Messages in this thread | | | Subject | Re: [PATCH 2/2] fs: btrfs: Don't leak memory when failing add fsid | From | Nikolay Borisov <> | Date | Mon, 13 May 2019 09:04:49 +0300 |
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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@kernel.org> > --- > 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) >
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