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SubjectRe: [PATCH] drivers: binderfs: fix memory leak in binderfs_fill_super
On Mon, Aug 15, 2022 at 02:46:36AM +0100, Al Viro wrote:
> On Fri, Aug 12, 2022 at 04:32:28PM +0200, Greg Kroah-Hartman wrote:
>
> > > It's a bit tricky to follow but d_make_root() always consumes the inode.
> > > On success via d_instantiate() and on failure via iput(). So when
> > > d_make_root() has been called the inode is off limits. And as soon as
> > > d_make_root() has returned successfully we're guaranteed that
> > > sb->s_fs_info is cleaned up if a ->put_super() method has been defined.
> > > Just fyi.
> >
> > Ah, thanks, that wasn't obvious at all.
> >
> > greg k-h
>
> FWIW, I would rather provide a proper ->kill_sb() and gotten rid of
> all that stuff. The thing is, unlike ->put_super(), ->kill_sb() is
> called for *anything* that has gotten to foo_fill_super(). Usually
> allows to get rid of those "call all of or parts of foo_put_super()
> on failure exits" and associated bitrot...
>
> Like this (completely untested):
>
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---

Sounds good,
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>

> diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
> index 588d753a7a19..c760f3129768 100644
> --- a/drivers/android/binderfs.c
> +++ b/drivers/android/binderfs.c
> @@ -340,22 +340,21 @@ static int binderfs_show_options(struct seq_file *seq, struct dentry *root)
> return 0;
> }
>
> -static void binderfs_put_super(struct super_block *sb)
> +static void binderfs_kill_super(struct super_block *sb)
> {
> struct binderfs_info *info = sb->s_fs_info;
>
> + kill_litter_super(sb);
> if (info && info->ipc_ns)
> put_ipc_ns(info->ipc_ns);
>
> kfree(info);
> - sb->s_fs_info = NULL;
> }
>
> static const struct super_operations binderfs_super_ops = {
> .evict_inode = binderfs_evict_inode,
> .show_options = binderfs_show_options,
> .statfs = simple_statfs,
> - .put_super = binderfs_put_super,
> };
>
> static inline bool is_binderfs_control_device(const struct dentry *dentry)
> @@ -789,7 +788,7 @@ static struct file_system_type binder_fs_type = {
> .name = "binder",
> .init_fs_context = binderfs_init_fs_context,
> .parameters = binderfs_fs_parameters,
> - .kill_sb = kill_litter_super,
> + .kill_sb = binderfs_kill_super,
> .fs_flags = FS_USERNS_MOUNT,
> };
>

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