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, 542 insertions, 0 deletions

diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
new file mode 100644
index 000000000..4d2e7b777
--- /dev/null
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -0,0 +1,542 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Interface to Linux block layer for MTD 'translation layers'.
+ *
+ * Copyright © 2003-2010 David Woodhouse <dwmw2@infradead.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/mtd/blktrans.h>
+#include <linux/mtd/mtd.h>
+#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
+#include <linux/blkpg.h>
+#include <linux/spinlock.h>
+#include <linux/hdreg.h>
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+
+#include "mtdcore.h"
+
+static LIST_HEAD(blktrans_majors);
+
+static void blktrans_dev_release(struct kref *kref)
+{
+	struct mtd_blktrans_dev *dev =
+		container_of(kref, struct mtd_blktrans_dev, ref);
+
+	put_disk(dev->disk);
+	blk_mq_free_tag_set(dev->tag_set);
+	kfree(dev->tag_set);
+	list_del(&dev->list);
+	kfree(dev);
+}
+
+static void blktrans_dev_put(struct mtd_blktrans_dev *dev)
+{
+	kref_put(&dev->ref, blktrans_dev_release);
+}
+
+
+static blk_status_t do_blktrans_request(struct mtd_blktrans_ops *tr,
+			       struct mtd_blktrans_dev *dev,
+			       struct request *req)
+{
+	struct req_iterator iter;
+	struct bio_vec bvec;
+	unsigned long block, nsect;
+	char *buf;
+
+	block = blk_rq_pos(req) << 9 >> tr->blkshift;
+	nsect = blk_rq_cur_bytes(req) >> tr->blkshift;
+
+	switch (req_op(req)) {
+	case REQ_OP_FLUSH:
+		if (tr->flush(dev))
+			return BLK_STS_IOERR;
+		return BLK_STS_OK;
+	case REQ_OP_DISCARD:
+		if (tr->discard(dev, block, nsect))
+			return BLK_STS_IOERR;
+		return BLK_STS_OK;
+	case REQ_OP_READ:
+		buf = kmap(bio_page(req->bio)) + bio_offset(req->bio);
+		for (; nsect > 0; nsect--, block++, buf += tr->blksize) {
+			if (tr->readsect(dev, block, buf)) {
+				kunmap(bio_page(req->bio));
+				return BLK_STS_IOERR;
+			}
+		}
+		kunmap(bio_page(req->bio));
+
+		rq_for_each_segment(bvec, req, iter)
+			flush_dcache_page(bvec.bv_page);
+		return BLK_STS_OK;
+	case REQ_OP_WRITE:
+		if (!tr->writesect)
+			return BLK_STS_IOERR;
+
+		rq_for_each_segment(bvec, req, iter)
+			flush_dcache_page(bvec.bv_page);
+
+		buf = kmap(bio_page(req->bio)) + bio_offset(req->bio);
+		for (; nsect > 0; nsect--, block++, buf += tr->blksize) {
+			if (tr->writesect(dev, block, buf)) {
+				kunmap(bio_page(req->bio));
+				return BLK_STS_IOERR;
+			}
+		}
+		kunmap(bio_page(req->bio));
+		return BLK_STS_OK;
+	default:
+		return BLK_STS_IOERR;
+	}
+}
+
+int mtd_blktrans_cease_background(struct mtd_blktrans_dev *dev)
+{
+	return dev->bg_stop;
+}
+EXPORT_SYMBOL_GPL(mtd_blktrans_cease_background);
+
+static struct request *mtd_next_request(struct mtd_blktrans_dev *dev)
+{
+	struct request *rq;
+
+	rq = list_first_entry_or_null(&dev->rq_list, struct request, queuelist);
+	if (rq) {
+		list_del_init(&rq->queuelist);
+		blk_mq_start_request(rq);
+		return rq;
+	}
+
+	return NULL;
+}
+
+static void mtd_blktrans_work(struct mtd_blktrans_dev *dev)
+	__releases(&dev->queue_lock)
+	__acquires(&dev->queue_lock)
+{
+	struct mtd_blktrans_ops *tr = dev->tr;
+	struct request *req = NULL;
+	int background_done = 0;
+
+	while (1) {
+		blk_status_t res;
+
+		dev->bg_stop = false;
+		if (!req && !(req = mtd_next_request(dev))) {
+			if (tr->background && !background_done) {
+				spin_unlock_irq(&dev->queue_lock);
+				mutex_lock(&dev->lock);
+				tr->background(dev);
+				mutex_unlock(&dev->lock);
+				spin_lock_irq(&dev->queue_lock);
+				/*
+				 * Do background processing just once per idle
+				 * period.
+				 */
+				background_done = !dev->bg_stop;
+				continue;
+			}
+			break;
+		}
+
+		spin_unlock_irq(&dev->queue_lock);
+
+		mutex_lock(&dev->lock);
+		res = do_blktrans_request(dev->tr, dev, req);
+		mutex_unlock(&dev->lock);
+
+		if (!blk_update_request(req, res, blk_rq_cur_bytes(req))) {
+			__blk_mq_end_request(req, res);
+			req = NULL;
+		}
+
+		background_done = 0;
+		cond_resched();
+		spin_lock_irq(&dev->queue_lock);
+	}
+}
+
+static blk_status_t mtd_queue_rq(struct blk_mq_hw_ctx *hctx,
+				 const struct blk_mq_queue_data *bd)
+{
+	struct mtd_blktrans_dev *dev;
+
+	dev = hctx->queue->queuedata;
+	if (!dev) {
+		blk_mq_start_request(bd->rq);
+		return BLK_STS_IOERR;
+	}
+
+	spin_lock_irq(&dev->queue_lock);
+	list_add_tail(&bd->rq->queuelist, &dev->rq_list);
+	mtd_blktrans_work(dev);
+	spin_unlock_irq(&dev->queue_lock);
+
+	return BLK_STS_OK;
+}
+
+static int blktrans_open(struct gendisk *disk, blk_mode_t mode)
+{
+	struct mtd_blktrans_dev *dev = disk->private_data;
+	int ret = 0;
+
+	kref_get(&dev->ref);
+
+	mutex_lock(&dev->lock);
+
+	if (dev->open)
+		goto unlock;
+
+	__module_get(dev->tr->owner);
+
+	if (!dev->mtd)
+		goto unlock;
+
+	if (dev->tr->open) {
+		ret = dev->tr->open(dev);
+		if (ret)
+			goto error_put;
+	}
+
+	ret = __get_mtd_device(dev->mtd);
+	if (ret)
+		goto error_release;
+	dev->writable = mode & BLK_OPEN_WRITE;
+
+unlock:
+	dev->open++;
+	mutex_unlock(&dev->lock);
+	return ret;
+
+error_release:
+	if (dev->tr->release)
+		dev->tr->release(dev);
+error_put:
+	module_put(dev->tr->owner);
+	mutex_unlock(&dev->lock);
+	blktrans_dev_put(dev);
+	return ret;
+}
+
+static void blktrans_release(struct gendisk *disk)
+{
+	struct mtd_blktrans_dev *dev = disk->private_data;
+
+	mutex_lock(&dev->lock);
+
+	if (--dev->open)
+		goto unlock;
+
+	module_put(dev->tr->owner);
+
+	if (dev->mtd) {
+		if (dev->tr->release)
+			dev->tr->release(dev);
+		__put_mtd_device(dev->mtd);
+	}
+unlock:
+	mutex_unlock(&dev->lock);
+	blktrans_dev_put(dev);
+}
+
+static int blktrans_getgeo(struct gendisk *disk, struct hd_geometry *geo)
+{
+	struct mtd_blktrans_dev *dev = disk->private_data;
+	int ret = -ENXIO;
+
+	mutex_lock(&dev->lock);
+
+	if (!dev->mtd)
+		goto unlock;
+
+	ret = dev->tr->getgeo ? dev->tr->getgeo(dev, geo) : -ENOTTY;
+unlock:
+	mutex_unlock(&dev->lock);
+	return ret;
+}
+
+static const struct block_device_operations mtd_block_ops = {
+	.owner		= THIS_MODULE,
+	.open		= blktrans_open,
+	.release	= blktrans_release,
+	.getgeo		= blktrans_getgeo,
+};
+
+static const struct blk_mq_ops mtd_mq_ops = {
+	.queue_rq	= mtd_queue_rq,
+};
+
+int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
+{
+	struct mtd_blktrans_ops *tr = new->tr;
+	struct mtd_blktrans_dev *d;
+	struct queue_limits lim = { };
+	int last_devnum = -1;
+	struct gendisk *gd;
+	int ret;
+
+	lockdep_assert_held(&mtd_table_mutex);
+
+	list_for_each_entry(d, &tr->devs, list) {
+		if (new->devnum == -1) {
+			/* Use first free number */
+			if (d->devnum != last_devnum+1) {
+				/* Found a free devnum. Plug it in here */
+				new->devnum = last_devnum+1;
+				list_add_tail(&new->list, &d->list);
+				goto added;
+			}
+		} else if (d->devnum == new->devnum) {
+			/* Required number taken */
+			return -EBUSY;
+		} else if (d->devnum > new->devnum) {
+			/* Required number was free */
+			list_add_tail(&new->list, &d->list);
+			goto added;
+		}
+		last_devnum = d->devnum;
+	}
+
+	ret = -EBUSY;
+	if (new->devnum == -1)
+		new->devnum = last_devnum+1;
+
+	/* Check that the device and any partitions will get valid
+	 * minor numbers and that the disk naming code below can cope
+	 * with this number. */
+	if (new->devnum > (MINORMASK >> tr->part_bits) ||
+	    (tr->part_bits && new->devnum >= 27 * 26))
+		return ret;
+
+	list_add_tail(&new->list, &tr->devs);
+ added:
+
+	mutex_init(&new->lock);
+	kref_init(&new->ref);
+	if (!tr->writesect)
+		new->readonly = 1;
+
+	ret = -ENOMEM;
+	new->tag_set = kzalloc_obj(*new->tag_set);
+	if (!new->tag_set)
+		goto out_list_del;
+
+	ret = blk_mq_alloc_sq_tag_set(new->tag_set, &mtd_mq_ops, 2,
+			BLK_MQ_F_BLOCKING);
+	if (ret)
+		goto out_kfree_tag_set;
+	
+	lim.logical_block_size = tr->blksize;
+	if (tr->discard)
+		lim.max_hw_discard_sectors = UINT_MAX;
+	if (tr->flush)
+		lim.features |= BLK_FEAT_WRITE_CACHE;
+
+	/* Create gendisk */
+	gd = blk_mq_alloc_disk(new->tag_set, &lim, new);
+	if (IS_ERR(gd)) {
+		ret = PTR_ERR(gd);
+		goto out_free_tag_set;
+	}
+
+	new->disk = gd;
+	new->rq = new->disk->queue;
+	gd->private_data = new;
+	gd->major = tr->major;
+	gd->first_minor = (new->devnum) << tr->part_bits;
+	gd->minors = 1 << tr->part_bits;
+	gd->fops = &mtd_block_ops;
+
+	if (tr->part_bits) {
+		if (new->devnum < 26)
+			snprintf(gd->disk_name, sizeof(gd->disk_name),
+				 "%s%c", tr->name, 'a' + new->devnum);
+		else
+			snprintf(gd->disk_name, sizeof(gd->disk_name),
+				 "%s%c%c", tr->name,
+				 'a' - 1 + new->devnum / 26,
+				 'a' + new->devnum % 26);
+	} else {
+		snprintf(gd->disk_name, sizeof(gd->disk_name),
+			 "%s%d", tr->name, new->devnum);
+		gd->flags |= GENHD_FL_NO_PART;
+	}
+
+	set_capacity(gd, ((u64)new->size * tr->blksize) >> 9);
+
+	/* Create the request queue */
+	spin_lock_init(&new->queue_lock);
+	INIT_LIST_HEAD(&new->rq_list);
+	gd->queue = new->rq;
+
+	if (new->readonly)
+		set_disk_ro(gd, 1);
+
+	ret = device_add_disk(&new->mtd->dev, gd, NULL);
+	if (ret)
+		goto out_cleanup_disk;
+
+	if (new->disk_attributes) {
+		ret = sysfs_create_group(&disk_to_dev(gd)->kobj,
+					new->disk_attributes);
+		WARN_ON(ret);
+	}
+	return 0;
+
+out_cleanup_disk:
+	put_disk(new->disk);
+out_free_tag_set:
+	blk_mq_free_tag_set(new->tag_set);
+out_kfree_tag_set:
+	kfree(new->tag_set);
+out_list_del:
+	list_del(&new->list);
+	return ret;
+}
+
+int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
+{
+	unsigned long flags;
+	unsigned int memflags;
+
+	lockdep_assert_held(&mtd_table_mutex);
+
+	if (old->disk_attributes)
+		sysfs_remove_group(&disk_to_dev(old->disk)->kobj,
+						old->disk_attributes);
+
+	/* Stop new requests to arrive */
+	del_gendisk(old->disk);
+
+	/* Kill current requests */
+	spin_lock_irqsave(&old->queue_lock, flags);
+	old->rq->queuedata = NULL;
+	spin_unlock_irqrestore(&old->queue_lock, flags);
+
+	/* freeze+quiesce queue to ensure all requests are flushed */
+	memflags = blk_mq_freeze_queue(old->rq);
+	blk_mq_quiesce_queue(old->rq);
+	blk_mq_unquiesce_queue(old->rq);
+	blk_mq_unfreeze_queue(old->rq, memflags);
+
+	/* If the device is currently open, tell trans driver to close it,
+		then put mtd device, and don't touch it again */
+	mutex_lock(&old->lock);
+	if (old->open) {
+		if (old->tr->release)
+			old->tr->release(old);
+		__put_mtd_device(old->mtd);
+	}
+
+	old->mtd = NULL;
+
+	mutex_unlock(&old->lock);
+	blktrans_dev_put(old);
+	return 0;
+}
+
+static void blktrans_notify_remove(struct mtd_info *mtd)
+{
+	struct mtd_blktrans_ops *tr;
+	struct mtd_blktrans_dev *dev, *next;
+
+	list_for_each_entry(tr, &blktrans_majors, list)
+		list_for_each_entry_safe(dev, next, &tr->devs, list)
+			if (dev->mtd == mtd)
+				tr->remove_dev(dev);
+}
+
+static void blktrans_notify_add(struct mtd_info *mtd)
+{
+	struct mtd_blktrans_ops *tr;
+
+	if (mtd->type == MTD_ABSENT || mtd->type == MTD_UBIVOLUME)
+		return;
+
+	list_for_each_entry(tr, &blktrans_majors, list)
+		tr->add_mtd(tr, mtd);
+}
+
+static struct mtd_notifier blktrans_notifier = {
+	.add = blktrans_notify_add,
+	.remove = blktrans_notify_remove,
+};
+
+int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
+{
+	struct mtd_info *mtd;
+	int ret;
+
+	/* Register the notifier if/when the first device type is
+	   registered, to prevent the link/init ordering from fucking
+	   us over. */
+	if (!blktrans_notifier.list.next)
+		register_mtd_user(&blktrans_notifier);
+
+	ret = register_blkdev(tr->major, tr->name);
+	if (ret < 0) {
+		printk(KERN_WARNING "Unable to register %s block device on major %d: %d\n",
+		       tr->name, tr->major, ret);
+		return ret;
+	}
+
+	if (ret)
+		tr->major = ret;
+
+	tr->blkshift = ffs(tr->blksize) - 1;
+
+	INIT_LIST_HEAD(&tr->devs);
+
+	mutex_lock(&mtd_table_mutex);
+	list_add(&tr->list, &blktrans_majors);
+	mtd_for_each_device(mtd)
+		if (mtd->type != MTD_ABSENT && mtd->type != MTD_UBIVOLUME)
+			tr->add_mtd(tr, mtd);
+	mutex_unlock(&mtd_table_mutex);
+	return 0;
+}
+
+int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
+{
+	struct mtd_blktrans_dev *dev, *next;
+
+	mutex_lock(&mtd_table_mutex);
+
+	/* Remove it from the list of active majors */
+	list_del(&tr->list);
+
+	list_for_each_entry_safe(dev, next, &tr->devs, list)
+		tr->remove_dev(dev);
+
+	mutex_unlock(&mtd_table_mutex);
+	unregister_blkdev(tr->major, tr->name);
+
+	BUG_ON(!list_empty(&tr->devs));
+	return 0;
+}
+
+static void __exit mtd_blktrans_exit(void)
+{
+	/* No race here -- if someone's currently in register_mtd_blktrans
+	   we're screwed anyway. */
+	if (blktrans_notifier.list.next)
+		unregister_mtd_user(&blktrans_notifier);
+}
+
+module_exit(mtd_blktrans_exit);
+
+EXPORT_SYMBOL_GPL(register_mtd_blktrans);
+EXPORT_SYMBOL_GPL(deregister_mtd_blktrans);
+EXPORT_SYMBOL_GPL(add_mtd_blktrans_dev);
+EXPORT_SYMBOL_GPL(del_mtd_blktrans_dev);
+
+MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Common interface to block layer for MTD 'translation layers'");