linux-kernel - Re: [PATCH] configfs: fix memleak in configfs_release_bin

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Date:   Tue, 22 Jun 2021 15:40:13 +0800
From:   Chung-Chiang Cheng <shepjeng@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     jlbec@...lplan.org,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Chung-Chiang Cheng <cccheng@...ology.com>
Subject: Re: [PATCH] configfs: fix memleak in configfs_release_bin_file

It works for me. I've verified it with ACPI configfs that is the only
one using configfs binary attributes so far, and the memleak issue
is solved.

On Tue, Jun 22, 2021 at 2:04 PM Christoph Hellwig <hch@....de> wrote:
>
> Hmm.  The issue looks real, but I think we should just call the vfree
> unconditionally given that the buffer structure is zeroed on allocation
> and freed just after, and also remove the pointless clearing of all the
> flags.  Does something like this work for you?
>
> diff --git a/fs/configfs/file.c b/fs/configfs/file.c
> index 53913b84383a..1ab6afb84f04 100644
> --- a/fs/configfs/file.c
> +++ b/fs/configfs/file.c
> @@ -393,11 +393,8 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)
>  {
>         struct configfs_buffer *buffer = file->private_data;
>
> -       buffer->read_in_progress = false;
> -
>         if (buffer->write_in_progress) {
>                 struct configfs_fragment *frag = to_frag(file);
> -               buffer->write_in_progress = false;
>
>                 down_read(&frag->frag_sem);
>                 if (!frag->frag_dead) {
> @@ -407,13 +404,9 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)
>                                         buffer->bin_buffer_size);
>                 }
>                 up_read(&frag->frag_sem);
> -               /* vfree on NULL is safe */
> -               vfree(buffer->bin_buffer);
> -               buffer->bin_buffer = NULL;
> -               buffer->bin_buffer_size = 0;
> -               buffer->needs_read_fill = 1;
>         }
>
> +       vfree(buffer->bin_buffer);
>         configfs_release(inode, file);
>         return 0;
>  }