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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Mon, 21 Sep 2020 22:16:44 -0700
Message-ID: <CABBYNZKTQeZZkVCGaCvnL661Qsxc1cFGNggEuM3pD7p0S8yRwQ@mail.gmail.com>
Subject: Re: [PATCH v1] Bluetooth: btintel: Fix issue reported by static
 analysis tool
To:     Kiran K <kiraank@gmail.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        Chethan T N <chethan.tumkur.narayan@intel.com>,
        ravishankar.srivatsa@intel.com, dan.carpenter@oracle.com,
        Kiran K <kiran.k@intel.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Kiran,

On Mon, Sep 21, 2020 at 9:03 PM Kiran K <kiraank@gmail.com> wrote:
>
> Smatch tool reported the below issue:
>
> drivers/bluetooth/btintel.c:490 btintel_read_version_tlv()
> error: 'tlv->len' from user is not capped properly
>
> Additional details in the below link
> https://www.spinics.net/lists/linux-bluetooth/msg87786.html
>
> Signed-off-by: Kiran K <kiran.k@intel.com>
> ---
>  drivers/bluetooth/btintel.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/bluetooth/btintel.c b/drivers/bluetooth/btintel.c
> index 88ce5f0..47f2b3d 100644
> --- a/drivers/bluetooth/btintel.c
> +++ b/drivers/bluetooth/btintel.c
> @@ -431,62 +431,99 @@ int btintel_read_version_tlv(struct hci_dev *hdev, struct intel_version_tlv *ver
>          * version field like hw_platform, hw_variant, and fw_variant
>          * to keep the existing setup flow
>          */
> -       while (skb->len) {
> +       while (skb->len >= sizeof(struct intel_tlv)) {
>                 struct intel_tlv *tlv;
>
>                 tlv = (struct intel_tlv *)skb->data;
> +               if (struct_size(tlv, val, tlv->len) > skb->len)
> +                       goto failed;
> +
>                 switch (tlv->type) {
>                 case INTEL_TLV_CNVI_TOP:
> +                       if (tlv->len < sizeof(u32))
> +                               goto failed;
>                         version->cnvi_top = get_unaligned_le32(tlv->val);
>                         break;
>                 case INTEL_TLV_CNVR_TOP:
> +                       if (tlv->len < sizeof(u32))
> +                               goto failed;
>                         version->cnvr_top = get_unaligned_le32(tlv->val);
>                         break;
>                 case INTEL_TLV_CNVI_BT:
> +                       if (tlv->len < sizeof(u32))
> +                               goto failed;
>                         version->cnvi_bt = get_unaligned_le32(tlv->val);
>                         break;
>                 case INTEL_TLV_CNVR_BT:
> +                       if (tlv->len < sizeof(u32))
> +                               goto failed;
>                         version->cnvr_bt = get_unaligned_le32(tlv->val);
>                         break;
>                 case INTEL_TLV_DEV_REV_ID:
> +                       if (tlv->len < sizeof(u16))
> +                               goto failed;
>                         version->dev_rev_id = get_unaligned_le16(tlv->val);
>                         break;
>                 case INTEL_TLV_IMAGE_TYPE:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->img_type = tlv->val[0];
>                         break;
>                 case INTEL_TLV_TIME_STAMP:
> +                       if (tlv->len < sizeof(u16))
> +                               goto failed;
>                         version->timestamp = get_unaligned_le16(tlv->val);
>                         break;
>                 case INTEL_TLV_BUILD_TYPE:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->build_type = tlv->val[0];
>                         break;
>                 case INTEL_TLV_BUILD_NUM:
> +                       if (tlv->len < sizeof(u32))
> +                               goto failed;
>                         version->build_num = get_unaligned_le32(tlv->val);
>                         break;
>                 case INTEL_TLV_SECURE_BOOT:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->secure_boot = tlv->val[0];
>                         break;
>                 case INTEL_TLV_OTP_LOCK:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->otp_lock = tlv->val[0];
>                         break;
>                 case INTEL_TLV_API_LOCK:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->api_lock = tlv->val[0];
>                         break;
>                 case INTEL_TLV_DEBUG_LOCK:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->debug_lock = tlv->val[0];
>                         break;
>                 case INTEL_TLV_MIN_FW:
> +                       if (tlv->len < 3)
> +                               goto failed;
>                         version->min_fw_build_nn = tlv->val[0];
>                         version->min_fw_build_cw = tlv->val[1];
>                         version->min_fw_build_yy = tlv->val[2];
>                         break;
>                 case INTEL_TLV_LIMITED_CCE:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->limited_cce = tlv->val[0];
>                         break;
>                 case INTEL_TLV_SBE_TYPE:
> +                       if (tlv->len < sizeof(u8))
> +                               goto failed;
>                         version->sbe_type = tlv->val[0];
>                         break;
>                 case INTEL_TLV_OTP_BDADDR:
> +                       if (tlv->len != sizeof(version->otp_bd_addr))
> +                               goto failed;

Do we really want to fail here? The advantage of using a TLV is that
we can skip if the type is not understood or is malformed but with
this checks the length becomes useless since the types will always
have a fixed value, also we cannot extend the types later on since it
would not be backward compatible if we maintain such strict checks.

>                         memcpy(&version->otp_bd_addr, tlv->val, tlv->len);
>                         break;
>                 default:
> @@ -499,6 +536,10 @@ int btintel_read_version_tlv(struct hci_dev *hdev, struct intel_version_tlv *ver
>
>         kfree_skb(skb);
>         return 0;
> +
> +failed:
> +       kfree_skb(skb);
> +       return -EINVAL;
>  }
>  EXPORT_SYMBOL_GPL(btintel_read_version_tlv);
>
> --
> 2.7.4
>


-- 
Luiz Augusto von Dentz