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, 411 insertions, 0 deletions

diff --git a/drivers/block/z2ram.c b/drivers/block/z2ram.c
new file mode 100644
index 000000000..b216cba1c
--- /dev/null
+++ b/drivers/block/z2ram.c
@@ -0,0 +1,411 @@
+/*
+** z2ram - Amiga pseudo-driver to access 16bit-RAM in ZorroII space
+**         as a block device, to be used as a RAM disk or swap space
+** 
+** Copyright (C) 1994 by Ingo Wilken (Ingo.Wilken@informatik.uni-oldenburg.de)
+**
+** ++Geert: support for zorro_unused_z2ram, better range checking
+** ++roman: translate accesses via an array
+** ++Milan: support for ChipRAM usage
+** ++yambo: converted to 2.0 kernel
+** ++yambo: modularized and support added for 3 minor devices including:
+**          MAJOR  MINOR  DESCRIPTION
+**          -----  -----  ----------------------------------------------
+**          37     0       Use Zorro II and Chip ram
+**          37     1       Use only Zorro II ram
+**          37     2       Use only Chip ram
+**          37     4-7     Use memory list entry 1-4 (first is 0)
+** ++jskov: support for 1-4th memory list entry.
+**
+** Permission to use, copy, modify, and distribute this software and its
+** documentation for any purpose and without fee is hereby granted, provided
+** that the above copyright notice appear in all copies and that both that
+** copyright notice and this permission notice appear in supporting
+** documentation.  This software is provided "as is" without express or
+** implied warranty.
+*/
+
+#define DEVICE_NAME "Z2RAM"
+
+#include <linux/major.h>
+#include <linux/vmalloc.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/blk-mq.h>
+#include <linux/bitops.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/pgtable.h>
+
+#include <asm/setup.h>
+#include <asm/amigahw.h>
+
+#include <linux/zorro.h>
+
+#define Z2MINOR_COMBINED      (0)
+#define Z2MINOR_Z2ONLY        (1)
+#define Z2MINOR_CHIPONLY      (2)
+#define Z2MINOR_MEMLIST1      (4)
+#define Z2MINOR_MEMLIST2      (5)
+#define Z2MINOR_MEMLIST3      (6)
+#define Z2MINOR_MEMLIST4      (7)
+#define Z2MINOR_COUNT         (8)	/* Move this down when adding a new minor */
+
+#define Z2RAM_CHUNK1024       ( Z2RAM_CHUNKSIZE >> 10 )
+
+static DEFINE_MUTEX(z2ram_mutex);
+static u_long *z2ram_map = NULL;
+static u_long z2ram_size = 0;
+static int z2_count = 0;
+static int chip_count = 0;
+static int list_count = 0;
+static int current_device = -1;
+
+static DEFINE_SPINLOCK(z2ram_lock);
+
+static struct gendisk *z2ram_gendisk[Z2MINOR_COUNT];
+
+static blk_status_t z2_queue_rq(struct blk_mq_hw_ctx *hctx,
+				const struct blk_mq_queue_data *bd)
+{
+	struct request *req = bd->rq;
+	unsigned long start = blk_rq_pos(req) << 9;
+	unsigned long len = blk_rq_cur_bytes(req);
+
+	blk_mq_start_request(req);
+
+	if (start + len > z2ram_size) {
+		pr_err(DEVICE_NAME ": bad access: block=%llu, "
+		       "count=%u\n",
+		       (unsigned long long)blk_rq_pos(req),
+		       blk_rq_cur_sectors(req));
+		return BLK_STS_IOERR;
+	}
+
+	spin_lock_irq(&z2ram_lock);
+
+	while (len) {
+		unsigned long addr = start & Z2RAM_CHUNKMASK;
+		unsigned long size = Z2RAM_CHUNKSIZE - addr;
+		void *buffer = bio_data(req->bio);
+
+		if (len < size)
+			size = len;
+		addr += z2ram_map[start >> Z2RAM_CHUNKSHIFT];
+		if (rq_data_dir(req) == READ)
+			memcpy(buffer, (char *)addr, size);
+		else
+			memcpy((char *)addr, buffer, size);
+		start += size;
+		len -= size;
+	}
+
+	spin_unlock_irq(&z2ram_lock);
+	blk_mq_end_request(req, BLK_STS_OK);
+	return BLK_STS_OK;
+}
+
+static void get_z2ram(void)
+{
+	int i;
+
+	for (i = 0; i < Z2RAM_SIZE / Z2RAM_CHUNKSIZE; i++) {
+		if (test_bit(i, zorro_unused_z2ram)) {
+			z2_count++;
+			z2ram_map[z2ram_size++] =
+			    (unsigned long)ZTWO_VADDR(Z2RAM_START) +
+			    (i << Z2RAM_CHUNKSHIFT);
+			clear_bit(i, zorro_unused_z2ram);
+		}
+	}
+
+	return;
+}
+
+static void get_chipram(void)
+{
+
+	while (amiga_chip_avail() > (Z2RAM_CHUNKSIZE * 4)) {
+		chip_count++;
+		z2ram_map[z2ram_size] =
+		    (u_long) amiga_chip_alloc(Z2RAM_CHUNKSIZE, "z2ram");
+
+		if (z2ram_map[z2ram_size] == 0) {
+			break;
+		}
+
+		z2ram_size++;
+	}
+
+	return;
+}
+
+static int z2_open(struct gendisk *disk, blk_mode_t mode)
+{
+	int device = disk->first_minor;
+	int max_z2_map = (Z2RAM_SIZE / Z2RAM_CHUNKSIZE) * sizeof(z2ram_map[0]);
+	int max_chip_map = (amiga_chip_size / Z2RAM_CHUNKSIZE) *
+	    sizeof(z2ram_map[0]);
+	int rc = -ENOMEM;
+
+	mutex_lock(&z2ram_mutex);
+	if (current_device != -1 && current_device != device) {
+		rc = -EBUSY;
+		goto err_out;
+	}
+
+	if (current_device == -1) {
+		z2_count = 0;
+		chip_count = 0;
+		list_count = 0;
+		z2ram_size = 0;
+
+		/* Use a specific list entry. */
+		if (device >= Z2MINOR_MEMLIST1 && device <= Z2MINOR_MEMLIST4) {
+			int index = device - Z2MINOR_MEMLIST1 + 1;
+			unsigned long size, paddr, vaddr;
+
+			if (index >= m68k_realnum_memory) {
+				printk(KERN_ERR DEVICE_NAME
+				       ": no such entry in z2ram_map\n");
+				goto err_out;
+			}
+
+			paddr = m68k_memory[index].addr;
+			size = m68k_memory[index].size & ~(Z2RAM_CHUNKSIZE - 1);
+
+#ifdef __powerpc__
+			/* FIXME: ioremap doesn't build correct memory tables. */
+			{
+				vfree(vmalloc(size));
+			}
+
+			vaddr = (unsigned long)ioremap_wt(paddr, size);
+
+#else
+			vaddr =
+			    (unsigned long)z_remap_nocache_nonser(paddr, size);
+#endif
+			z2ram_map =
+			    kmalloc_objs(z2ram_map[0], size / Z2RAM_CHUNKSIZE);
+			if (z2ram_map == NULL) {
+				printk(KERN_ERR DEVICE_NAME
+				       ": cannot get mem for z2ram_map\n");
+				goto err_out;
+			}
+
+			while (size) {
+				z2ram_map[z2ram_size++] = vaddr;
+				size -= Z2RAM_CHUNKSIZE;
+				vaddr += Z2RAM_CHUNKSIZE;
+				list_count++;
+			}
+
+			if (z2ram_size != 0)
+				printk(KERN_INFO DEVICE_NAME
+				       ": using %iK List Entry %d Memory\n",
+				       list_count * Z2RAM_CHUNK1024, index);
+		} else
+			switch (device) {
+			case Z2MINOR_COMBINED:
+
+				z2ram_map =
+				    kmalloc(max_z2_map + max_chip_map,
+					    GFP_KERNEL);
+				if (z2ram_map == NULL) {
+					printk(KERN_ERR DEVICE_NAME
+					       ": cannot get mem for z2ram_map\n");
+					goto err_out;
+				}
+
+				get_z2ram();
+				get_chipram();
+
+				if (z2ram_size != 0)
+					printk(KERN_INFO DEVICE_NAME
+					       ": using %iK Zorro II RAM and %iK Chip RAM (Total %dK)\n",
+					       z2_count * Z2RAM_CHUNK1024,
+					       chip_count * Z2RAM_CHUNK1024,
+					       (z2_count +
+						chip_count) * Z2RAM_CHUNK1024);
+
+				break;
+
+			case Z2MINOR_Z2ONLY:
+				z2ram_map = kmalloc(max_z2_map, GFP_KERNEL);
+				if (!z2ram_map)
+					goto err_out;
+
+				get_z2ram();
+
+				if (z2ram_size != 0)
+					printk(KERN_INFO DEVICE_NAME
+					       ": using %iK of Zorro II RAM\n",
+					       z2_count * Z2RAM_CHUNK1024);
+
+				break;
+
+			case Z2MINOR_CHIPONLY:
+				z2ram_map = kmalloc(max_chip_map, GFP_KERNEL);
+				if (!z2ram_map)
+					goto err_out;
+
+				get_chipram();
+
+				if (z2ram_size != 0)
+					printk(KERN_INFO DEVICE_NAME
+					       ": using %iK Chip RAM\n",
+					       chip_count * Z2RAM_CHUNK1024);
+
+				break;
+
+			default:
+				rc = -ENODEV;
+				goto err_out;
+
+				break;
+			}
+
+		if (z2ram_size == 0) {
+			printk(KERN_NOTICE DEVICE_NAME
+			       ": no unused ZII/Chip RAM found\n");
+			goto err_out_kfree;
+		}
+
+		current_device = device;
+		z2ram_size <<= Z2RAM_CHUNKSHIFT;
+		set_capacity(z2ram_gendisk[device], z2ram_size >> 9);
+	}
+
+	mutex_unlock(&z2ram_mutex);
+	return 0;
+
+err_out_kfree:
+	kfree(z2ram_map);
+err_out:
+	mutex_unlock(&z2ram_mutex);
+	return rc;
+}
+
+static void z2_release(struct gendisk *disk)
+{
+	mutex_lock(&z2ram_mutex);
+	if (current_device == -1) {
+		mutex_unlock(&z2ram_mutex);
+		return;
+	}
+	mutex_unlock(&z2ram_mutex);
+	/*
+	 * FIXME: unmap memory
+	 */
+}
+
+static const struct block_device_operations z2_fops = {
+	.owner = THIS_MODULE,
+	.open = z2_open,
+	.release = z2_release,
+};
+
+static struct blk_mq_tag_set tag_set;
+
+static const struct blk_mq_ops z2_mq_ops = {
+	.queue_rq = z2_queue_rq,
+};
+
+static int z2ram_register_disk(int minor)
+{
+	struct gendisk *disk;
+	int err;
+
+	disk = blk_mq_alloc_disk(&tag_set, NULL, NULL);
+	if (IS_ERR(disk))
+		return PTR_ERR(disk);
+
+	disk->major = Z2RAM_MAJOR;
+	disk->first_minor = minor;
+	disk->minors = 1;
+	disk->flags |= GENHD_FL_NO_PART;
+	disk->fops = &z2_fops;
+	if (minor)
+		sprintf(disk->disk_name, "z2ram%d", minor);
+	else
+		sprintf(disk->disk_name, "z2ram");
+
+	z2ram_gendisk[minor] = disk;
+	err = add_disk(disk);
+	if (err)
+		put_disk(disk);
+	return err;
+}
+
+static int __init z2_init(void)
+{
+	int ret, i;
+
+	if (!MACH_IS_AMIGA)
+		return -ENODEV;
+
+	if (register_blkdev(Z2RAM_MAJOR, DEVICE_NAME))
+		return -EBUSY;
+
+	tag_set.ops = &z2_mq_ops;
+	tag_set.nr_hw_queues = 1;
+	tag_set.nr_maps = 1;
+	tag_set.queue_depth = 16;
+	tag_set.numa_node = NUMA_NO_NODE;
+	ret = blk_mq_alloc_tag_set(&tag_set);
+	if (ret)
+		goto out_unregister_blkdev;
+
+	for (i = 0; i < Z2MINOR_COUNT; i++) {
+		ret = z2ram_register_disk(i);
+		if (ret && i == 0)
+			goto out_free_tagset;
+	}
+
+	return 0;
+
+out_free_tagset:
+	blk_mq_free_tag_set(&tag_set);
+out_unregister_blkdev:
+	unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
+	return ret;
+}
+
+static void __exit z2_exit(void)
+{
+	int i, j;
+
+	unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
+
+	for (i = 0; i < Z2MINOR_COUNT; i++) {
+		del_gendisk(z2ram_gendisk[i]);
+		put_disk(z2ram_gendisk[i]);
+	}
+	blk_mq_free_tag_set(&tag_set);
+
+	if (current_device != -1) {
+		i = 0;
+
+		for (j = 0; j < z2_count; j++) {
+			set_bit(i++, zorro_unused_z2ram);
+		}
+
+		for (j = 0; j < chip_count; j++) {
+			if (z2ram_map[i]) {
+				amiga_chip_free((void *)z2ram_map[i++]);
+			}
+		}
+
+		if (z2ram_map != NULL) {
+			kfree(z2ram_map);
+		}
+	}
+
+	return;
+}
+
+module_init(z2_init);
+module_exit(z2_exit);
+MODULE_DESCRIPTION("Amiga Zorro II ramdisk driver");
+MODULE_LICENSE("GPL");