On 13.05.19 г. 6:39 ч., Tobin C. Harding wrote:
> A failed call to kobject_init_and_add() must be followed by a call to
> kobject_put(). Currently in the error path when adding fs_devices we
> are missing this call. This could be fixed by calling
> btrfs_sysfs_remove_fsid() if btrfs_sysfs_add_fsid() returns an error or
> by adding a call to kobject_put() directly in btrfs_sysfs_add_fsid().
> Here we choose the second option because it prevents the slightly
> unusual error path handling requirements of kobject from leaking out
> into btrfs functions.
>
> Add a call to kobject_put() in the error path of kobject_add_and_init().
> This causes the release method to be called if kobject_init_and_add()
> fails. open_tree() is the function that calls btrfs_sysfs_add_fsid()
> and the error code in this function is already written with the
> assumption that the release method is called during the error path of
> open_tree() (as seen by the call to btrfs_sysfs_remove_fsid() under the
> fail_fsdev_sysfs label).
I'm not familiar with the internals of kobject but
btrfs_sysfs_remove_fsid calls __btrfs_sysfs_remove_fsid which in turn
does kobject_del followed by kobject_put so its sequence is not exactly
identical with your change. Presumably kobject_del is only required if
you want to dispose of successfully registered sysfs node. This implies
that __btrfs_sysfs_remove_fsid is actually broken when it comes to
handling failed sysfs_add_fsid?
>
> Signed-off-by: Tobin C. Harding <tobin@xxxxxxxxxx>
> ---
> fs/btrfs/sysfs.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 5a5930e3d32b..2f078b77fe14 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -825,7 +825,12 @@ int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs,
> fs_devs->fsid_kobj.kset = btrfs_kset;
> error = kobject_init_and_add(&fs_devs->fsid_kobj,
> &btrfs_ktype, parent, "%pU", fs_devs->fsid);
> - return error;
> + if (error) {
> + kobject_put(&fs_devs->fsid_kobj);
> + return error;
> + }
> +
> + return 0;
> }
>
> int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
>
