[PATCH AUTOSEL 6.10 22/27] btrfs: do not BUG_ON() when freeing tree block after error

Sasha Levin
2024-07-28T00:54:27Z

From: Filipe Manana <fdmanana@suse.com>

[ Upstream commit bb3868033a4cccff7be57e9145f2117cbdc91c11 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/ctree.c | 53 ++++++++++++++++++++++++++++++--------
fs/btrfs/extent-tree.c | 24 ++++++++++-------
fs/btrfs/extent-tree.h | 8 +++---
fs/btrfs/free-space-tree.c | 10 ++++---
fs/btrfs/ioctl.c | 6 ++++-
fs/btrfs/qgroup.c | 6 +++--
6 files changed, 76 insertions(+), 31 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 1a49b92329908..ca372068226d5 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -620,10 +620,16 @@ int btrfs_force_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,
@@ -648,8 +654,14 @@ int btrfs_force_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);
@@ -983,9 +995,13 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
free_extent_buffer(mid);

root_sub_used_bytes(root);
- 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) >
@@ -1053,10 +1069,14 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
goto out;
}
root_sub_used_bytes(root);
- btrfs_free_tree_block(trans, btrfs_root_id(root), right,
- 0, 1);
+ 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);
@@ -1111,9 +1131,13 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
goto out;
}
root_sub_used_bytes(root);
- 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;
@@ -2883,7 +2907,11 @@ 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;
@@ -4452,9 +4480,12 @@ static noinline int btrfs_del_leaf(struct btrfs_trans_handle *trans,
root_sub_used_bytes(root);

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 3774c191e36dc..41db538e4959e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3419,10 +3419,10 @@ static noinline int check_ref_cleanup(struct btrfs_trans_handle *trans,
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_block_group *bg;
@@ -3449,11 +3449,12 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
btrfs_init_tree_ref(&generic_ref, btrfs_header_level(buf), 0, false);
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)
- return;
+ return 0;

if (btrfs_header_generation(buf) != trans->transid)
goto out;
@@ -3510,6 +3511,7 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
* matter anymore.
*/
clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
+ return 0;
}

/* Can return -ENOMEM */
@@ -5643,7 +5645,7 @@ 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;
@@ -5730,12 +5732,14 @@ 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 af9f8800d5aca..2ad51130c037e 100644
--- a/fs/btrfs/extent-tree.h
+++ b/fs/btrfs/extent-tree.h
@@ -127,10 +127,10 @@ struct extent_buffer *btrfs_alloc_tree_block(struct btrfs_trans_handle *trans,
u64 empty_size,
u64 reloc_src_root,
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 90f2938bd743d..7ba50e133921a 100644
--- a/fs/btrfs/free-space-tree.c
+++ b/fs/btrfs/free-space-tree.c
@@ -1300,10 +1300,14 @@ 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 efd5d6e9589e0..c1b0556e40368 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -719,6 +719,8 @@ 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
@@ -729,7 +731,9 @@ 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 39a15cca58ca9..29d6ca3b874ec 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1446,9 +1446,11 @@ 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);
--
2.43.0