linux-kernel - Re: [PATCH] Input: ff-core - prefer struct

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Message-ID: <ZjFc--tMio1wmBpf@google.com>
Date: Tue, 30 Apr 2024 14:04:59 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Erick Archer <erick.archer@...look.com>
Cc: Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] Input: ff-core - prefer struct_size over open coded
 arithmetic

On Sat, Apr 27, 2024 at 05:05:56PM +0200, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1][2].
> 
> As the "ff" variable is a pointer to "struct ff_device" and this
> structure ends in a flexible array:
> 
> struct ff_device {
> 	[...]
> 	struct file *effect_owners[] __counted_by(max_effects);
> };
> 
> the preferred way in the kernel is to use the struct_size() helper to
> do the arithmetic instead of the calculation "size + count * size" in
> the kzalloc() function.
> 
> The struct_size() helper returns SIZE_MAX on overflow. So, refactor
> the comparison to take advantage of this.
> 
> This way, the code is more readable and safer.
> 
> This code was detected with the help of Coccinelle, and audited and
> modified manually.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Erick Archer <erick.archer@...look.com>

Applied, thank you.

-- 
Dmitry