Re: [PATCH] ext4: Fix memleak in add_new_gdb

From: Jan Kara
Date: Fri Aug 28 2020 - 05:21:25 EST


On Thu 27-08-20 14:28:43, Dinghao Liu wrote:
> When ext4_journal_get_write_access() fails, we should release
> n_group_desc, iloc.bh, dind and gdb_bh to prevent memleak.
> It's the same when ext4_handle_dirty_super() fails, but we
> don't need to release dind here because it has been released
> before.
>
> Signed-off-by: Dinghao Liu <dinghao.liu@xxxxxxxxxx>

Thanks for the patch! Some comments below:

> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index a50b51270ea9..efc0a022ca8e 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -843,8 +843,10 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
>
> BUFFER_TRACE(dind, "get_write_access");
> err = ext4_journal_get_write_access(handle, dind);
> - if (unlikely(err))
> + if (unlikely(err)) {
> ext4_std_error(sb, err);
> + goto errout;
> + }

This hunk looks good.

> @@ -899,13 +901,17 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
>
> le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
> err = ext4_handle_dirty_super(handle, sb);
> - if (err)
> + if (err) {
> ext4_std_error(sb, err);
> + goto errsuper;
> + }
> +
> return err;
> errout:
> + brelse(dind);
> +errsuper:

But this is definitely wrong. Look, n_group_desc and gdb_bh are already
referenced from the superblock so you cannot free them, iloc.bh has been
released in ext4_mark_iloc_dirty().

Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR