Merge "Set mmap_rnd_bits to maximum value." (f03e6c80) · Commits · e / os / android_system_core

init/init.cpp

+108 −5

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@
		#include <dirent.h>
		#include <errno.h>
		#include <fcntl.h>
		#include <fstream>
		#include <inttypes.h>
		#include <libgen.h>
		#include <paths.h>
		@@ -256,6 +257,112 @@ ret:
		return result;
		}

		static void security_failure() {
		LOG(ERROR) << "Security failure...";
		panic();
		}

		#define MMAP_RND_PATH "/proc/sys/vm/mmap_rnd_bits"
		#define MMAP_RND_COMPAT_PATH "/proc/sys/vm/mmap_rnd_compat_bits"

		/* __attribute__((unused)) due to lack of mips support: see mips block
		* in set_mmap_rnd_bits_action */
		static bool __attribute__((unused)) set_mmap_rnd_bits_min(int start, int min, bool compat) {
		std::string path;
		if (compat) {
		path = MMAP_RND_COMPAT_PATH;
		} else {
		path = MMAP_RND_PATH;
		}
		std::ifstream inf(path, std::fstream::in);
		if (!inf) {
		LOG(ERROR) << "Cannot open for reading: " << path;
		return false;
		}
		while (start >= min) {
		// try to write out new value
		std::string str_val = std::to_string(start);
		std::ofstream of(path, std::fstream::out);
		if (!of) {
		LOG(ERROR) << "Cannot open for writing: " << path;
		return false;
		}
		of << str_val << std::endl;
		of.close();

		// check to make sure it was recorded
		inf.seekg(0);
		std::string str_rec;
		inf >> str_rec;
		if (str_val.compare(str_rec) == 0) {
		break;
		}
		start--;
		}
		inf.close();
		if (start < min) {
		LOG(ERROR) << "Unable to set minimum required entropy " << min << " in " << path;
		return false;
		}
		return true;
		}

		/*
		* Set /proc/sys/vm/mmap_rnd_bits and potentially
		* /proc/sys/vm/mmap_rnd_compat_bits to the maximum supported values.
		* Returns -1 if unable to set these to an acceptable value.
		*
		* To support this sysctl, the following upstream commits are needed:
		*
		* d07e22597d1d mm: mmap: add new /proc tunable for mmap_base ASLR
		* e0c25d958f78 arm: mm: support ARCH_MMAP_RND_BITS
		* 8f0d3aa9de57 arm64: mm: support ARCH_MMAP_RND_BITS
		* 9e08f57d684a x86: mm: support ARCH_MMAP_RND_BITS
		* ec9ee4acd97c drivers: char: random: add get_random_long()
		* 5ef11c35ce86 mm: ASLR: use get_random_long()
		*/
		static int set_mmap_rnd_bits_action(const std::vector<std::string>& args)
		{
		int ret = -1;

		/* values are arch-dependent */
		#if defined(__aarch64__)
		/* arm64 supports 18 - 33 bits depending on pagesize and VA_SIZE */
		if (set_mmap_rnd_bits_min(33, 24, false)
		&& set_mmap_rnd_bits_min(16, 16, true)) {
		ret = 0;
		}
		#elif defined(__x86_64__)
		/* x86_64 supports 28 - 32 bits */
		if (set_mmap_rnd_bits_min(32, 32, false)
		&& set_mmap_rnd_bits_min(16, 16, true)) {
		ret = 0;
		}
		#elif defined(__arm__) \|\| defined(__i386__)
		/* check to see if we're running on 64-bit kernel */
		bool h64 = !access(MMAP_RND_COMPAT_PATH, F_OK);
		/* supported 32-bit architecture must have 16 bits set */
		if (set_mmap_rnd_bits_min(16, 16, h64)) {
		ret = 0;
		}
		#elif defined(__mips__) \|\| defined(__mips64__)
		// TODO: add mips support b/27788820
		ret = 0;
		#else
		ERROR("Unknown architecture\n");
		#endif

		#ifdef __BRILLO__
		// TODO: b/27794137
		ret = 0;
		#endif
		if (ret == -1) {
		LOG(ERROR) << "Unable to set adequate mmap entropy value!";
		security_failure();
		}
		return ret;
		}

		static int keychord_init_action(const std::vector<std::string>& args)
		{
		keychord_init();
		@@ -414,11 +521,6 @@ static int audit_callback(void data, security_class_t /cls/, char buf, size_
		return 0;
		}

		static void security_failure() {
		LOG(ERROR) << "Security failure...";
		panic();
		}

		static void selinux_initialize(bool in_kernel_domain) {
		Timer t;

		@@ -712,6 +814,7 @@ int main(int argc, char** argv) {
		am.QueueBuiltinAction(wait_for_coldboot_done_action, "wait_for_coldboot_done");
		// ... so that we can start queuing up actions that require stuff from /dev.
		am.QueueBuiltinAction(mix_hwrng_into_linux_rng_action, "mix_hwrng_into_linux_rng");
		am.QueueBuiltinAction(set_mmap_rnd_bits_action, "set_mmap_rnd_bits");
		am.QueueBuiltinAction(keychord_init_action, "keychord_init");
		am.QueueBuiltinAction(console_init_action, "console_init");