From: Mikulas Patocka <[email-masked]>

Avoid returning a truncated table or status string instead of setting
the DM_BUFFER_FULL_FLAG when the last target of a table fills the
buffer.

When processing a table or status request, the function retrieve_status
calls ti->type->status. If ti->type->status returns non-zero,
retrieve_status assumes that the buffer overflowed and sets
DM_BUFFER_FULL_FLAG.

However, targets don't return non-zero values from their status method
on overflow. Most targets returns always zero.

If a buffer overflow happens in a target that is not the last in the
table, it gets noticed during the next iteration of the loop in
retrieve_status; but if a buffer overflow happens in the last target, it
goes unnoticed and erroneously truncated data is returned.

In the current code, the targets behave in the following way:
* dm-crypt returns -ENOMEM if there is not enough space to store the
  key, but it returns 0 on all other overflows.
* dm-thin returns errors from the status method if a disk error happened.
  This is incorrect because retrieve_status doesn't check the error
  code, it assumes that all non-zero values mean buffer overflow.
* all the other targets always return 0.

This patch changes the ti->type->status function to return void (because
most targets don't use the return code). Overflow is detected in
retrieve_status: if the status method fills up the remaining space
completely, it is assumed that buffer overflow happened.

Cc: [email-masked]
Signed-off-by: Mikulas Patocka <[email-masked]>
Signed-off-by: Alasdair G Kergon <[email-masked]>

---
drivers/md/dm-crypt.c         |   32 ++++-----------------
 drivers/md/dm-crypt.c         |   39 ++++---------------
 drivers/md/dm-delay.c         |    8 +---
 drivers/md/dm-flakey.c        |    7 +--
 drivers/md/dm-ioctl.c         |   14 ++++---
 drivers/md/dm-linear.c        |    7 +--
 drivers/md/dm-mpath.c         |    8 +---
 drivers/md/dm-raid.c          |    8 +---
 drivers/md/dm-raid1.c         |    8 +---
 drivers/md/dm-snap.c          |   16 +++-----
 drivers/md/dm-stripe.c        |    7 +--
 drivers/md/dm-thin.c          |   82 +++++++++++++++++++++++++-----------------
 drivers/md/dm-verity.c        |    8 +---
 include/linux/device-mapper.h |    4 +-
 13 files changed, 100 insertions(+), 116 deletions(-)

Index: linux/drivers/md/dm-crypt.c
===================================================================
--- linux.orig/drivers/md/dm-crypt.c
+++ linux/drivers/md/dm-crypt.c
@@ -1234,20 +1234,6 @@ static int crypt_decode_key(u8 *key, cha
 	return 0;
 }
 
-/*
- * Encode key into its hex representation
- */
-static void crypt_encode_key(char *hex, u8 *key, unsigned int size)
-{
-	unsigned int i;
-
-	for (i = 0; i < size; i++) {
-		sprintf(hex, "%02x", *key);
-		hex += 2;
-		key++;
-	}
-}
-
 static void crypt_free_tfms(struct crypt_config *cc)
 {
 	unsigned i;
@@ -1717,11 +1703,11 @@ static int crypt_map(struct dm_target *t
 	return DM_MAPIO_SUBMITTED;
 }
 
-static int crypt_status(struct dm_target *ti, status_type_t type,
-			unsigned status_flags, char *result, unsigned maxlen)
+static void crypt_status(struct dm_target *ti, status_type_t type,
+			 unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct crypt_config *cc = ti->private;
-	unsigned int sz = 0;
+	unsigned i, sz = 0;
 
 	switch (type) {
 	case STATUSTYPE_INFO:
@@ -1731,17 +1717,11 @@ static int crypt_status(struct dm_target
 	case STATUSTYPE_TABLE:
 		DMEMIT("%s ", cc->cipher_string);
 
-		if (cc->key_size > 0) {
-			if ((maxlen - sz) < ((cc->key_size << 1) + 1))
-				return -ENOMEM;
-
-			crypt_encode_key(result + sz, cc->key, cc->key_size);
-			sz += cc->key_size << 1;
-		} else {
-			if (sz >= maxlen)
-				return -ENOMEM;
-			result[sz++] = '-';
-		}
+		if (cc->key_size > 0)
+			for (i = 0; i < cc->key_size; i++)
+				DMEMIT("%02x", cc->key[i]);
+		else
+			DMEMIT("-");
 
 		DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset,
 				cc->dev->name, (unsigned long long)cc->start);
@@ -1751,7 +1731,6 @@ static int crypt_status(struct dm_target
 
 		break;
 	}
-	return 0;
 }
 
 static void crypt_postsuspend(struct dm_target *ti)
@@ -1845,7 +1824,7 @@ static int crypt_iterate_devices(struct 
 
 static struct target_type crypt_target = {
 	.name   = "crypt",
-	.version = {1, 12, 0},
+	.version = {1, 12, 1},
 	.module = THIS_MODULE,
 	.ctr    = crypt_ctr,
 	.dtr    = crypt_dtr,
Index: linux/drivers/md/dm-delay.c
===================================================================
--- linux.orig/drivers/md/dm-delay.c
+++ linux/drivers/md/dm-delay.c
@@ -293,8 +293,8 @@ static int delay_map(struct dm_target *t
 	return delay_bio(dc, dc->read_delay, bio);
 }
 
-static int delay_status(struct dm_target *ti, status_type_t type,
-			unsigned status_flags, char *result, unsigned maxlen)
+static void delay_status(struct dm_target *ti, status_type_t type,
+			 unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct delay_c *dc = ti->private;
 	int sz = 0;
@@ -314,8 +314,6 @@ static int delay_status(struct dm_target
 			       dc->write_delay);
 		break;
 	}
-
-	return 0;
 }
 
 static int delay_iterate_devices(struct dm_target *ti,
@@ -337,7 +335,7 @@ out:
 
 static struct target_type delay_target = {
 	.name	     = "delay",
-	.version     = {1, 2, 0},
+	.version     = {1, 2, 1},
 	.module      = THIS_MODULE,
 	.ctr	     = delay_ctr,
 	.dtr	     = delay_dtr,
Index: linux/drivers/md/dm-flakey.c
===================================================================
--- linux.orig/drivers/md/dm-flakey.c
+++ linux/drivers/md/dm-flakey.c
@@ -337,8 +337,8 @@ static int flakey_end_io(struct dm_targe
 	return error;
 }
 
-static int flakey_status(struct dm_target *ti, status_type_t type,
-			 unsigned status_flags, char *result, unsigned maxlen)
+static void flakey_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
 {
 	unsigned sz = 0;
 	struct flakey_c *fc = ti->private;
@@ -368,7 +368,6 @@ static int flakey_status(struct dm_targe
 
 		break;
 	}
-	return 0;
 }
 
 static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
@@ -411,7 +410,7 @@ static int flakey_iterate_devices(struct
 
 static struct target_type flakey_target = {
 	.name   = "flakey",
-	.version = {1, 3, 0},
+	.version = {1, 3, 1},
 	.module = THIS_MODULE,
 	.ctr    = flakey_ctr,
 	.dtr    = flakey_dtr,
Index: linux/drivers/md/dm-ioctl.c
===================================================================
--- linux.orig/drivers/md/dm-ioctl.c
+++ linux/drivers/md/dm-ioctl.c
@@ -1067,6 +1067,7 @@ static void retrieve_status(struct dm_ta
 	num_targets = dm_table_get_num_targets(table);
 	for (i = 0; i < num_targets; i++) {
 		struct dm_target *ti = dm_table_get_target(table, i);
+		size_t l;
 
 		remaining = len - (outptr - outbuf);
 		if (remaining <= sizeof(struct dm_target_spec)) {
@@ -1093,14 +1094,17 @@ static void retrieve_status(struct dm_ta
 		if (ti->type->status) {
 			if (param->flags & DM_NOFLUSH_FLAG)
 				status_flags |= DM_STATUS_NOFLUSH_FLAG;
-			if (ti->type->status(ti, type, status_flags, outptr, remaining)) {
-				param->flags |= DM_BUFFER_FULL_FLAG;
-				break;
-			}
+			ti->type->status(ti, type, status_flags, outptr, remaining);
 		} else
 			outptr[0] = '\0';
 
