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, 576 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_proc.c b/drivers/scsi/scsi_proc.c
new file mode 100644
index 000000000..1799dcae7
--- /dev/null
+++ b/drivers/scsi/scsi_proc.c
@@ -0,0 +1,576 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/drivers/scsi/scsi_proc.c
+ *
+ * The functions in this file provide an interface between
+ * the PROC file system and the SCSI device drivers
+ * It is mainly used for debugging, statistics and to pass 
+ * information directly to the lowlevel driver.
+ *
+ * (c) 1995 Michael Neuffer neuffer@goofy.zdv.uni-mainz.de 
+ * Version: 0.99.8   last change: 95/09/13
+ * 
+ * generic command parser provided by: 
+ * Andreas Heilwagen <crashcar@informatik.uni-koblenz.de>
+ *
+ * generic_proc_info() support of xxxx_info() by:
+ * Michael A. Griffith <grif@acm.org>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/errno.h>
+#include <linux/blkdev.h>
+#include <linux/seq_file.h>
+#include <linux/mutex.h>
+#include <linux/gfp.h>
+#include <linux/uaccess.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_transport.h>
+
+#include "scsi_priv.h"
+#include "scsi_logging.h"
+
+
+/* 4K page size, but our output routines, use some slack for overruns */
+#define PROC_BLOCK_SIZE (3*1024)
+
+static struct proc_dir_entry *proc_scsi;
+
+/* Protects scsi_proc_list */
+static DEFINE_MUTEX(global_host_template_mutex);
+static LIST_HEAD(scsi_proc_list);
+
+/**
+ * struct scsi_proc_entry - (host template, SCSI proc dir) association
+ * @entry: entry in scsi_proc_list.
+ * @sht: SCSI host template associated with the procfs directory.
+ * @proc_dir: procfs directory associated with the SCSI host template.
+ * @present: Number of SCSI hosts instantiated for @sht.
+ */
+struct scsi_proc_entry {
+	struct list_head	entry;
+	const struct scsi_host_template *sht;
+	struct proc_dir_entry	*proc_dir;
+	unsigned int		present;
+};
+
+static ssize_t proc_scsi_host_write(struct file *file, const char __user *buf,
+                           size_t count, loff_t *ppos)
+{
+	struct Scsi_Host *shost = pde_data(file_inode(file));
+	ssize_t ret = -ENOMEM;
+	char *page;
+    
+	if (count > PROC_BLOCK_SIZE)
+		return -EOVERFLOW;
+
+	if (!shost->hostt->write_info)
+		return -EINVAL;
+
+	page = (char *)__get_free_page(GFP_KERNEL);
+	if (page) {
+		ret = -EFAULT;
+		if (copy_from_user(page, buf, count))
+			goto out;
+		ret = shost->hostt->write_info(shost, page, count);
+	}
+out:
+	free_page((unsigned long)page);
+	return ret;
+}
+
+static int proc_scsi_show(struct seq_file *m, void *v)
+{
+	struct Scsi_Host *shost = m->private;
+	return shost->hostt->show_info(m, shost);
+}
+
+static int proc_scsi_host_open(struct inode *inode, struct file *file)
+{
+	return single_open_size(file, proc_scsi_show, pde_data(inode),
+				4 * PAGE_SIZE);
+}
+
+static struct scsi_proc_entry *
+__scsi_lookup_proc_entry(const struct scsi_host_template *sht)
+{
+	struct scsi_proc_entry *e;
+
+	lockdep_assert_held(&global_host_template_mutex);
+
+	list_for_each_entry(e, &scsi_proc_list, entry)
+		if (e->sht == sht)
+			return e;
+
+	return NULL;
+}
+
+static struct scsi_proc_entry *
+scsi_lookup_proc_entry(const struct scsi_host_template *sht)
+{
+	struct scsi_proc_entry *e;
+
+	mutex_lock(&global_host_template_mutex);
+	e = __scsi_lookup_proc_entry(sht);
+	mutex_unlock(&global_host_template_mutex);
+
+	return e;
+}
+
+/**
+ * scsi_template_proc_dir() - returns the procfs dir for a SCSI host template
+ * @sht: SCSI host template pointer.
+ */
+struct proc_dir_entry *
+scsi_template_proc_dir(const struct scsi_host_template *sht)
+{
+	struct scsi_proc_entry *e = scsi_lookup_proc_entry(sht);
+
+	return e ? e->proc_dir : NULL;
+}
+EXPORT_SYMBOL_GPL(scsi_template_proc_dir);
+
+static const struct proc_ops proc_scsi_ops = {
+	.proc_open	= proc_scsi_host_open,
+	.proc_release	= single_release,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_write	= proc_scsi_host_write
+};
+
+/**
+ * scsi_proc_hostdir_add - Create directory in /proc for a scsi host
+ * @sht: owner of this directory
+ *
+ * Sets sht->proc_dir to the new directory.
+ */
+int scsi_proc_hostdir_add(const struct scsi_host_template *sht)
+{
+	struct scsi_proc_entry *e;
+	int ret;
+
+	if (!sht->show_info)
+		return 0;
+
+	mutex_lock(&global_host_template_mutex);
+	e = __scsi_lookup_proc_entry(sht);
+	if (!e) {
+		e = kzalloc_obj(*e);
+		if (!e) {
+			ret = -ENOMEM;
+			goto unlock;
+		}
+	}
+	if (e->present++)
+		goto success;
+	e->proc_dir = proc_mkdir(sht->proc_name, proc_scsi);
+	if (!e->proc_dir) {
+		printk(KERN_ERR "%s: proc_mkdir failed for %s\n", __func__,
+		       sht->proc_name);
+		ret = -ENOMEM;
+		goto unlock;
+	}
+	e->sht = sht;
+	list_add_tail(&e->entry, &scsi_proc_list);
+success:
+	e = NULL;
+	ret = 0;
+unlock:
+	mutex_unlock(&global_host_template_mutex);
+
+	kfree(e);
+	return ret;
+}
+
+/**
+ * scsi_proc_hostdir_rm - remove directory in /proc for a scsi host
+ * @sht: owner of directory
+ */
+void scsi_proc_hostdir_rm(const struct scsi_host_template *sht)
+{
+	struct scsi_proc_entry *e;
+
+	if (!sht->show_info)
+		return;
+
+	mutex_lock(&global_host_template_mutex);
+	e = __scsi_lookup_proc_entry(sht);
+	if (e && !--e->present) {
+		remove_proc_entry(sht->proc_name, proc_scsi);
+		list_del(&e->entry);
+		kfree(e);
+	}
+	mutex_unlock(&global_host_template_mutex);
+}
+
+
+/**
+ * scsi_proc_host_add - Add entry for this host to appropriate /proc dir
+ * @shost: host to add
+ */
+void scsi_proc_host_add(struct Scsi_Host *shost)
+{
+	const struct scsi_host_template *sht = shost->hostt;
+	struct scsi_proc_entry *e;
+	struct proc_dir_entry *p;
+	char name[10];
+
+	if (!sht->show_info)
+		return;
+
+	e = scsi_lookup_proc_entry(sht);
+	if (!e)
+		goto err;
+
+	sprintf(name,"%d", shost->host_no);
+	p = proc_create_data(name, S_IRUGO | S_IWUSR, e->proc_dir,
+			     &proc_scsi_ops, shost);
+	if (!p)
+		goto err;
+	return;
+
+err:
+	shost_printk(KERN_ERR, shost,
+		     "%s: Failed to register host (%s failed)\n", __func__,
+		     e ? "proc_create_data()" : "scsi_proc_hostdir_add()");
+}
+
+/**
+ * scsi_proc_host_rm - remove this host's entry from /proc
+ * @shost: which host
+ */
+void scsi_proc_host_rm(struct Scsi_Host *shost)
+{
+	const struct scsi_host_template *sht = shost->hostt;
+	struct scsi_proc_entry *e;
+	char name[10];
+
+	if (!sht->show_info)
+		return;
+
+	e = scsi_lookup_proc_entry(sht);
+	if (!e)
+		return;
+
+	sprintf(name,"%d", shost->host_no);
+	remove_proc_entry(name, e->proc_dir);
+}
+/**
+ * proc_print_scsidevice - return data about this host
+ * @dev: A scsi device
+ * @data: &struct seq_file to output to.
+ *
+ * Description: prints Host, Channel, Id, Lun, Vendor, Model, Rev, Type,
+ * and revision.
+ */
+static int proc_print_scsidevice(struct device *dev, void *data)
+{
+	struct scsi_device *sdev;
+	struct seq_file *s = data;
+	int i;
+
+	if (!scsi_is_sdev_device(dev))
+		goto out;
+
+	sdev = to_scsi_device(dev);
+	seq_printf(s,
+		"Host: scsi%d Channel: %02d Id: %02d Lun: %02llu\n  Vendor: ",
+		sdev->host->host_no, sdev->channel, sdev->id, sdev->lun);
+	for (i = 0; i < 8; i++) {
+		if (sdev->vendor[i] >= 0x20)
+			seq_putc(s, sdev->vendor[i]);
+		else
+			seq_putc(s, ' ');
+	}
+
+	seq_puts(s, " Model: ");
+	for (i = 0; i < 16; i++) {
+		if (sdev->model[i] >= 0x20)
+			seq_putc(s, sdev->model[i]);
+		else
+			seq_putc(s, ' ');
+	}
+
+	seq_puts(s, " Rev: ");
+	for (i = 0; i < 4; i++) {
+		if (sdev->rev[i] >= 0x20)
+			seq_putc(s, sdev->rev[i]);
+		else
+			seq_putc(s, ' ');
+	}
+
+	seq_putc(s, '\n');
+
+	seq_printf(s, "  Type:   %s ", scsi_device_type(sdev->type));
+	seq_printf(s, "               ANSI  SCSI revision: %02x",
+			sdev->scsi_level - (sdev->scsi_level > 1));
+	if (sdev->scsi_level == 2)
+		seq_puts(s, " CCS\n");
+	else
+		seq_putc(s, '\n');
+
+out:
+	return 0;
+}
+
+/**
+ * scsi_add_single_device - Respond to user request to probe for/add device
+ * @host: user-supplied decimal integer
+ * @channel: user-supplied decimal integer
+ * @id: user-supplied decimal integer
+ * @lun: user-supplied decimal integer
+ *
+ * Description: called by writing "scsi add-single-device" to /proc/scsi/scsi.
+ *
+ * does scsi_host_lookup() and either user_scan() if that transport
+ * type supports it, or else scsi_scan_host_selected()
+ *
+ * Note: this seems to be aimed exclusively at SCSI parallel busses.
+ */
+
+static int scsi_add_single_device(uint host, uint channel, uint id, uint lun)
+{
+	struct Scsi_Host *shost;
+	int error = -ENXIO;
+
+	shost = scsi_host_lookup(host);
+	if (!shost)
+		return error;
+
+	if (shost->transportt->user_scan)
+		error = shost->transportt->user_scan(shost, channel, id, lun);
+	else
+		error = scsi_scan_host_selected(shost, channel, id, lun,
+						SCSI_SCAN_MANUAL);
+	scsi_host_put(shost);
+	return error;
+}
+
+/**
+ * scsi_remove_single_device - Respond to user request to remove a device
+ * @host: user-supplied decimal integer
+ * @channel: user-supplied decimal integer
+ * @id: user-supplied decimal integer
+ * @lun: user-supplied decimal integer
+ *
+ * Description: called by writing "scsi remove-single-device" to
+ * /proc/scsi/scsi.  Does a scsi_device_lookup() and scsi_remove_device()
+ */
+static int scsi_remove_single_device(uint host, uint channel, uint id, uint lun)
+{
+	struct scsi_device *sdev;
+	struct Scsi_Host *shost;
+	int error = -ENXIO;
+
+	shost = scsi_host_lookup(host);
+	if (!shost)
+		return error;
+	sdev = scsi_device_lookup(shost, channel, id, lun);
+	if (sdev) {
+		scsi_remove_device(sdev);
+		scsi_device_put(sdev);
+		error = 0;
+	}
+
+	scsi_host_put(shost);
+	return error;
+}
+
+/**
+ * proc_scsi_write - handle writes to /proc/scsi/scsi
+ * @file: not used
+ * @buf: buffer to write
+ * @length: length of buf, at most PAGE_SIZE
+ * @ppos: not used
+ *
+ * Description: this provides a legacy mechanism to add or remove devices by
+ * Host, Channel, ID, and Lun.  To use,
+ * "echo 'scsi add-single-device 0 1 2 3' > /proc/scsi/scsi" or
+ * "echo 'scsi remove-single-device 0 1 2 3' > /proc/scsi/scsi" with
+ * "0 1 2 3" replaced by the Host, Channel, Id, and Lun.
+ *
+ * Note: this seems to be aimed at parallel SCSI. Most modern busses (USB,
+ * SATA, Firewire, Fibre Channel, etc) dynamically assign these values to
+ * provide a unique identifier and nothing more.
+ */
+
+
+static ssize_t proc_scsi_write(struct file *file, const char __user *buf,
+			       size_t length, loff_t *ppos)
+{
+	int host, channel, id, lun;
+	char *buffer, *end, *p;
+	int err;
+
+	if (!buf || length > PAGE_SIZE)
+		return -EINVAL;
+
+	buffer = (char *)__get_free_page(GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	err = -EFAULT;
+	if (copy_from_user(buffer, buf, length))
+		goto out;
+
+	err = -EINVAL;
+	if (length < PAGE_SIZE) {
+		end = buffer + length;
+		*end = '\0';
+	} else {
+		end = buffer + PAGE_SIZE - 1;
+		if (*end)
+			goto out;
+	}
+
+	/*
+	 * Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
+	 * with  "0 1 2 3" replaced by your "Host Channel Id Lun".
+	 */
+	if (!strncmp("scsi add-single-device", buffer, 22)) {
+		p = buffer + 23;
+
+		host    = (p     < end) ? simple_strtoul(p, &p, 0) : 0;
+		channel = (p + 1 < end) ? simple_strtoul(p + 1, &p, 0) : 0;
+		id      = (p + 1 < end) ? simple_strtoul(p + 1, &p, 0) : 0;
+		lun     = (p + 1 < end) ? simple_strtoul(p + 1, &p, 0) : 0;
+
+		err = scsi_add_single_device(host, channel, id, lun);
+
+	/*
+	 * Usage: echo "scsi remove-single-device 0 1 2 3" >/proc/scsi/scsi
+	 * with  "0 1 2 3" replaced by your "Host Channel Id Lun".
+	 */
+	} else if (!strncmp("scsi remove-single-device", buffer, 25)) {
+		p = buffer + 26;
+
+		host    = (p     < end) ? simple_strtoul(p, &p, 0) : 0;
+		channel = (p + 1 < end) ? simple_strtoul(p + 1, &p, 0) : 0;
+		id      = (p + 1 < end) ? simple_strtoul(p + 1, &p, 0) : 0;
+		lun     = (p + 1 < end) ? simple_strtoul(p + 1, &p, 0) : 0;
+
+		err = scsi_remove_single_device(host, channel, id, lun);
+	}
+
+	/*
+	 * convert success returns so that we return the 
+	 * number of bytes consumed.
+	 */
+	if (!err)
+		err = length;
+
+ out:
+	free_page((unsigned long)buffer);
+	return err;
+}
+
+static inline struct device *next_scsi_device(struct device *start)
+{
+	struct device *next = bus_find_next_device(&scsi_bus_type, start);
+
+	put_device(start);
+	return next;
+}
+
+static void *scsi_seq_start(struct seq_file *sfile, loff_t *pos)
+{
+	struct device *dev = NULL;
+	loff_t n = *pos;
+
+	while ((dev = next_scsi_device(dev))) {
+		if (!n--)
+			break;
+		sfile->private++;
+	}
+	return dev;
+}
+
+static void *scsi_seq_next(struct seq_file *sfile, void *v, loff_t *pos)
+{
+	(*pos)++;
+	sfile->private++;
+	return next_scsi_device(v);
+}
+
+static void scsi_seq_stop(struct seq_file *sfile, void *v)
+{
+	put_device(v);
+}
+
+static int scsi_seq_show(struct seq_file *sfile, void *dev)
+{
+	if (!sfile->private)
+		seq_puts(sfile, "Attached devices:\n");
+
+	return proc_print_scsidevice(dev, sfile);
+}
+
+static const struct seq_operations scsi_seq_ops = {
+	.start	= scsi_seq_start,
+	.next	= scsi_seq_next,
+	.stop	= scsi_seq_stop,
+	.show	= scsi_seq_show
+};
+
+/**
+ * proc_scsi_open - glue function
+ * @inode: not used
+ * @file: passed to single_open()
+ *
+ * Associates proc_scsi_show with this file
+ */
+static int proc_scsi_open(struct inode *inode, struct file *file)
+{
+	/*
+	 * We don't really need this for the write case but it doesn't
+	 * harm either.
+	 */
+	return seq_open(file, &scsi_seq_ops);
+}
+
+static const struct proc_ops scsi_scsi_proc_ops = {
+	.proc_open	= proc_scsi_open,
+	.proc_read	= seq_read,
+	.proc_write	= proc_scsi_write,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= seq_release,
+};
+
+/**
+ * scsi_init_procfs - create scsi and scsi/scsi in procfs
+ */
+int __init scsi_init_procfs(void)
+{
+	struct proc_dir_entry *pde;
+
+	proc_scsi = proc_mkdir("scsi", NULL);
+	if (!proc_scsi)
+		goto err1;
+
+	pde = proc_create("scsi/scsi", 0, NULL, &scsi_scsi_proc_ops);
+	if (!pde)
+		goto err2;
+
+	return 0;
+
+err2:
+	remove_proc_entry("scsi", NULL);
+err1:
+	return -ENOMEM;
+}
+
+/**
+ * scsi_exit_procfs - Remove scsi/scsi and scsi from procfs
+ */
+void scsi_exit_procfs(void)
+{
+	remove_proc_entry("scsi/scsi", NULL);
+	remove_proc_entry("scsi", NULL);
+}