Re: [PATCH] mwifiex: drop most magic numbers from mwifiex_process_tdls_action_frame()

From: Kalle Valo <kvalo@codeaurora.org>
To: Brian Norris <briannorris@chromium.org>
Cc: linux-wireless@vger.kernel.org, <linux-kernel@vger.kernel.org>,
	Ganapathi Bhat <ganapathi.bhat@nxp.com>,
	Nishant Sarmukadam <nishants@marvell.com>,
	Amitkumar Karwar <amitkarwar@gmail.com>,
	Xinming Hu <huxinming820@gmail.com>,
	dan.carpenter@oracle.com, solar@openwall.com,
	wangqize888888888@gmail.com,
	Brian Norris <briannorris@chromium.org>
Subject: Re: [PATCH] mwifiex: drop most magic numbers from mwifiex_process_tdls_action_frame()
Date: Sun, 26 Jan 2020 11:37:22 +0000 (UTC)	[thread overview]
Message-ID: <20200126113722.D8991C4479C@smtp.codeaurora.org> (raw)
In-Reply-To: <20191206194535.150179-1-briannorris@chromium.org>

Brian Norris <briannorris@chromium.org> wrote:

> Before commit 1e58252e334d ("mwifiex: Fix heap overflow in
> mmwifiex_process_tdls_action_frame()"),
> mwifiex_process_tdls_action_frame() already had too many magic numbers.
> But this commit just added a ton more, in the name of checking for
> buffer overflows. That seems like a really bad idea.
> 
> Let's make these magic numbers a little less magic, by
> (a) factoring out 'pos[1]' as 'ie_len'
> (b) using 'sizeof' on the appropriate source or destination fields where
>     possible, instead of bare numbers
> (c) dropping redundant checks, per below.
> 
> Regarding redundant checks: the beginning of the loop has this:
> 
>                 if (pos + 2 + pos[1] > end)
>                         break;
> 
> but then individual 'case's include stuff like this:
> 
>  			if (pos > end - 3)
>  				return;
>  			if (pos[1] != 1)
> 				return;
> 
> Note that the second 'return' (validating the length, pos[1]) combined
> with the above condition (ensuring 'pos + 2 + length' doesn't exceed
> 'end'), makes the first 'return' (whose 'if' can be reworded as 'pos >
> end - pos[1] - 2') redundant. Rather than unwind the magic numbers
> there, just drop those conditions.
> 
> Fixes: 1e58252e334d ("mwifiex: Fix heap overflow in mmwifiex_process_tdls_action_frame()")
> Signed-off-by: Brian Norris <briannorris@chromium.org>

Patch applied to wireless-drivers-next.git, thanks.

70e5b8f445fd mwifiex: drop most magic numbers from mwifiex_process_tdls_action_frame()

-- 
https://patchwork.kernel.org/patch/11277011/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches