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Date: Tue, 21 Sep 2021 18:41:24 +0200 From: Takashi Iwai <tiwai@...e.de> To: Len Baker <len.baker@....com> Cc: Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>, gushengxian <gushengxian@...ong.com>, Kees Cook <keescook@...omium.org>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, alsa-devel@...a-project.org, linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] ALSA: usx2y: Prefer struct_size over open coded arithmetic 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@....com> Thanks, applied. Takashi
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