[PATCH 20/43] btrfs: hold ref on root in btrfs_ioctl_default_subvol

Josef Bacik
2020-01-17T21:26:44Z

We look up an arbitrary fs root here, we need to hold a ref on the root
for the duration.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/ioctl.c | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7d30c7821490..69c39b3d15a5 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3987,7 +3987,7 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
struct btrfs_root *new_root;
struct btrfs_dir_item *di;
struct btrfs_trans_handle *trans;
- struct btrfs_path *path;
+ struct btrfs_path *path = NULL;
struct btrfs_key location;
struct btrfs_disk_key disk_key;
u64 objectid = 0;
@@ -4018,44 +4018,50 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
ret = PTR_ERR(new_root);
goto out;
}
- if (!is_fstree(new_root->root_key.objectid)) {
+ if (!btrfs_grab_fs_root(root)) {
ret = -ENOENT;
goto out;
}
+ if (!is_fstree(new_root->root_key.objectid)) {
+ ret = -ENOENT;
+ goto out_free;
+ }

path = btrfs_alloc_path();
if (!path) {
ret = -ENOMEM;
- goto out;
+ goto out_free;
}
path->leave_spinning = 1;

trans = btrfs_start_transaction(root, 1);
if (IS_ERR(trans)) {
- btrfs_free_path(path);
ret = PTR_ERR(trans);
- goto out;
+ goto out_free;
}

dir_id = btrfs_super_root_dir(fs_info->super_copy);
di = btrfs_lookup_dir_item(trans, fs_info->tree_root, path,
dir_id, "default", 7, 1);
if (IS_ERR_OR_NULL(di)) {
- btrfs_free_path(path);
+ btrfs_release_path(path);
btrfs_end_transaction(trans);
btrfs_err(fs_info,
"Umm, you don't have the default diritem, this isn't going to work");
ret = -ENOENT;
- goto out;
+ goto out_free;
}

btrfs_cpu_key_to_disk(&disk_key, &new_root->root_key);
btrfs_set_dir_item_key(path->nodes[0], di, &disk_key);
btrfs_mark_buffer_dirty(path->nodes[0]);
- btrfs_free_path(path);
+ btrfs_release_path(path);

btrfs_set_fs_incompat(fs_info, DEFAULT_SUBVOL);
btrfs_end_transaction(trans);
+out_free:
+ btrfs_put_fs_root(new_root);
+ btrfs_free_path(path);
out:
mnt_drop_write_file(file);
return ret;
--
2.24.1