Commit a1994480 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'hardening-v5.18-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux 

Pull hardening fixes from Kees Cook:

 - latent_entropy: Use /dev/urandom instead of small GCC seed (Jason
   Donenfeld)

 - uapi/stddef.h: add missed include guards (Tadeusz Struk)

* tag 'hardening-v5.18-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: latent_entropy: use /dev/urandom
  uapi/linux/stddef.h: Add include guards
parents c1488c97 c40160f2

include/uapi/linux/stddef.h

+4 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

#ifndef _UAPI_LINUX_STDDEF_H

#define _UAPI_LINUX_STDDEF_H



#include <linux/compiler_types.h>



#ifndef __always_inline
@@ -41,3 +44,4 @@ 
		struct { } __empty_ ## NAME; \

		TYPE NAME[]; \

	}

#endif

scripts/gcc-plugins/latent_entropy_plugin.c

+27 −17
Original line number Diff line number Diff line
@@ -86,25 +86,31 @@ static struct plugin_info latent_entropy_plugin_info = { 
	.help		= "disable\tturn off latent entropy instrumentation\n",

};



static unsigned HOST_WIDE_INT seed;

/*

 * get_random_seed() (this is a GCC function) generates the seed.

 * This is a simple random generator without any cryptographic security because

 * the entropy doesn't come from here.

 */

static unsigned HOST_WIDE_INT deterministic_seed;

static unsigned HOST_WIDE_INT rnd_buf[32];

static size_t rnd_idx = ARRAY_SIZE(rnd_buf);

static int urandom_fd = -1;



static unsigned HOST_WIDE_INT get_random_const(void)

{

	unsigned int i;

	unsigned HOST_WIDE_INT ret = 0;



	for (i = 0; i < 8 * sizeof(ret); i++) {

		ret = (ret << 1) | (seed & 1);

		seed >>= 1;

		if (ret & 1)

			seed ^= 0xD800000000000000ULL;

	if (deterministic_seed) {

		unsigned HOST_WIDE_INT w = deterministic_seed;

		w ^= w << 13;

		w ^= w >> 7;

		w ^= w << 17;

		deterministic_seed = w;

		return deterministic_seed;

	}



	return ret;

	if (urandom_fd < 0) {

		urandom_fd = open("/dev/urandom", O_RDONLY);

		gcc_assert(urandom_fd >= 0);

	}

	if (rnd_idx >= ARRAY_SIZE(rnd_buf)) {

		gcc_assert(read(urandom_fd, rnd_buf, sizeof(rnd_buf)) == sizeof(rnd_buf));

		rnd_idx = 0;

	}

	return rnd_buf[rnd_idx++];

}



static tree tree_get_random_const(tree type)
@@ -537,8 +543,6 @@ static void latent_entropy_start_unit(void *gcc_data __unused, 
	tree type, id;

	int quals;



	seed = get_random_seed(false);



	if (in_lto_p)

		return;
@@ -573,6 +577,12 @@ __visible int plugin_init(struct plugin_name_args *plugin_info, 
	const struct plugin_argument * const argv = plugin_info->argv;

	int i;



	/*

	 * Call get_random_seed() with noinit=true, so that this returns

	 * 0 in the case where no seed has been passed via -frandom-seed.

	 */

	deterministic_seed = get_random_seed(true);



	static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {

		{

			.base = &latent_entropy_decl,