linux-kernel - Re: [PATCH v4] Bluetooth: btmtk: Fix null pointer when processing coredump

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Message-ID: <CABBYNZLoJtUpAR-yKpq9a1NCTjhdgWMNSdwGd7f9jtFR0LuEAA@mail.gmail.com>
Date:   Wed, 12 Jul 2023 13:29:47 -0700
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     Chris Lu <chris.lu@...iatek.com>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Aaron Hou <aaron.hou@...iatek.com>,
        Steve Lee <steve.lee@...iatek.com>,
        linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-mediatek <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v4] Bluetooth: btmtk: Fix null pointer when processing coredump

Hi Chris,

On Wed, Jul 12, 2023 at 6:03 AM Chris Lu <chris.lu@...iatek.com> wrote:
>
> There may be a potential null pointer risk if offset value is
> less than 0 when doing memcmp in btmtk_process_coredump().
> Check offset is valid before doing memcmp.
>
> Signed-off-by: Chris Lu <chris.lu@...iatek.com>
> Co-developed-by: Sean Wang <sean.wang@...iatek.com>
> Signed-off-by: Sean Wang <sean.wang@...iatek.com>

You should probably include the Fixes tag of the patch that introduced
the problem.

> ---
> v2: fix typo
> v3: fix bot checking error
> v4: reduce variable 'offset' declaration in v3
> ---
>  drivers/bluetooth/btmtk.c | 12 ++++++------
>  drivers/bluetooth/btmtk.h |  1 +
>  2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
> index 786f775196ae..9cc789272ab7 100644
> --- a/drivers/bluetooth/btmtk.c
> +++ b/drivers/bluetooth/btmtk.c
> @@ -395,12 +395,12 @@ int btmtk_process_coredump(struct hci_dev *hdev, struct sk_buff *skb)
>
>                 /* Mediatek coredump data would be more than MTK_COREDUMP_NUM */
>                 if (data->cd_info.cnt > MTK_COREDUMP_NUM &&
> -                   skb->len > sizeof(MTK_COREDUMP_END) &&
> -                   !memcmp((char *)&skb->data[skb->len - sizeof(MTK_COREDUMP_END)],
> -                           MTK_COREDUMP_END, sizeof(MTK_COREDUMP_END) - 1)) {
> -                       bt_dev_info(hdev, "Mediatek coredump end");
> -                       hci_devcd_complete(hdev);
> -               }
> +                   skb->len > MTK_COREDUMP_END_LEN)
> +                       if (!memcmp((char *)&skb->data[skb->len - MTK_COREDUMP_END_LEN],
> +                           MTK_COREDUMP_END, MTK_COREDUMP_END_LEN - 1)) {
> +                               bt_dev_info(hdev, "Mediatek coredump end");
> +                               hci_devcd_complete(hdev);
> +                       }
>
>                 break;
>         }
> diff --git a/drivers/bluetooth/btmtk.h b/drivers/bluetooth/btmtk.h
> index 68309dfe076a..56f5502baadf 100644
> --- a/drivers/bluetooth/btmtk.h
> +++ b/drivers/bluetooth/btmtk.h
> @@ -24,6 +24,7 @@
>
>  #define MTK_COREDUMP_SIZE              (1024 * 1000)
>  #define MTK_COREDUMP_END               "coredump end"
> +#define MTK_COREDUMP_END_LEN           (sizeof(MTK_COREDUMP_END))
>  #define MTK_COREDUMP_NUM               255
>
>  enum {
> --
> 2.18.0
>


-- 
Luiz Augusto von Dentz