btrfs: do not BUG_ON() when freeing tree block after error

commit bb3868033a4cccff7be57e9145f2117cbdc91c11 upstream.

When freeing a tree block, at btrfs_free_tree_block(), if we fail to
create a delayed reference we don't deal with the error and just do a
BUG_ON(). The error most likely to happen is -ENOMEM, and we have a
comment mentioning that only -ENOMEM can happen, but that is not true,
because in case qgroups are enabled any error returned from
btrfs_qgroup_trace_extent_post() (can be -EUCLEAN or anything returned
from btrfs_search_slot() for example) can be propagated back to
btrfs_free_tree_block().

So stop doing a BUG_ON() and return the error to the callers and make
them abort the transaction to prevent leaking space. Syzbot was
triggering this, likely due to memory allocation failure injection.

Reported-by: syzbot+a306f914b4d01b3958fe@syzkaller.appspotmail.com
Link: https://lore.kernel.org/linux-btrfs/000000000000fcba1e05e998263c@google.com/
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[ Resolve minor conflicts ]
Signed-off-by: Bin Lan <bin.lan.cn@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

6 files changed, 74 insertions, 29 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 2eb4e03080ac..bb5d317fcdbe 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -617,10 +617,16 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 		atomic_inc(&cow->refs);
 		rcu_assign_pointer(root->node, cow);
 
-		btrfs_free_tree_block(trans, btrfs_root_id(root), buf,
-				      parent_start, last_ref);
+		ret = btrfs_free_tree_block(trans, btrfs_root_id(root), buf,
+					    parent_start, last_ref);
 		free_extent_buffer(buf);
 		add_root_to_dirty_list(root);
+		if (ret < 0) {
+			btrfs_tree_unlock(cow);
+			free_extent_buffer(cow);
+			btrfs_abort_transaction(trans, ret);
+			return ret;
+		}
 	} else {
 		WARN_ON(trans->transid != btrfs_header_generation(parent));
 		ret = btrfs_tree_mod_log_insert_key(parent, parent_slot,
@@ -645,8 +651,14 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 				return ret;
 			}
 		}
-		btrfs_free_tree_block(trans, btrfs_root_id(root), buf,
-				      parent_start, last_ref);
+		ret = btrfs_free_tree_block(trans, btrfs_root_id(root), buf,
+					    parent_start, last_ref);
+		if (ret < 0) {
+			btrfs_tree_unlock(cow);
+			free_extent_buffer(cow);
+			btrfs_abort_transaction(trans, ret);
+			return ret;
+		}
 	}
 	if (unlock_orig)
 		btrfs_tree_unlock(buf);
@@ -1121,9 +1133,13 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		free_extent_buffer(mid);
 
 		root_sub_used(root, mid->len);
-		btrfs_free_tree_block(trans, btrfs_root_id(root), mid, 0, 1);
+		ret = btrfs_free_tree_block(trans, btrfs_root_id(root), mid, 0, 1);
 		/* once for the root ptr */
 		free_extent_buffer_stale(mid);
+		if (ret < 0) {
+			btrfs_abort_transaction(trans, ret);
+			goto out;
+		}
 		return 0;
 	}
 	if (btrfs_header_nritems(mid) >
@@ -1191,10 +1207,14 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 				goto out;
 			}
 			root_sub_used(root, right->len);
-			btrfs_free_tree_block(trans, btrfs_root_id(root), right,
+			ret = btrfs_free_tree_block(trans, btrfs_root_id(root), right,
 					      0, 1);
 			free_extent_buffer_stale(right);
 			right = NULL;
+			if (ret < 0) {
+				btrfs_abort_transaction(trans, ret);
+				goto out;
+			}
 		} else {
 			struct btrfs_disk_key right_key;
 			btrfs_node_key(right, &right_key, 0);
@@ -1249,9 +1269,13 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 			goto out;
 		}
 		root_sub_used(root, mid->len);
-		btrfs_free_tree_block(trans, btrfs_root_id(root), mid, 0, 1);
+		ret = btrfs_free_tree_block(trans, btrfs_root_id(root), mid, 0, 1);
 		free_extent_buffer_stale(mid);
 		mid = NULL;
+		if (ret < 0) {
+			btrfs_abort_transaction(trans, ret);
+			goto out;
+		}
 	} else {
 		/* update the parent key to reflect our changes */
 		struct btrfs_disk_key mid_key;
@@ -3022,7 +3046,11 @@ static noinline int insert_new_root(struct btrfs_trans_handle *trans,
 	old = root->node;
 	ret = btrfs_tree_mod_log_insert_root(root->node, c, false);
 	if (ret < 0) {
-		btrfs_free_tree_block(trans, btrfs_root_id(root), c, 0, 1);
+		int ret2;
+
+		ret2 = btrfs_free_tree_block(trans, btrfs_root_id(root), c, 0, 1);
+		if (ret2 < 0)
+			btrfs_abort_transaction(trans, ret2);
 		btrfs_tree_unlock(c);
 		free_extent_buffer(c);
 		return ret;
@@ -4587,9 +4615,12 @@ static noinline int btrfs_del_leaf(struct btrfs_trans_handle *trans,
 	root_sub_used(root, leaf->len);
 
 	atomic_inc(&leaf->refs);
-	btrfs_free_tree_block(trans, btrfs_root_id(root), leaf, 0, 1);
+	ret = btrfs_free_tree_block(trans, btrfs_root_id(root), leaf, 0, 1);
 	free_extent_buffer_stale(leaf);
-	return 0;
+	if (ret < 0)
+		btrfs_abort_transaction(trans, ret);
+
+	return ret;
 }
 /*
  * delete the item at the leaf level in path.  If that empties
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index b3680e1c7054..94fc86c9c65e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3290,10 +3290,10 @@ out_delayed_unlock:
 	return 0;
 }
 
-void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
-			   u64 root_id,
-			   struct extent_buffer *buf,
-			   u64 parent, int last_ref)
+int btrfs_free_tree_block(struct btrfs_trans_handle *trans,
+			  u64 root_id,
+			  struct extent_buffer *buf,
+			  u64 parent, int last_ref)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
 	struct btrfs_ref generic_ref = { 0 };
@@ -3307,7 +3307,8 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
 	if (root_id != BTRFS_TREE_LOG_OBJECTID) {
 		btrfs_ref_tree_mod(fs_info, &generic_ref);
 		ret = btrfs_add_delayed_tree_ref(trans, &generic_ref, NULL);
-		BUG_ON(ret); /* -ENOMEM */
+		if (ret < 0)
+			return ret;
 	}
 
 	if (last_ref && btrfs_header_generation(buf) == trans->transid) {
@@ -3371,6 +3372,7 @@ out:
 		 */
 		clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
 	}
+	return 0;
 }
 
 /* Can return -ENOMEM */
@@ -5474,7 +5476,7 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
 				 struct walk_control *wc)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
-	int ret;
+	int ret = 0;
 	int level = wc->level;
 	struct extent_buffer *eb = path->nodes[level];
 	u64 parent = 0;
@@ -5565,12 +5567,14 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
 			goto owner_mismatch;
 	}
 
-	btrfs_free_tree_block(trans, btrfs_root_id(root), eb, parent,
-			      wc->refs[level] == 1);
+	ret = btrfs_free_tree_block(trans, btrfs_root_id(root), eb, parent,
+				    wc->refs[level] == 1);
+	if (ret < 0)
+		btrfs_abort_transaction(trans, ret);
 out:
 	wc->refs[level] = 0;
 	wc->flags[level] = 0;
-	return 0;
+	return ret;
 
 owner_mismatch:
 	btrfs_err_rl(fs_info, "unexpected tree owner, have %llu expect %llu",
diff --git a/fs/btrfs/extent-tree.h b/fs/btrfs/extent-tree.h
index 88c249c37516..ef1c1c99294e 100644
--- a/fs/btrfs/extent-tree.h
+++ b/fs/btrfs/extent-tree.h
@@ -114,10 +114,10 @@ struct extent_buffer *btrfs_alloc_tree_block(struct btrfs_trans_handle *trans,
 					     int level, u64 hint,
 					     u64 empty_size,
 					     enum btrfs_lock_nesting nest);
-void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
-			   u64 root_id,
-			   struct extent_buffer *buf,
-			   u64 parent, int last_ref);
+int btrfs_free_tree_block(struct btrfs_trans_handle *trans,
+			  u64 root_id,
+			  struct extent_buffer *buf,
+			  u64 parent, int last_ref);
 int btrfs_alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
 				     struct btrfs_root *root, u64 owner,
 				     u64 offset, u64 ram_bytes,
diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c
index 7b598b070700..a0d8160b5375 100644
--- a/fs/btrfs/free-space-tree.c
+++ b/fs/btrfs/free-space-tree.c
@@ -1289,10 +1289,14 @@ int btrfs_delete_free_space_tree(struct btrfs_fs_info *fs_info)
 	btrfs_tree_lock(free_space_root->node);
 	btrfs_clear_buffer_dirty(trans, free_space_root->node);
 	btrfs_tree_unlock(free_space_root->node);
-	btrfs_free_tree_block(trans, btrfs_root_id(free_space_root),
-			      free_space_root->node, 0, 1);
-
+	ret = btrfs_free_tree_block(trans, btrfs_root_id(free_space_root),
+				    free_space_root->node, 0, 1);
 	btrfs_put_root(free_space_root);
+	if (ret < 0) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		return ret;
+	}
 
 	return btrfs_commit_transaction(trans);
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 5f0c9c3f3bbf..ae6806bc3929 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -707,6 +707,8 @@ static noinline int create_subvol(struct mnt_idmap *idmap,
 	ret = btrfs_insert_root(trans, fs_info->tree_root, &key,
 				root_item);
 	if (ret) {
+		int ret2;
+
 		/*
 		 * Since we don't abort the transaction in this case, free the
 		 * tree block so that we don't leak space and leave the
@@ -717,7 +719,9 @@ static noinline int create_subvol(struct mnt_idmap *idmap,
 		btrfs_tree_lock(leaf);
 		btrfs_clear_buffer_dirty(trans, leaf);
 		btrfs_tree_unlock(leaf);
-		btrfs_free_tree_block(trans, objectid, leaf, 0, 1);
+		ret2 = btrfs_free_tree_block(trans, objectid, leaf, 0, 1);
+		if (ret2 < 0)
+			btrfs_abort_transaction(trans, ret2);
 		free_extent_buffer(leaf);
 		goto out;
 	}
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 74b82390fe84..1b9f4f16d124 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1320,9 +1320,11 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
 	btrfs_tree_lock(quota_root->node);
 	btrfs_clear_buffer_dirty(trans, quota_root->node);
 	btrfs_tree_unlock(quota_root->node);
-	btrfs_free_tree_block(trans, btrfs_root_id(quota_root),
-			      quota_root->node, 0, 1);
+	ret = btrfs_free_tree_block(trans, btrfs_root_id(quota_root),
+				    quota_root->node, 0, 1);
 
+	if (ret < 0)
+		btrfs_abort_transaction(trans, ret);
 
 out:
 	btrfs_put_root(quota_root);