-		outptr += strlen(outptr) + 1;
+		l = strlen(outptr) + 1;
+		if (l == remaining) {
+			param->flags |= DM_BUFFER_FULL_FLAG;
+			break;
+		}
+
+		outptr += l;
 		used = param->data_start + (outptr - outbuf);
 
 		outptr = align_ptr(outptr);
Index: linux/drivers/md/dm-linear.c
===================================================================
--- linux.orig/drivers/md/dm-linear.c
+++ linux/drivers/md/dm-linear.c
@@ -95,8 +95,8 @@ static int linear_map(struct dm_target *
 	return DM_MAPIO_REMAPPED;
 }
 
-static int linear_status(struct dm_target *ti, status_type_t type,
-			 unsigned status_flags, char *result, unsigned maxlen)
+static void linear_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct linear_c *lc = (struct linear_c *) ti->private;
 
@@ -110,7 +110,6 @@ static int linear_status(struct dm_targe
 				(unsigned long long)lc->start);
 		break;
 	}
-	return 0;
 }
 
 static int linear_ioctl(struct dm_target *ti, unsigned int cmd,
@@ -155,7 +154,7 @@ static int linear_iterate_devices(struct
 
 static struct target_type linear_target = {
 	.name   = "linear",
-	.version = {1, 2, 0},
+	.version = {1, 2, 1},
 	.module = THIS_MODULE,
 	.ctr    = linear_ctr,
 	.dtr    = linear_dtr,
Index: linux/drivers/md/dm-mpath.c
===================================================================
--- linux.orig/drivers/md/dm-mpath.c
+++ linux/drivers/md/dm-mpath.c
@@ -1378,8 +1378,8 @@ static void multipath_resume(struct dm_t
  *     [priority selector-name num_ps_args [ps_args]*
  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
  */
-static int multipath_status(struct dm_target *ti, status_type_t type,
-			    unsigned status_flags, char *result, unsigned maxlen)
+static void multipath_status(struct dm_target *ti, status_type_t type,
+			     unsigned status_flags, char *result, unsigned maxlen)
 {
 	int sz = 0;
 	unsigned long flags;
@@ -1485,8 +1485,6 @@ static int multipath_status(struct dm_ta
 	}
 
 	spin_unlock_irqrestore(&m->lock, flags);
-
-	return 0;
 }
 
 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
@@ -1695,7 +1693,7 @@ out:
  *---------------------------------------------------------------*/
 static struct target_type multipath_target = {
 	.name = "multipath",
-	.version = {1, 5, 0},
+	.version = {1, 5, 1},
 	.module = THIS_MODULE,
 	.ctr = multipath_ctr,
 	.dtr = multipath_dtr,
Index: linux/drivers/md/dm-raid.c
===================================================================
--- linux.orig/drivers/md/dm-raid.c
+++ linux/drivers/md/dm-raid.c
@@ -1201,8 +1201,8 @@ static int raid_map(struct dm_target *ti
 	return DM_MAPIO_SUBMITTED;
 }
 
-static int raid_status(struct dm_target *ti, status_type_t type,
-		       unsigned status_flags, char *result, unsigned maxlen)
+static void raid_status(struct dm_target *ti, status_type_t type,
+			unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct raid_set *rs = ti->private;
 	unsigned raid_param_cnt = 1; /* at least 1 for chunksize */
@@ -1344,8 +1344,6 @@ static int raid_status(struct dm_target 
 				DMEMIT(" -");
 		}
 	}
-
-	return 0;
 }
 
 static int raid_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
@@ -1405,7 +1403,7 @@ static void raid_resume(struct dm_target
 
 static struct target_type raid_target = {
 	.name = "raid",
-	.version = {1, 4, 1},
+	.version = {1, 4, 2},
 	.module = THIS_MODULE,
 	.ctr = raid_ctr,
 	.dtr = raid_dtr,
Index: linux/drivers/md/dm-raid1.c
===================================================================
--- linux.orig/drivers/md/dm-raid1.c
+++ linux/drivers/md/dm-raid1.c
@@ -1347,8 +1347,8 @@ static char device_status_char(struct mi
 }

