linux-hardening - Re: [PATCH v2 3/3] wifi: mwifiex: Sanity check tlv_len and tlv_bitmap

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Date:   Fri, 25 Aug 2023 14:10:44 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Brian Norris <briannorris@...omium.org>,
        Kalle Valo <kvalo@...nel.org>,
        Amitkumar Karwar <akarwar@...vell.com>,
        Xinming Hu <huxm@...vell.com>, Dan Williams <dcbw@...hat.com>,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 3/3] wifi: mwifiex: Sanity check tlv_len and
 tlv_bitmap_len

On Thu, Aug 24, 2023 at 09:10:45PM -0600, Gustavo A. R. Silva wrote:
> Add sanity checks for both `tlv_len` and `tlv_bitmap_len` before
> decoding data from `event_buf`.
> 
> This prevents any malicious or buggy firmware from overflowing
> `event_buf` through large values for `tlv_len` and `tlv_bitmap_len`.
> 
> Suggested-by: Dan Williams <dcbw@...hat.com>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
> Changes in v2:
>  - Fix format specifier: %ld -> %zu
>    | Reported-by: kernel test robot <lkp@...el.com>
>    | Closes: https://lore.kernel.org/oe-kbuild-all/202308240844.leyoOwdG-lkp@intel.com/
> 
>  - Update warning messages to explicitly mention that TLV size is
>    greater than tlv_buf_len.
> 
> v1:
>  - Link: https://lore.kernel.org/linux-hardening/587423b0737108effe82aefed4407daca39e9a51.1692829410.git.gustavoars@kernel.org/
> 
>  .../net/wireless/marvell/mwifiex/11n_rxreorder.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c b/drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c
> index 735aac52bdc4..10690e82358b 100644
> --- a/drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c
> +++ b/drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c
> @@ -921,6 +921,14 @@ void mwifiex_11n_rxba_sync_event(struct mwifiex_private *priv,
>  	while (tlv_buf_left > sizeof(*tlv_rxba)) {
>  		tlv_type = le16_to_cpu(tlv_rxba->header.type);
>  		tlv_len  = le16_to_cpu(tlv_rxba->header.len);
> +		if (size_add(sizeof(tlv_rxba->header), tlv_len) > tlv_buf_left) {
> +			mwifiex_dbg(priv->adapter, WARN,
> +				    "TLV size (%zu) overflows event_buf buf_left=%d\n",
> +				    size_add(sizeof(tlv_rxba->header), tlv_len),
> +				    tlv_buf_left);

With the suggested change to make this a warning and not dbg:

Reviewed-by: Kees Cook <keescook@...omium.org>

Thanks!

-Kees

> +			return;
> +		}
> +
>  		if (tlv_type != TLV_TYPE_RXBA_SYNC) {
>  			mwifiex_dbg(priv->adapter, ERROR,
>  				    "Wrong TLV id=0x%x\n", tlv_type);
> @@ -929,6 +937,14 @@ void mwifiex_11n_rxba_sync_event(struct mwifiex_private *priv,
>  
>  		tlv_seq_num = le16_to_cpu(tlv_rxba->seq_num);
>  		tlv_bitmap_len = le16_to_cpu(tlv_rxba->bitmap_len);
> +		if (size_add(sizeof(*tlv_rxba), tlv_bitmap_len) > tlv_buf_left) {
> +			mwifiex_dbg(priv->adapter, WARN,
> +				    "TLV size (%zu) overflows event_buf buf_left=%d\n",
> +				    size_add(sizeof(*tlv_rxba), tlv_bitmap_len),
> +				    tlv_buf_left);
> +			return;
> +		}
> +
>  		mwifiex_dbg(priv->adapter, INFO,
>  			    "%pM tid=%d seq_num=%d bitmap_len=%d\n",
>  			    tlv_rxba->mac, tlv_rxba->tid, tlv_seq_num,
> -- 
> 2.34.1
> 

-- 
Kees Cook