dm persistent data: handle space map checker creation failure

If CONFIG_DM_DEBUG_SPACE_MAPS is enabled and dm_sm_checker_create()
fails, dm_tm_create_internal() would still return success even though it
cleaned up all resources it was supposed to have created.  This will
lead to a kernel crash:

general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC
...
RIP: 0010:[<ffffffff81593659>]  [<ffffffff81593659>] dm_bufio_get_block_size+0x9/0x20
Call Trace:
  [<ffffffff81599bae>] dm_bm_block_size+0xe/0x10
  [<ffffffff8159b8b8>] sm_ll_init+0x78/0xd0
  [<ffffffff8159c1a6>] sm_ll_new_disk+0x16/0xa0
  [<ffffffff8159c98e>] dm_sm_disk_create+0xfe/0x160
  [<ffffffff815abf6e>] dm_pool_metadata_open+0x16e/0x6a0
  [<ffffffff815aa010>] pool_ctr+0x3f0/0x900
  [<ffffffff8158d565>] dm_table_add_target+0x195/0x450
  [<ffffffff815904c4>] table_load+0xe4/0x330
  [<ffffffff815917ea>] ctl_ioctl+0x15a/0x2c0
  [<ffffffff81591963>] dm_ctl_ioctl+0x13/0x20
  [<ffffffff8116a4f8>] do_vfs_ioctl+0x98/0x560
  [<ffffffff8116aa51>] sys_ioctl+0x91/0xa0
  [<ffffffff81869f52>] system_call_fastpath+0x16/0x1b

Fix the space map checker code to return an appropriate ERR_PTR and have
dm_sm_disk_create() and dm_tm_create_internal() check for it with
IS_ERR.
Reported-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/persistent-data/dm-space-map-checker.c

@@ -343,25 +343,25 @@ struct dm_space_map *dm_sm_checker_create(struct dm_space_map *sm)
 	int r;
 	struct sm_checker *smc;
 
-	if (!sm)
-		return NULL;
+	if (IS_ERR_OR_NULL(sm))
+		return ERR_PTR(-EINVAL);
 
 	smc = kmalloc(sizeof(*smc), GFP_KERNEL);
 	if (!smc)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	memcpy(&smc->sm, &ops_, sizeof(smc->sm));
 	r = ca_create(&smc->old_counts, sm);
 	if (r) {
 		kfree(smc);
-		return NULL;
+		return ERR_PTR(r);
 	}
 
 	r = ca_create(&smc->counts, sm);
 	if (r) {
 		ca_destroy(&smc->old_counts);
 		kfree(smc);
-		return NULL;
+		return ERR_PTR(r);
 	}
 
 	smc->real_sm = sm;
@@ -371,7 +371,7 @@ struct dm_space_map *dm_sm_checker_create(struct dm_space_map *sm)
 		ca_destroy(&smc->counts);
 		ca_destroy(&smc->old_counts);
 		kfree(smc);
-		return NULL;
+		return ERR_PTR(r);
 	}
 
 	r = ca_commit(&smc->old_counts, &smc->counts);
@@ -379,7 +379,7 @@ struct dm_space_map *dm_sm_checker_create(struct dm_space_map *sm)
 		ca_destroy(&smc->counts);
 		ca_destroy(&smc->old_counts);
 		kfree(smc);
-		return NULL;
+		return ERR_PTR(r);
 	}
 
 	return &smc->sm;
@@ -391,25 +391,25 @@ struct dm_space_map *dm_sm_checker_create_fresh(struct dm_space_map *sm)
 	int r;
 	struct sm_checker *smc;
 
-	if (!sm)
-		return NULL;
+	if (IS_ERR_OR_NULL(sm))
+		return ERR_PTR(-EINVAL);
 
 	smc = kmalloc(sizeof(*smc), GFP_KERNEL);
 	if (!smc)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	memcpy(&smc->sm, &ops_, sizeof(smc->sm));
 	r = ca_create(&smc->old_counts, sm);
 	if (r) {
 		kfree(smc);
-		return NULL;
+		return ERR_PTR(r);
 	}
 
 	r = ca_create(&smc->counts, sm);
 	if (r) {
 		ca_destroy(&smc->old_counts);
 		kfree(smc);
-		return NULL;
+		return ERR_PTR(r);
 	}
 
 	smc->real_sm = sm;

drivers/md/persistent-data/dm-space-map-disk.c

@@ -290,7 +290,16 @@ struct dm_space_map *dm_sm_disk_create(struct dm_transaction_manager *tm,
 				       dm_block_t nr_blocks)
 {
 	struct dm_space_map *sm = dm_sm_disk_create_real(tm, nr_blocks);
-	return dm_sm_checker_create_fresh(sm);
+	struct dm_space_map *smc;
+
+	if (IS_ERR_OR_NULL(sm))
+		return sm;
+
+	smc = dm_sm_checker_create_fresh(sm);
+	if (IS_ERR(smc))
+		dm_sm_destroy(sm);
+
+	return smc;
 }
 EXPORT_SYMBOL_GPL(dm_sm_disk_create);
 

drivers/md/persistent-data/dm-transaction-manager.c

@@ -347,8 +347,10 @@ static int dm_tm_create_internal(struct dm_block_manager *bm,
 		}
 
 		*sm = dm_sm_checker_create(inner);
-		if (!*sm)
+		if (IS_ERR(*sm)) {
+			r = PTR_ERR(*sm);
 			goto bad2;
+		}
 
 	} else {
 		r = dm_bm_write_lock(dm_tm_get_bm(*tm), sb_location,
@@ -367,8 +369,10 @@ static int dm_tm_create_internal(struct dm_block_manager *bm,
 		}
 
 		*sm = dm_sm_checker_create(inner);
-		if (!*sm)
+		if (IS_ERR(*sm)) {
+			r = PTR_ERR(*sm);
 			goto bad2;
+		}
 	}
 
 	return 0;