netdev - Re: [PATCH net] mwifiex: Increase AES key storage size to 256 bits

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Date:   Tue, 25 Aug 2020 22:18:42 +0200
From:   Maximilian Luz <luzmaximilian@...il.com>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Amitkumar Karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi.bhat@....com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        netdev@...r.kernel.org,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Kaloyan Nikolov <konik98@...il.com>
Subject: Re: [PATCH net] mwifiex: Increase AES key storage size to 256 bits

On 8/25/20 9:30 PM, Brian Norris wrote:
> Also, while technically the regressing commit (e18696786548 ("mwifiex:
> Prevent memory corruption handling keys")) was fixing a potential
> overflow, the encasing command structure (struct host_cmd_ds_command)
> is a union of a ton of other command layouts, and likely had plenty of
> padding at the end, which would at least explain why non-malicious
> scenarios weren't problematic pre-commit-e18696786548.

This is pretty much spot on, although as far as I can tell, the padding
comes from struct mwifiex_ie_type_key_param_set_v2. That contains a
key_params member, which is a union over all supported key types,
including other 256 bit types (like struct mwifiex_wapi_param).

I should also note that this fix also affects mwifiex_set_aes_key_v2(),
where sizeof(struct mwifiex_aes_param) is used to calculate the command
length of what looks like a command being sent to the chip. This should
probably be reviewed by someone with a bit more inside knowledge about
the driver, as this could potentially break something due to the commit
changing it from 16 to 32. I think, however, that this might actually
also fix a potential issue when setting 256 bit AES keys.

Regards,
Max