-static int mirror_status(struct dm_target *ti, status_type_t type,
-			 unsigned status_flags, char *result, unsigned maxlen)
+static void mirror_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
 {
 	unsigned int m, sz = 0;
 	struct mirror_set *ms = (struct mirror_set *) ti->private;
@@ -1383,8 +1383,6 @@ static int mirror_status(struct dm_targe
 		if (ms->features & DM_RAID1_HANDLE_ERRORS)
 			DMEMIT(" 1 handle_errors");
 	}
-
-	return 0;
 }
 
 static int mirror_iterate_devices(struct dm_target *ti,
@@ -1403,7 +1401,7 @@ static int mirror_iterate_devices(struct
 
 static struct target_type mirror_target = {
 	.name	 = "mirror",
-	.version = {1, 13, 1},
+	.version = {1, 13, 2},
 	.module	 = THIS_MODULE,
 	.ctr	 = mirror_ctr,
 	.dtr	 = mirror_dtr,
Index: linux/drivers/md/dm-snap.c
===================================================================
--- linux.orig/drivers/md/dm-snap.c
+++ linux/drivers/md/dm-snap.c
@@ -1836,8 +1836,8 @@ static void snapshot_merge_resume(struct
 	start_merge(s);
 }
 
-static int snapshot_status(struct dm_target *ti, status_type_t type,
-			   unsigned status_flags, char *result, unsigned maxlen)
+static void snapshot_status(struct dm_target *ti, status_type_t type,
+			    unsigned status_flags, char *result, unsigned maxlen)
 {
 	unsigned sz = 0;
 	struct dm_snapshot *snap = ti->private;
@@ -1883,8 +1883,6 @@ static int snapshot_status(struct dm_tar
 					  maxlen - sz);
 		break;
 	}
-
-	return 0;
 }
 
 static int snapshot_iterate_devices(struct dm_target *ti,
@@ -2138,8 +2136,8 @@ static void origin_resume(struct dm_targ
 	ti->max_io_len = get_origin_minimum_chunksize(dev->bdev);
 }
 
-static int origin_status(struct dm_target *ti, status_type_t type,
-			 unsigned status_flags, char *result, unsigned maxlen)
+static void origin_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct dm_dev *dev = ti->private;
 
@@ -2152,8 +2150,6 @@ static int origin_status(struct dm_targe
 		snprintf(result, maxlen, "%s", dev->name);
 		break;
 	}
-
-	return 0;
 }
 
 static int origin_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
@@ -2180,7 +2176,7 @@ static int origin_iterate_devices(struct
 
 static struct target_type origin_target = {
 	.name    = "snapshot-origin",
-	.version = {1, 8, 0},
+	.version = {1, 8, 1},
 	.module  = THIS_MODULE,
 	.ctr     = origin_ctr,
 	.dtr     = origin_dtr,
@@ -2193,7 +2189,7 @@ static struct target_type origin_target 
 
 static struct target_type snapshot_target = {
 	.name    = "snapshot",
-	.version = {1, 11, 0},
+	.version = {1, 11, 1},
 	.module  = THIS_MODULE,
 	.ctr     = snapshot_ctr,
 	.dtr     = snapshot_dtr,
Index: linux/drivers/md/dm-stripe.c
===================================================================
--- linux.orig/drivers/md/dm-stripe.c
+++ linux/drivers/md/dm-stripe.c
@@ -312,8 +312,8 @@ static int stripe_map(struct dm_target *
  *
  */
 
-static int stripe_status(struct dm_target *ti, status_type_t type,
-			 unsigned status_flags, char *result, unsigned maxlen)
+static void stripe_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct stripe_c *sc = (struct stripe_c *) ti->private;
 	char buffer[sc->stripes + 1];
@@ -340,7 +340,6 @@ static int stripe_status(struct dm_targe
 			    (unsigned long long)sc->stripe[i].physical_start);
 		break;
 	}
-	return 0;
 }
 
 static int stripe_end_io(struct dm_target *ti, struct bio *bio, int error)
@@ -428,7 +427,7 @@ static int stripe_merge(struct dm_target
 
 static struct target_type stripe_target = {
 	.name   = "striped",
-	.version = {1, 5, 0},
+	.version = {1, 5, 1},
 	.module = THIS_MODULE,
 	.ctr    = stripe_ctr,
 	.dtr    = stripe_dtr,
Index: linux/drivers/md/dm-thin.c
===================================================================
--- linux.orig/drivers/md/dm-thin.c
+++ linux/drivers/md/dm-thin.c
@@ -2299,8 +2299,8 @@ static void emit_flags(struct pool_featu
  *    <transaction id> <used metadata sectors>/<total metadata sectors>
  *    <used data sectors>/<total data sectors> <held metadata root>
  */
-static int pool_status(struct dm_target *ti, status_type_t type,
-		       unsigned status_flags, char *result, unsigned maxlen)
+static void pool_status(struct dm_target *ti, status_type_t type,
+			unsigned status_flags, char *result, unsigned maxlen)
 {
 	int r;
 	unsigned sz = 0;
@@ -2326,32 +2326,41 @@ static int pool_status(struct dm_target 
 		if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti))
 			(void) commit_or_fallback(pool);
 
-		r = dm_pool_get_metadata_transaction_id(pool->pmd,
-							&transaction_id);
-		if (r)
-			return r;
-
-		r = dm_pool_get_free_metadata_block_count(pool->pmd,
-							  &nr_free_blocks_metadata);
-		if (r)
-			return r;
+		r = dm_pool_get_metadata_transaction_id(pool->pmd, &transaction_id);
+		if (r) {
+			DMERR("dm_pool_get_metadata_transaction_id returned %d", r);
+			goto err;
+		}
+
+		r = dm_pool_get_free_metadata_block_count(pool->pmd, &nr_free_blocks_metadata);
+		if (r) {
+			DMERR("dm_pool_get_free_metadata_block_count returned %d", r);
+			goto err;
+		}
 
 		r = dm_pool_get_metadata_dev_size(pool->pmd, &nr_blocks_metadata);
-		if (r)
-			return r;
+		if (r) {
+			DMERR("dm_pool_get_metadata_dev_size returned %d", r);
+			goto err;
+		}
 
-		r = dm_pool_get_free_block_count(pool->pmd,
-						 &nr_free_blocks_data);
-		if (r)
-			return r;
+		r = dm_pool_get_free_block_count(pool->pmd, &nr_free_blocks_data);
+		if (r) {
+			DMERR("dm_pool_get_free_block_count returned %d", r);
+			goto err;
+		}
 
 		r = dm_pool_get_data_dev_size(pool->pmd, &nr_blocks_data);
-		if (r)
-			return r;
+		if (r) {
+			DMERR("dm_pool_get_data_dev_size returned %d", r);
+			goto err;
+		}
 
 		r = dm_pool_get_metadata_snap(pool->pmd, &held_root);
-		if (r)
-			return r;
+		if (r) {
+			DMERR("dm_pool_get_metadata_snap returned %d", r);
+			goto err;
+		}
 
 		DMEMIT("%llu %llu/%llu %llu/%llu ",
 		       (unsigned long long)transaction_id,
@@ -2388,8 +2397,10 @@ static int pool_status(struct dm_target 
 		emit_flags(&pt->requested_pf, result, sz, maxlen);
 		break;
 	}
+	return;
 
-	return 0;
+err:
+	DMEMIT("Error");
 }
 
 static int pool_iterate_devices(struct dm_target *ti,
@@ -2468,7 +2479,7 @@ static struct target_type pool_target = 
 	.name = "thin-pool",
 	.features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
 		    DM_TARGET_IMMUTABLE,
-	.version = {1, 6, 0},
+	.version = {1, 6, 1},
 	.module = THIS_MODULE,
 	.ctr = pool_ctr,
 	.dtr = pool_dtr,
@@ -2676,8 +2687,8 @@ static void thin_postsuspend(struct dm_t
 /*
  * <nr mapped sectors> <highest mapped sector>
  */
-static int thin_status(struct dm_target *ti, status_type_t type,
-		       unsigned status_flags, char *result, unsigned maxlen)
+static void thin_status(struct dm_target *ti, status_type_t type,
+			unsigned status_flags, char *result, unsigned maxlen)
 {
 	int r;
 	ssize_t sz = 0;
@@ -2687,7 +2698,7 @@ static int thin_status(struct dm_target 
 
 	if (get_pool_mode(tc->pool) == PM_FAIL) {
 		DMEMIT("Fail");
-		return 0;
+		return;
 	}
 
 	if (!tc->td)
@@ -2696,12 +2707,16 @@ static int thin_status(struct dm_target 
 		switch (type) {
 		case STATUSTYPE_INFO:
 			r = dm_thin_get_mapped_count(tc->td, &mapped);
-			if (r)
-				return r;
+			if (r) {
+				DMERR("dm_thin_get_mapped_count returned %d", r);
+				goto err;
+			}
 
 			r = dm_thin_get_highest_mapped_block(tc->td, &highest);
-			if (r < 0)
-				return r;
+			if (r < 0) {
+				DMERR("dm_thin_get_highest_mapped_block returned %d", r);
+				goto err;
+			}
 
 			DMEMIT("%llu ", mapped * tc->pool->sectors_per_block);
 			if (r)
@@ -2721,7 +2736,10 @@ static int thin_status(struct dm_target 
 		}
 	}
 
-	return 0;
+	return;
+
+err:
+	DMEMIT("Error");
 }
 
 static int thin_iterate_devices(struct dm_target *ti,
@@ -2748,7 +2766,7 @@ static int thin_iterate_devices(struct d
 
 static struct target_type thin_target = {
 	.name = "thin",
-	.version = {1, 7, 0},
+	.version = {1, 7, 1},
 	.module	= THIS_MODULE,
 	.ctr = thin_ctr,
 	.dtr = thin_dtr,
Index: linux/drivers/md/dm-verity.c
===================================================================
--- linux.orig/drivers/md/dm-verity.c
+++ linux/drivers/md/dm-verity.c
@@ -508,8 +508,8 @@ static int verity_map(struct dm_target *
 /*
  * Status: V (valid) or C (corruption found)
  */
-static int verity_status(struct dm_target *ti, status_type_t type,
-			 unsigned status_flags, char *result, unsigned maxlen)
+static void verity_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
 {
 	struct dm_verity *v = ti->private;
 	unsigned sz = 0;
@@ -540,8 +540,6 @@ static int verity_status(struct dm_targe
 				DMEMIT("%02x", v->salt[x]);
 		break;
 	}
-
-	return 0;
 }
 
 static int verity_ioctl(struct dm_target *ti, unsigned cmd,
@@ -860,7 +858,7 @@ bad:
 
 static struct target_type verity_target = {
 	.name		= "verity",
-	.version	= {1, 1, 0},
+	.version	= {1, 1, 1},
 	.module		= THIS_MODULE,
 	.ctr		= verity_ctr,
 	.dtr		= verity_dtr,
Index: linux/include/linux/device-mapper.h
===================================================================
--- linux.orig/include/linux/device-mapper.h
+++ linux/include/linux/device-mapper.h
@@ -68,8 +68,8 @@ typedef void (*dm_postsuspend_fn) (struc
 typedef int (*dm_preresume_fn) (struct dm_target *ti);
 typedef void (*dm_resume_fn) (struct dm_target *ti);
 
-typedef int (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
-			     unsigned status_flags, char *result, unsigned maxlen);
+typedef void (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
+			      unsigned status_flags, char *result, unsigned maxlen);
 
 typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv);