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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id t189sm4180836pfd.58.2019.08.29.09.22.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2019 09:22:29 -0700 (PDT) Date: Thu, 29 Aug 2019 09:22:28 -0700 From: Kees Cook To: Hsin-Yi Wang Subject: Re: [PATCH v9 2/3] fdt: add support for rng-seed Message-ID: <201908290921.1F0FCC9E5@keescook> References: <20190822071522.143986-1-hsinyi@chromium.org> <20190822071522.143986-3-hsinyi@chromium.org> <5d5ed368.1c69fb81.419fc.0803@mx.google.com> <201908241203.92CC0BE8@keescook> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190829_092231_179521_8112D044 X-CRM114-Status: GOOD ( 23.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kate Stewart , Peter Zijlstra , Catalin Marinas , Mukesh Ojha , Grzegorz Halat , "H . Peter Anvin" , Guenter Roeck , Will Deacon , Marek Szyprowski , Rob Herring , Daniel Thompson , Anders Roxell , Yury Norov , Marc Zyngier , Russell King , Aaro Koskinen , Ingo Molnar , Viresh Kumar , Waiman Long , "Paul E . McKenney" , Wei Li , Alexey Dobriyan , Julien Thierry , Len Brown , Arnd Bergmann , Rik van Riel , Stephen Boyd , Shaokun Zhang , Mike Rapoport , Borislav Petkov , Josh Poimboeuf , Thomas Gleixner , "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" , "Theodore Y . Ts'o" , Greg Kroah-Hartman , Marcelo Tosatti , lkml , Armijn Hemel , Jiri Kosina , Mathieu Desnoyers , Andrew Morton , Tim Chen , "David S . Miller" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Aug 29, 2019 at 06:03:57PM +0800, Hsin-Yi Wang wrote: > On Thu, Aug 29, 2019 at 1:36 AM Kees Cook wrote: > > > > Can this please be a boot param (with the default controlled by the > > CONFIG)? See how CONFIG_RANDOM_TRUST_CPU is wired up... > > > > -Kees > > > > Currently rng-seed read and added in setup_arch() --> > setup_machine_fdt().. -> early_init_dt_scan_chosen(), which is earlier > than parse_early_param() that initializes early_param. > > If we want to set it as a boot param, add_bootloader_randomness() can > only be called after parse_early_param(). The seed can't be directly > added to pool after it's read in. We need to store into global > variable and load it later. > If this seems okay then I'll add a patch for this. Thanks This seems like a good idea to me. > > --- a/drivers/of/fdt.c > +++ b/drivers/of/fdt.c > @@ -1096,13 +1096,15 @@ static const char *config_cmdline = CONFIG_CMDLINE; > > +const void* rng_seed; > +int rng_seed_len; These should be __initdata, yes? > + > int __init early_init_dt_scan_chosen(unsigned long node, const char *uname, > int depth, > void *data) > { > int l = 0; > const char *p = NULL; > char *cmdline = data; > - const void *rng_seed; > > pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname); > > @@ -1137,10 +1139,8 @@ int __init early_init_dt_scan_chosen(unsigned > long node, const char *uname, > > pr_debug("Command line is: %s\n", (char*)data); > > - rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l); > - if (rng_seed && l > 0) { > - add_bootloader_randomness(rng_seed, l); // > Originally it's added to entropy pool here > - > + rng_seed = of_get_flat_dt_prop(node, "rng-seed", &rng_seed_len); > + if (rng_seed && rng_seed_len > 0) { > /* try to clear seed so it won't be found. */ > > diff --git a/include/linux/random.h b/include/linux/random.h > index 831a002a1882..946840bba7c1 100644 > --- a/include/linux/random.h > +++ b/include/linux/random.h > @@ -31,6 +31,15 @@ static inline void add_latent_entropy(void) > static inline void add_latent_entropy(void) {} > #endif > > +extern const void* rng_seed; > +extern int rng_seed_len; > + > +static inline void add_bootloader_entropy(void) > +{ > + if (rng_seed && rng_seed_len > 0) > + add_bootloader_randomness(rng_seed, rng_seed_len); > +} And this should be __init > + > extern void add_input_randomness(unsigned int type, unsigned int code, > unsigned int value) __latent_entropy; > extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy; > diff --git a/init/main.c b/init/main.c > index 71847af32e4e..f74a8c7b34af 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -645,6 +645,7 @@ asmlinkage __visible void __init start_kernel(void) > * - adding command line entropy > */ > rand_initialize(); > + add_bootloader_entropy(); > add_latent_entropy(); > add_device_randomness(command_line, strlen(command_line)); > boot_init_stack_canary(); But yeah, looks reasonable to me. -- Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel