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, 213 insertions, 0 deletions

diff --git a/drivers/usb/gadget/config.c b/drivers/usb/gadget/config.c
new file mode 100644
index 000000000..256364d4b
--- /dev/null
+++ b/drivers/usb/gadget/config.c
@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * usb/gadget/config.c -- simplify building config descriptors
+ *
+ * Copyright (C) 2003 David Brownell
+ */
+
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/string.h>
+#include <linux/device.h>
+
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/composite.h>
+#include <linux/usb/otg.h>
+
+/**
+ * usb_descriptor_fillbuf - fill buffer with descriptors
+ * @buf: Buffer to be filled
+ * @buflen: Size of buf
+ * @src: Array of descriptor pointers, terminated by null pointer.
+ *
+ * Copies descriptors into the buffer, returning the length or a
+ * negative error code if they can't all be copied.  Useful when
+ * assembling descriptors for an associated set of interfaces used
+ * as part of configuring a composite device; or in other cases where
+ * sets of descriptors need to be marshaled.
+ */
+int
+usb_descriptor_fillbuf(void *buf, unsigned buflen,
+		const struct usb_descriptor_header **src)
+{
+	u8	*dest = buf;
+
+	if (!src)
+		return -EINVAL;
+
+	/* fill buffer from src[] until null descriptor ptr */
+	for (; NULL != *src; src++) {
+		unsigned		len = (*src)->bLength;
+
+		if (len > buflen)
+			return -EINVAL;
+		memcpy(dest, *src, len);
+		buflen -= len;
+		dest += len;
+	}
+	return dest - (u8 *)buf;
+}
+EXPORT_SYMBOL_GPL(usb_descriptor_fillbuf);
+
+/**
+ * usb_copy_descriptors - copy a vector of USB descriptors
+ * @src: null-terminated vector to copy
+ * Context: initialization code, which may sleep
+ *
+ * This makes a copy of a vector of USB descriptors.  Its primary use
+ * is to support usb_function objects which can have multiple copies,
+ * each needing different descriptors.  Functions may have static
+ * tables of descriptors, which are used as templates and customized
+ * with identifiers (for interfaces, strings, endpoints, and more)
+ * as needed by a given function instance.
+ */
+struct usb_descriptor_header **
+usb_copy_descriptors(struct usb_descriptor_header **src)
+{
+	struct usb_descriptor_header **tmp;
+	unsigned bytes;
+	unsigned n_desc;
+	void *mem;
+	struct usb_descriptor_header **ret;
+
+	/* count descriptors and their sizes; then add vector size */
+	for (bytes = 0, n_desc = 0, tmp = src; *tmp; tmp++, n_desc++)
+		bytes += (*tmp)->bLength;
+	bytes += (n_desc + 1) * sizeof(*tmp);
+
+	mem = kmalloc(bytes, GFP_KERNEL);
+	if (!mem)
+		return NULL;
+
+	/* fill in pointers starting at "tmp",
+	 * to descriptors copied starting at "mem";
+	 * and return "ret"
+	 */
+	tmp = mem;
+	ret = mem;
+	mem += (n_desc + 1) * sizeof(*tmp);
+	while (*src) {
+		memcpy(mem, *src, (*src)->bLength);
+		*tmp = mem;
+		tmp++;
+		mem += (*src)->bLength;
+		src++;
+	}
+	*tmp = NULL;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_copy_descriptors);
+
+int usb_assign_descriptors(struct usb_function *f,
+		struct usb_descriptor_header **fs,
+		struct usb_descriptor_header **hs,
+		struct usb_descriptor_header **ss,
+		struct usb_descriptor_header **ssp)
+{
+	/* super-speed-plus descriptor falls back to super-speed one,
+	 * if such a descriptor was provided, thus avoiding a NULL
+	 * pointer dereference if a 5gbps capable gadget is used with
+	 * a 10gbps capable config (device port + cable + host port)
+	 */
+	if (!ssp)
+		ssp = ss;
+
+	if (fs) {
+		f->fs_descriptors = usb_copy_descriptors(fs);
+		if (!f->fs_descriptors)
+			goto err;
+	}
+	if (hs) {
+		f->hs_descriptors = usb_copy_descriptors(hs);
+		if (!f->hs_descriptors)
+			goto err;
+	}
+	if (ss) {
+		f->ss_descriptors = usb_copy_descriptors(ss);
+		if (!f->ss_descriptors)
+			goto err;
+	}
+	if (ssp) {
+		f->ssp_descriptors = usb_copy_descriptors(ssp);
+		if (!f->ssp_descriptors)
+			goto err;
+	}
+	return 0;
+err:
+	usb_free_all_descriptors(f);
+	return -ENOMEM;
+}
+EXPORT_SYMBOL_GPL(usb_assign_descriptors);
+
+void usb_free_all_descriptors(struct usb_function *f)
+{
+	usb_free_descriptors(f->fs_descriptors);
+	f->fs_descriptors = NULL;
+	usb_free_descriptors(f->hs_descriptors);
+	f->hs_descriptors = NULL;
+	usb_free_descriptors(f->ss_descriptors);
+	f->ss_descriptors = NULL;
+	usb_free_descriptors(f->ssp_descriptors);
+	f->ssp_descriptors = NULL;
+}
+EXPORT_SYMBOL_GPL(usb_free_all_descriptors);
+
+struct usb_descriptor_header *usb_otg_descriptor_alloc(
+				struct usb_gadget *gadget)
+{
+	struct usb_descriptor_header *otg_desc;
+	unsigned length = 0;
+
+	if (gadget->otg_caps && (gadget->otg_caps->otg_rev >= 0x0200))
+		length = sizeof(struct usb_otg20_descriptor);
+	else
+		length = sizeof(struct usb_otg_descriptor);
+
+	otg_desc = kzalloc(length, GFP_KERNEL);
+	return otg_desc;
+}
+EXPORT_SYMBOL_GPL(usb_otg_descriptor_alloc);
+
+int usb_otg_descriptor_init(struct usb_gadget *gadget,
+		struct usb_descriptor_header *otg_desc)
+{
+	struct usb_otg_descriptor *otg1x_desc;
+	struct usb_otg20_descriptor *otg20_desc;
+	struct usb_otg_caps *otg_caps = gadget->otg_caps;
+	u8 otg_attributes = 0;
+
+	if (!otg_desc)
+		return -EINVAL;
+
+	if (otg_caps && otg_caps->otg_rev) {
+		if (otg_caps->hnp_support)
+			otg_attributes |= USB_OTG_HNP;
+		if (otg_caps->srp_support)
+			otg_attributes |= USB_OTG_SRP;
+		if (otg_caps->adp_support && (otg_caps->otg_rev >= 0x0200))
+			otg_attributes |= USB_OTG_ADP;
+	} else {
+		otg_attributes = USB_OTG_SRP | USB_OTG_HNP;
+	}
+
+	if (otg_caps && (otg_caps->otg_rev >= 0x0200)) {
+		otg20_desc = (struct usb_otg20_descriptor *)otg_desc;
+		otg20_desc->bLength = sizeof(struct usb_otg20_descriptor);
+		otg20_desc->bDescriptorType = USB_DT_OTG;
+		otg20_desc->bmAttributes = otg_attributes;
+		otg20_desc->bcdOTG = cpu_to_le16(otg_caps->otg_rev);
+	} else {
+		otg1x_desc = (struct usb_otg_descriptor *)otg_desc;
+		otg1x_desc->bLength = sizeof(struct usb_otg_descriptor);
+		otg1x_desc->bDescriptorType = USB_DT_OTG;
+		otg1x_desc->bmAttributes = otg_attributes;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_descriptor_init);