From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stanislaw Gruszka Subject: Re: [PATCH wireless-drivers] mt76x0: Remove VLA usage Date: Wed, 8 Aug 2018 11:24:52 +0200 Message-ID: <20180808092450.GA25772@redhat.com> References: <20180807225040.GA2164@beast> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Kalle Valo , "David S. Miller" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Kees Cook Return-path: Content-Disposition: inline In-Reply-To: <20180807225040.GA2164@beast> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Aug 07, 2018 at 03:50:40PM -0700, Kees Cook wrote: > Even with "const" variables, the compiler will generate warnings about > VLA usage. In the quest to remove all VLAs from the kernel[1], this uses > a #define instead of a const to do the array sizing. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com > > Fixes: e87b5039511a ("mt76x0: eeprom files") > Signed-off-by: Kees Cook > --- > Please include this for the v4.19 merge window. The VLA was introduced > with the new source file (which I also note is missing a SPDX line), so I thought SPDX line is needed only if file has no license and eeprom.c file and other mt76x0 files have specified the license. Is SPDX still needed in that case ? > +#define MT_MAP_READS DIV_ROUND_UP(MT_EFUSE_USAGE_MAP_SIZE, 16) > static int > mt76x0_efuse_physical_size_check(struct mt76x0_dev *dev) > { > - const int map_reads = DIV_ROUND_UP(MT_EFUSE_USAGE_MAP_SIZE, 16); > - u8 data[map_reads * 16]; Why this is variable length array? DIV_ROUND_UP can not be calculated at compile time? But if so, macro do not change the situation either. Thanks Stanislaw