Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 21 Sep 2021 18:41:24 +0200
Message-ID: <s5h35px98zv.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Len Baker <len.baker@gmx.com>
Cc:     Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
        gushengxian <gushengxian@yulong.com>,
        Kees Cook <keescook@chromium.org>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        alsa-devel@alsa-project.org, linux-hardening@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ALSA: usx2y: Prefer struct_size over open coded arithmetic
In-Reply-To: <20210919133727.44694-1-len.baker@gmx.com>
References: <20210919133727.44694-1-len.baker@gmx.com>
User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka)
 FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3
 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Sun, 19 Sep 2021 15:37:27 +0200,
Len Baker wrote:
> 
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
> 
> In this case this is not actually dynamic size: all the operands
> involved in the calculation are constant values. However it is better to
> refactor this anyway, just to keep the open-coded math idiom out of
> code.
> 
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + size * count" in the kzalloc() function.
> 
> Also, take the opportunity to refactor the declaration variables to make
> it more easy to read.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> 
> Signed-off-by: Len Baker <len.baker@gmx.com>

Thanks, applied.


Takashi