Messages in this thread | | | Date | Thu, 29 Aug 2019 09:22:28 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v9 2/3] fdt: add support for rng-seed |
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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 <keescook@chromium.org> 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
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