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Donenfeld" To: Kees Cook Subject: Re: [PATCH v4 2/6] treewide: use prandom_u32_max() when possible Message-ID: References: <20221007180107.216067-1-Jason@zx2c4.com> <20221007180107.216067-3-Jason@zx2c4.com> <202210071241.445289C5@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <202210071241.445289C5@keescook> X-Mailman-Approved-At: Sat, 08 Oct 2022 17:03:32 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-wireless@vger.kernel.org, Ulf Hansson , x86@kernel.org, Jan Kara , Vignesh Raghavendra , linux-doc@vger.kernel.org, Peter Zijlstra , Catalin Marinas , Dave Hansen , kernel-janitors@vger.kernel.org, KP Singh , dri-devel@lists.freedesktop.org, patches@lists.linux.dev, linux-mm@kvack.org, Eric Dumazet , netdev@vger.kernel.org, linux-mtd@lists.infradead.org, kasan-dev@googlegroups.com, "H . Peter Anvin" , Andreas Noever , WANG Xuerui , Will Deacon , Christoph Hellwig , linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, Mauro Carvalho Chehab , Herbert Xu , Daniel Borkmann , Jonathan Corbet , linux-rdma@vger.kernel.org, Helge Deller , Huacai Chen , Hugh Dickins , Russell King , Jozsef Kadlecsik , Jason Gunthorpe , Dave Airlie , Paolo Abeni , "James E . J . Bottomley" , Pablo Neira Ayuso , linux-media@vger.kernel.org, Marco Elver , Yury Norov , Heiko Carstens , linux-um@lists.infradead.org, linux-mips@vger.kernel.org, linux-block@vger.kernel.org, Richard Weinberger , Borislav Petkov , linux-nvme@lists.infradead.org, loongarch@lists.linux.dev, Jakub Kicinski , Thomas Gleixner , Andy Shevchenko , Johannes Berg , linux-arm-kernel@lists.infradead.org, Jens Axboe , linux-mmc@vger.kernel.org, Thomas Bogendoerfer , Theodore Ts'o , linux-parisc@vger.kernel.org, Greg Kroah-Hartman , linux-usb@vger.kernel.org, Florian Westphal , linux-kernel@vger.kernel.org, Christoph =?utf-8?Q?B=C3=B6hmwalder?= , linux-crypto@vger.kernel.org, Jan Kara , Thomas Graf , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S . Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Oct 07, 2022 at 03:47:44PM -0700, Kees Cook wrote: > > diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c > > index 4f2f2d1bac56..56ffaa8dd3f6 100644 > > --- a/lib/test_vmalloc.c > > +++ b/lib/test_vmalloc.c > > @@ -151,9 +151,7 @@ static int random_size_alloc_test(void) > > int i; > > > > for (i = 0; i < test_loop_count; i++) { > > - n = prandom_u32(); > > - n = (n % 100) + 1; > > - > > + n = prandom_u32_max(n % 100) + 1; > > p = vmalloc(n * PAGE_SIZE); > > > > if (!p) > > This looks wrong. Cocci says: > > - n = prandom_u32(); > - n = (n % 100) + 1; > + n = prandom_u32_max(100) + 1; I agree that's wrong, but what rule did you use to make Cocci generate that? Jason