->bmAttributes & USB_ENDPOINT_USAGE_MASK) !=
+	     USB_ENDPOINT_USAGE_DATA &&
+	     (epd->bmAttributes & USB_ENDPOINT_USAGE_MASK) !=
+	     USB_ENDPOINT_USAGE_IMPLICIT_FB))
+		return false;
+
+	return true;
+}
+
+static int __add_generic_implicit_fb(struct snd_usb_audio *chip,
+				     struct audioformat *fmt,
+				     int iface, int altset)
+{
+	struct usb_host_interface *alts;
+	struct usb_endpoint_descriptor *epd;
+
+	alts = snd_usb_get_host_interface(chip, iface, altset);
+	if (!alts)
+		return 0;
+
+	if ((alts->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC &&
+	     alts->desc.bInterfaceClass != USB_CLASS_AUDIO) ||
+	    alts->desc.bNumEndpoints < 1)
+		return 0;
+	epd = get_endpoint(alts, 0);
+	if (!usb_endpoint_is_isoc_in(epd) ||
+	    (epd->bmAttributes & USB_ENDPOINT_SYNCTYPE) != USB_ENDPOINT_SYNC_ASYNC)
+		return 0;
+	return add_implicit_fb_sync_ep(chip, fmt, epd->bEndpointAddress, 0,
+				       iface, alts);
+}
+
+/* More generic quirk: look for the sync EP next to the data EP */
+static int add_generic_implicit_fb(struct snd_usb_audio *chip,
+				   struct audioformat *fmt,
+				   struct usb_host_interface *alts)
+{
+	if ((fmt->ep_attr & USB_ENDPOINT_SYNCTYPE) != USB_ENDPOINT_SYNC_ASYNC)
+		return 0;
+
+	if (__add_generic_implicit_fb(chip, fmt,
+				      alts->desc.bInterfaceNumber + 1,
+				      alts->desc.bAlternateSetting))
+		return 1;
+	return __add_generic_implicit_fb(chip, fmt,
+					 alts->desc.bInterfaceNumber - 1,
+					 alts->desc.bAlternateSetting);
+}
+
+static const struct snd_usb_implicit_fb_match *
+find_implicit_fb_entry(struct snd_usb_audio *chip,
+		       const struct snd_usb_implicit_fb_match *match,
+		       const struct usb_host_interface *alts)
+{
+	for (; match->id; match++)
+		if (match->id == chip->usb_id &&
+		    (!match->iface_class ||
+		     (alts->desc.bInterfaceClass == match->iface_class)))
+			return match;
+
+	return NULL;
+}
+
+/* Setup an implicit feedback endpoint from a quirk. Returns 0 if no quirk
+ * applies. Returns 1 if a quirk was found.
+ */
+static int audioformat_implicit_fb_quirk(struct snd_usb_audio *chip,
+					 struct audioformat *fmt,
+					 struct usb_host_interface *alts)
+{
+	const struct snd_usb_implicit_fb_match *p;
+	unsigned int attr = fmt->ep_attr & USB_ENDPOINT_SYNCTYPE;
+
+	p = find_implicit_fb_entry(chip, playback_implicit_fb_quirks, alts);
+	if (p) {
+		switch (p->type) {
+		case IMPLICIT_FB_GENERIC:
+			return add_generic_implicit_fb(chip, fmt, alts);
+		case IMPLICIT_FB_NONE:
+			return 0; /* No quirk */
+		case IMPLICIT_FB_FIXED:
+			return add_implicit_fb_sync_ep(chip, fmt, p->ep_num, 0,
+						       p->iface, NULL);
+		}
+	}
+
+	/* Special handling for devices with capture quirks */
+	p = find_implicit_fb_entry(chip, capture_implicit_fb_quirks, alts);
+	if (p) {
+		switch (p->type) {
+		case IMPLICIT_FB_FIXED:
+			return 0; /* no quirk */
+		case IMPLICIT_FB_BOTH:
+			chip->quirk_flags |= QUIRK_FLAG_PLAYBACK_FIRST;
+			return add_generic_implicit_fb(chip, fmt, alts);
+		}
+	}
+
+	/* Generic UAC2 implicit feedback */
+	if (attr == USB_ENDPOINT_SYNC_ASYNC &&
+	    alts->desc.bInterfaceClass == USB_CLASS_AUDIO &&
+	    alts->desc.bInterfaceProtocol == UAC_VERSION_2 &&
+	    alts->desc.bNumEndpoints == 1) {
+		if (add_generic_uac2_implicit_fb(chip, fmt,
+						 alts->desc.bInterfaceNumber + 1,
+						 alts->desc.bAlternateSetting))
+			return 1;
+	}
+
+	/* Roland/BOSS implicit feedback with vendor spec class */
+	if (USB_ID_VENDOR(chip->usb_id) == 0x0582) {
+		if (add_roland_implicit_fb(chip, fmt, alts) > 0)
+			return 1;
+	}
+
+	/* Pioneer devices with vendor spec class */
+	if (is_pioneer_implicit_fb(chip, alts)) {
+		chip->quirk_flags |= QUIRK_FLAG_PLAYBACK_FIRST;
+		return add_implicit_fb_sync_ep(chip, fmt,
+					       get_endpoint(alts, 1)->bEndpointAddress,
+					       1, alts->desc.bInterfaceNumber,
+					       alts);
+	}
+
+	/* Try the generic implicit fb if available */
+	if (chip->generic_implicit_fb ||
+	    (chip->quirk_flags & QUIRK_FLAG_GENERIC_IMPLICIT_FB))
+		return add_generic_implicit_fb(chip, fmt, alts);
+
+	/* No quirk */
+	return 0;
+}
+
+/* same for capture, but only handling FIXED entry */
+static int audioformat_capture_quirk(struct snd_usb_audio *chip,
+				     struct audioformat *fmt,
+				     struct usb_host_interface *alts)
+{
+	const struct snd_usb_implicit_fb_match *p;
+
+	p = find_implicit_fb_entry(chip, capture_implicit_fb_quirks, alts);
+	if (p && (p->type == IMPLICIT_FB_FIXED || p->type == IMPLICIT_FB_BOTH))
+		return add_implicit_fb_sync_ep(chip, fmt, p->ep_num, 0,
+					       p->iface, NULL);
+
+	/* Roland/BOSS need full-duplex streams */
+	if (USB_ID_VENDOR(chip->usb_id) == 0x0582) {
+		if (add_roland_capture_quirk(chip, fmt, alts) > 0)
+			return 1;
+	}
+
+	if (is_pioneer_implicit_fb(chip, alts))
+		return 1; /* skip the quirk, also don't handle generic sync EP */
+	return 0;
+}
+
+/*
+ * Parse altset and set up implicit feedback endpoint on the audioformat
+ */
+int snd_usb_parse_implicit_fb_quirk(struct snd_usb_audio *chip,
+				    struct audioformat *fmt,
+				    struct usb_host_interface *alts)
+{
+	if (chip->quirk_flags & QUIRK_FLAG_SKIP_IMPLICIT_FB)
+		return 0;
+	if (fmt->endpoint & USB_DIR_IN)
+		return audioformat_capture_quirk(chip, fmt, alts);
+	else
+		return audioformat_implicit_fb_quirk(chip, fmt, alts);
+}
+
+/*
+ * Return the score of matching two audioformats.
+ * Veto the audioformat if:
+ * - It has no channels for some reason.
+ * - Requested PCM format is not supported.
+ * - Requested sample rate is not supported.
+ */
+static int match_endpoint_audioformats(struct snd_usb_substream *subs,
+				       const struct audioformat *fp,
+				       int rate, int channels,
+				       snd_pcm_format_t pcm_format)
+{
+	int i, score;
+
+	if (fp->channels < 1)
+		return 0;
+
+	if (!(fp->formats & pcm_format_to_bits(pcm_format)))
+		return 0;
+
+	if (fp->rates & SNDRV_PCM_RATE_CONTINUOUS) {
+		if (rate < fp->rate_min || rate > fp->rate_max)
+			return 0;
+	} else {
+		for (i = 0; i < fp->nr_rates; i++) {
+			if (fp->rate_table[i] == rate)
+				break;
+		}
+		if (i >= fp->nr_rates)
+			return 0;
+	}
+
+	score = 1;
+	if (fp->channels == channels)
+		score++;
+
+	return score;
+}
+
+static struct snd_usb_substream *
+find_matching_substream(struct snd_usb_audio *chip, int stream, int ep_num,
+			int fmt_type)
+{
+	struct snd_usb_stream *as;
+	struct snd_usb_substream *subs;
+
+	list_for_each_entry(as, &chip->pcm_list, list) {
+		subs = &as->substream[stream];
+		if (as->fmt_type == fmt_type && subs->ep_num == ep_num)
+			return subs;
+	}
+
+	return NULL;
+}
+
+/*
+ * Return the audioformat that is suitable for the implicit fb
+ */
+const struct audioformat *
+snd_usb_find_implicit_fb_sync_format(struct snd_usb_audio *chip,
+				     const struct audioformat *target,
+				     const struct snd_pcm_hw_params *params,
+				     int stream,
+				     bool *fixed_rate)
+{
+	struct snd_usb_substream *subs;
+	const struct audioformat *fp, *sync_fmt = NULL;
+	int score, high_score;
+
+	/* Use the original audioformat as fallback for the shared altset */
+	if (target->iface == target->sync_iface &&
+	    target->altsetting == target->sync_altsetting)
+		sync_fmt = target;
+
+	subs = find_matching_substream(chip, stream, target->sync_ep,
+				       target->fmt_type);
+	if (!subs)
+		goto end;
+
+	high_score = 0;
+	list_for_each_entry(fp, &subs->fmt_list, list) {
+		score = match_endpoint_audioformats(subs, fp,
+						    params_rate(params),
+						    params_channels(params),
+						    params_format(params));
+		if (score > high_score) {
+			sync_fmt = fp;
+			high_score = score;
+		}
+	}
+
+ end:
+	if (fixed_rate)
+		*fixed_rate = snd_usb_pcm_has_fixed_rate(subs);
+	return sync_fmt;
+}
+