linux-kernel - Re: [PATCH] nvdimm: btt_devs: fix a NULL pointer dereference and a memory leak

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Date:   Fri, 22 Mar 2019 15:55:10 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Kangjie Lu <kjlu@....edu>
Cc:     pakki001@....edu, Ross Zwisler <zwisler@...nel.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvdimm: btt_devs: fix a NULL pointer dereference and a
 memory leak

On Tue, Mar 12, 2019 at 1:16 AM Kangjie Lu <kjlu@....edu> wrote:
>
> In case kmemdup fails, the fix releases resources and returns to
> avoid the NULL pointer dereference.
> Also, the error paths in the following code should release
> resources to avoid memory leaks.
>
> Signed-off-by: Kangjie Lu <kjlu@....edu>
> ---
>  drivers/nvdimm/btt_devs.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvdimm/btt_devs.c b/drivers/nvdimm/btt_devs.c
> index 795ad4ff35ca..565ea0b6f765 100644
> --- a/drivers/nvdimm/btt_devs.c
> +++ b/drivers/nvdimm/btt_devs.c
> @@ -196,8 +196,13 @@ static struct device *__nd_btt_create(struct nd_region *nd_region,
>         }
>
>         nd_btt->lbasize = lbasize;
> -       if (uuid)
> +       if (uuid) {
>                 uuid = kmemdup(uuid, 16, GFP_KERNEL);
> +               if (!uuid) {
> +                       kfree(nd_btt);
> +                       return NULL;

What about nd_btt->id? That needs to be released as well.

> +               }
> +       }
>         nd_btt->uuid = uuid;
>         dev = &nd_btt->dev;
>         dev_set_name(dev, "btt%d.%d", nd_region->id, nd_btt->id);
> @@ -209,6 +214,7 @@ static struct device *__nd_btt_create(struct nd_region *nd_region,
>                 dev_dbg(&ndns->dev, "failed, already claimed by %s\n",
>                                 dev_name(ndns->claim));
>                 put_device(dev);
> +               kfree(uuid);

This will be a double free because put_device() will arrange for
nd_btt_release() to be called which does kfree(nd_btt->uuid);