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, 516 insertions, 0 deletions

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
new file mode 100644
index 000000000..750865fd3
--- /dev/null
+++ b/drivers/md/dm-stripe.c
@@ -0,0 +1,516 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include <linux/device-mapper.h>
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/dax.h>
+#include <linux/slab.h>
+#include <linux/log2.h>
+
+static struct workqueue_struct *dm_stripe_wq;
+
+#define DM_MSG_PREFIX "striped"
+#define DM_IO_ERROR_THRESHOLD 15
+
+struct stripe {
+	struct dm_dev *dev;
+	sector_t physical_start;
+
+	atomic_t error_count;
+};
+
+struct stripe_c {
+	uint32_t stripes;
+	int stripes_shift;
+
+	/* The size of this target / num. stripes */
+	sector_t stripe_width;
+
+	uint32_t chunk_size;
+	int chunk_size_shift;
+
+	/* Needed for handling events */
+	struct dm_target *ti;
+
+	/* Work struct used for triggering events*/
+	struct work_struct trigger_event;
+
+	struct stripe stripe[] __counted_by(stripes);
+};
+
+/*
+ * An event is triggered whenever a drive
+ * drops out of a stripe volume.
+ */
+static void trigger_event(struct work_struct *work)
+{
+	struct stripe_c *sc = container_of(work, struct stripe_c,
+					   trigger_event);
+	dm_table_event(sc->ti->table);
+}
+
+/*
+ * Parse a single <dev> <sector> pair
+ */
+static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
+		      unsigned int stripe, char **argv)
+{
+	unsigned long long start;
+	char dummy;
+	int ret;
+
+	if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
+		return -EINVAL;
+
+	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
+			    &sc->stripe[stripe].dev);
+	if (ret)
+		return ret;
+
+	sc->stripe[stripe].physical_start = start;
+
+	return 0;
+}
+
+/*
+ * Construct a striped mapping.
+ * <number of stripes> <chunk size> [<dev_path> <offset>]+
+ */
+static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	struct stripe_c *sc;
+	sector_t width, tmp_len;
+	uint32_t stripes;
+	uint32_t chunk_size;
+	int r;
+	unsigned int i;
+
+	if (argc < 2) {
+		ti->error = "Not enough arguments";
+		return -EINVAL;
+	}
+
+	if (kstrtouint(argv[0], 10, &stripes) || !stripes) {
+		ti->error = "Invalid stripe count";
+		return -EINVAL;
+	}
+
+	if (kstrtouint(argv[1], 10, &chunk_size) || !chunk_size) {
+		ti->error = "Invalid chunk_size";
+		return -EINVAL;
+	}
+
+	width = ti->len;
+	if (sector_div(width, stripes)) {
+		ti->error = "Target length not divisible by number of stripes";
+		return -EINVAL;
+	}
+
+	tmp_len = width;
+	if (sector_div(tmp_len, chunk_size)) {
+		ti->error = "Target length not divisible by chunk size";
+		return -EINVAL;
+	}
+
+	/*
+	 * Do we have enough arguments for that many stripes ?
+	 */
+	if (argc != (2 + 2 * stripes)) {
+		ti->error = "Not enough destinations specified";
+		return -EINVAL;
+	}
+
+	sc = kmalloc_flex(*sc, stripe, stripes);
+	if (!sc) {
+		ti->error = "Memory allocation for striped context failed";
+		return -ENOMEM;
+	}
+
+	INIT_WORK(&sc->trigger_event, trigger_event);
+
+	/* Set pointer to dm target; used in trigger_event */
+	sc->ti = ti;
+	sc->stripes = stripes;
+	sc->stripe_width = width;
+
+	if (stripes & (stripes - 1))
+		sc->stripes_shift = -1;
+	else
+		sc->stripes_shift = __ffs(stripes);
+
+	r = dm_set_target_max_io_len(ti, chunk_size);
+	if (r) {
+		kfree(sc);
+		return r;
+	}
+
+	ti->num_flush_bios = stripes;
+	ti->num_discard_bios = stripes;
+	ti->num_secure_erase_bios = stripes;
+	ti->num_write_zeroes_bios = stripes;
+	ti->flush_bypasses_map = true;
+
+	sc->chunk_size = chunk_size;
+	if (chunk_size & (chunk_size - 1))
+		sc->chunk_size_shift = -1;
+	else
+		sc->chunk_size_shift = __ffs(chunk_size);
+
+	/*
+	 * Get the stripe destinations.
+	 */
+	for (i = 0; i < stripes; i++) {
+		argv += 2;
+
+		r = get_stripe(ti, sc, i, argv);
+		if (r < 0) {
+			ti->error = "Couldn't parse stripe destination";
+			while (i--)
+				dm_put_device(ti, sc->stripe[i].dev);
+			kfree(sc);
+			return r;
+		}
+		atomic_set(&(sc->stripe[i].error_count), 0);
+	}
+
+	ti->private = sc;
+
+	return 0;
+}
+
+static void stripe_dtr(struct dm_target *ti)
+{
+	unsigned int i;
+	struct stripe_c *sc = ti->private;
+
+	for (i = 0; i < sc->stripes; i++)
+		dm_put_device(ti, sc->stripe[i].dev);
+
+	flush_work(&sc->trigger_event);
+	kfree(sc);
+}
+
+static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
+			      uint32_t *stripe, sector_t *result)
+{
+	sector_t chunk = dm_target_offset(sc->ti, sector);
+	sector_t chunk_offset;
+
+	if (sc->chunk_size_shift < 0)
+		chunk_offset = sector_div(chunk, sc->chunk_size);
+	else {
+		chunk_offset = chunk & (sc->chunk_size - 1);
+		chunk >>= sc->chunk_size_shift;
+	}
+
+	if (sc->stripes_shift < 0)
+		*stripe = sector_div(chunk, sc->stripes);
+	else {
+		*stripe = chunk & (sc->stripes - 1);
+		chunk >>= sc->stripes_shift;
+	}
+
+	if (sc->chunk_size_shift < 0)
+		chunk *= sc->chunk_size;
+	else
+		chunk <<= sc->chunk_size_shift;
+
+	*result = chunk + chunk_offset;
+}
+
+static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
+				    uint32_t target_stripe, sector_t *result)
+{
+	uint32_t stripe;
+
+	stripe_map_sector(sc, sector, &stripe, result);
+	if (stripe == target_stripe)
+		return;
+
+	/* round down */
+	sector = *result;
+	if (sc->chunk_size_shift < 0)
+		*result -= sector_div(sector, sc->chunk_size);
+	else
+		*result = sector & ~(sector_t)(sc->chunk_size - 1);
+
+	if (target_stripe < stripe)
+		*result += sc->chunk_size;		/* next chunk */
+}
+
+static int stripe_map_range(struct stripe_c *sc, struct bio *bio,
+			    uint32_t target_stripe)
+{
+	sector_t begin, end;
+
+	stripe_map_range_sector(sc, bio->bi_iter.bi_sector,
+				target_stripe, &begin);
+	stripe_map_range_sector(sc, bio_end_sector(bio),
+				target_stripe, &end);
+	if (begin < end) {
+		bio_set_dev(bio, sc->stripe[target_stripe].dev->bdev);
+		bio->bi_iter.bi_sector = begin +
+			sc->stripe[target_stripe].physical_start;
+		bio->bi_iter.bi_size = to_bytes(end - begin);
+		return DM_MAPIO_REMAPPED;
+	}
+
+	/* The range doesn't map to the target stripe */
+	bio_endio(bio);
+	return DM_MAPIO_SUBMITTED;
+}
+
+int stripe_map(struct dm_target *ti, struct bio *bio)
+{
+	struct stripe_c *sc = ti->private;
+	uint32_t stripe;
+	unsigned int target_bio_nr;
+
+	if (bio->bi_opf & REQ_PREFLUSH) {
+		target_bio_nr = dm_bio_get_target_bio_nr(bio);
+		BUG_ON(target_bio_nr >= sc->stripes);
+		bio_set_dev(bio, sc->stripe[target_bio_nr].dev->bdev);
+		return DM_MAPIO_REMAPPED;
+	}
+	if (unlikely(bio_op(bio) == REQ_OP_DISCARD) ||
+	    unlikely(bio_op(bio) == REQ_OP_SECURE_ERASE) ||
+	    unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES)) {
+		target_bio_nr = dm_bio_get_target_bio_nr(bio);
+		BUG_ON(target_bio_nr >= sc->stripes);
+		return stripe_map_range(sc, bio, target_bio_nr);
+	}
+
+	stripe_map_sector(sc, bio->bi_iter.bi_sector,
+			  &stripe, &bio->bi_iter.bi_sector);
+
+	bio->bi_iter.bi_sector += sc->stripe[stripe].physical_start;
+	bio_set_dev(bio, sc->stripe[stripe].dev->bdev);
+
+	return DM_MAPIO_REMAPPED;
+}
+
+#if IS_ENABLED(CONFIG_FS_DAX)
+static struct dax_device *stripe_dax_pgoff(struct dm_target *ti, pgoff_t *pgoff)
+{
+	struct stripe_c *sc = ti->private;
+	struct block_device *bdev;
+	sector_t dev_sector;
+	uint32_t stripe;
+
+	stripe_map_sector(sc, *pgoff * PAGE_SECTORS, &stripe, &dev_sector);
+	dev_sector += sc->stripe[stripe].physical_start;
+	bdev = sc->stripe[stripe].dev->bdev;
+
+	*pgoff = (get_start_sect(bdev) + dev_sector) >> PAGE_SECTORS_SHIFT;
+	return sc->stripe[stripe].dev->dax_dev;
+}
+
+static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+		long nr_pages, enum dax_access_mode mode, void **kaddr,
+		unsigned long *pfn)
+{
+	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);
+
+	return dax_direct_access(dax_dev, pgoff, nr_pages, mode, kaddr, pfn);
+}
+
+static int stripe_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
+				      size_t nr_pages)
+{
+	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);
+
+	return dax_zero_page_range(dax_dev, pgoff, nr_pages);
+}
+
+static size_t stripe_dax_recovery_write(struct dm_target *ti, pgoff_t pgoff,
+		void *addr, size_t bytes, struct iov_iter *i)
+{
+	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);
+
+	return dax_recovery_write(dax_dev, pgoff, addr, bytes, i);
+}
+
+#else
+#define stripe_dax_direct_access NULL
+#define stripe_dax_zero_page_range NULL
+#define stripe_dax_recovery_write NULL
+#endif
+
+/*
+ * Stripe status:
+ *
+ * INFO
+ * #stripes [stripe_name <stripe_name>] [group word count]
+ * [error count 'A|D' <error count 'A|D'>]
+ *
+ * TABLE
+ * #stripes [stripe chunk size]
+ * [stripe_name physical_start <stripe_name physical_start>]
+ *
+ */
+
+static void stripe_status(struct dm_target *ti, status_type_t type,
+			  unsigned int status_flags, char *result, unsigned int maxlen)
+{
+	struct stripe_c *sc = ti->private;
+	unsigned int sz = 0;
+	unsigned int i;
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		DMEMIT("%d ", sc->stripes);
+		for (i = 0; i < sc->stripes; i++)
+			DMEMIT("%s ", sc->stripe[i].dev->name);
+
+		DMEMIT("1 ");
+		for (i = 0; i < sc->stripes; i++)
+			DMEMIT("%c", atomic_read(&(sc->stripe[i].error_count)) ?  'D' : 'A');
+		break;
+
+	case STATUSTYPE_TABLE:
+		DMEMIT("%d %llu", sc->stripes,
+			(unsigned long long)sc->chunk_size);
+		for (i = 0; i < sc->stripes; i++)
+			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
+			    (unsigned long long)sc->stripe[i].physical_start);
+		break;
+
+	case STATUSTYPE_IMA:
+		DMEMIT_TARGET_NAME_VERSION(ti->type);
+		DMEMIT(",stripes=%d,chunk_size=%llu", sc->stripes,
+		       (unsigned long long)sc->chunk_size);
+
+		for (i = 0; i < sc->stripes; i++) {
+			DMEMIT(",stripe_%d_device_name=%s", i, sc->stripe[i].dev->name);
+			DMEMIT(",stripe_%d_physical_start=%llu", i,
+			       (unsigned long long)sc->stripe[i].physical_start);
+			DMEMIT(",stripe_%d_status=%c", i,
+			       atomic_read(&(sc->stripe[i].error_count)) ? 'D' : 'A');
+		}
+		DMEMIT(";");
+		break;
+	}
+}
+
+static int stripe_end_io(struct dm_target *ti, struct bio *bio,
+		blk_status_t *error)
+{
+	unsigned int i;
+	char major_minor[22];
+	struct stripe_c *sc = ti->private;
+
+	if (!*error)
+		return DM_ENDIO_DONE; /* I/O complete */
+
+	if (bio->bi_opf & REQ_RAHEAD)
+		return DM_ENDIO_DONE;
+
+	if (*error == BLK_STS_NOTSUPP)
+		return DM_ENDIO_DONE;
+
+	format_dev_t(major_minor, bio_dev(bio));
+
+	/*
+	 * Test to see which stripe drive triggered the event
+	 * and increment error count for all stripes on that device.
+	 * If the error count for a given device exceeds the threshold
+	 * value we will no longer trigger any further events.
+	 */
+	for (i = 0; i < sc->stripes; i++)
+		if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
+			atomic_inc(&(sc->stripe[i].error_count));
+			if (atomic_read(&(sc->stripe[i].error_count)) <
+			    DM_IO_ERROR_THRESHOLD)
+				queue_work(dm_stripe_wq, &sc->trigger_event);
+		}
+
+	return DM_ENDIO_DONE;
+}
+
+static int stripe_iterate_devices(struct dm_target *ti,
+				  iterate_devices_callout_fn fn, void *data)
+{
+	struct stripe_c *sc = ti->private;
+	int ret = 0;
+	unsigned int i = 0;
+
+	do {
+		ret = fn(ti, sc->stripe[i].dev,
+			 sc->stripe[i].physical_start,
+			 sc->stripe_width, data);
+	} while (!ret && ++i < sc->stripes);
+
+	return ret;
+}
+
+static void stripe_io_hints(struct dm_target *ti,
+			    struct queue_limits *limits)
+{
+	struct stripe_c *sc = ti->private;
+	unsigned int io_min, io_opt, max_hw_discard_sectors = limits->max_hw_discard_sectors;
+
+	limits->chunk_sectors = sc->chunk_size;
+
+	if (!check_shl_overflow(sc->chunk_size, SECTOR_SHIFT, &io_min) &&
+	    !check_mul_overflow(io_min, sc->stripes, &io_opt)) {
+		limits->io_min = io_min;
+		limits->io_opt = io_opt;
+	}
+	if (max_hw_discard_sectors >= sc->chunk_size) {
+		if (!check_mul_overflow(max_hw_discard_sectors, sc->stripes, &max_hw_discard_sectors)) {
+			max_hw_discard_sectors = rounddown(max_hw_discard_sectors,
+					sc->chunk_size * sc->stripes);
+			limits->max_hw_discard_sectors = max_hw_discard_sectors;
+		} else
+			limits->max_hw_discard_sectors = UINT_MAX >> SECTOR_SHIFT;
+	}
+}
+
+static struct target_type stripe_target = {
+	.name   = "striped",
+	.version = {1, 7, 0},
+	.features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_NOWAIT |
+		    DM_TARGET_ATOMIC_WRITES | DM_TARGET_PASSES_CRYPTO,
+	.module = THIS_MODULE,
+	.ctr    = stripe_ctr,
+	.dtr    = stripe_dtr,
+	.map    = stripe_map,
+	.end_io = stripe_end_io,
+	.status = stripe_status,
+	.iterate_devices = stripe_iterate_devices,
+	.io_hints = stripe_io_hints,
+	.direct_access = stripe_dax_direct_access,
+	.dax_zero_page_range = stripe_dax_zero_page_range,
+	.dax_recovery_write = stripe_dax_recovery_write,
+};
+
+int __init dm_stripe_init(void)
+{
+	int r;
+
+	dm_stripe_wq = alloc_workqueue("dm_stripe_wq", WQ_PERCPU, 0);
+	if (!dm_stripe_wq)
+		return -ENOMEM;
+	r = dm_register_target(&stripe_target);
+	if (r < 0) {
+		destroy_workqueue(dm_stripe_wq);
+		DMWARN("target registration failed");
+	}
+
+	return r;
+}
+
+void dm_stripe_exit(void)
+{
+	dm_unregister_target(&stripe_target);
+	destroy_workqueue(dm_stripe_wq);
+}