+++ /dev/null
-From c79b44779df18e44ff12f900c44285c5ae47d363 Mon Sep 17 00:00:00 2001
-From: Sasha Levin <sashal@kernel.org>
-Date: Wed, 13 Jul 2022 01:12:21 +0200
-Subject: um: seed rng using host OS rng
-
-From: Jason A. Donenfeld <Jason@zx2c4.com>
-
-[ Upstream commit 0b9ba6135d7f18b82f3d8bebb55ded725ba88e0e ]
-
-UML generally does not provide access to special CPU instructions like
-RDRAND, and execution tends to be rather deterministic, with no real
-hardware interrupts, making good randomness really very hard, if not
-all together impossible. Not only is this a security eyebrow raiser, but
-it's also quite annoying when trying to do various pieces of UML-based
-automation that takes a long time to boot, if ever.
-
-Fix this by trivially calling getrandom() in the host and using that
-seed as "bootloader randomness", which initializes the rng immediately
-at UML boot.
-
-The old behavior can be restored the same way as on any other arch, by
-way of CONFIG_TRUST_BOOTLOADER_RANDOMNESS=n or
-random.trust_bootloader=0. So seen from that perspective, this just
-makes UML act like other archs, which is positive in its own right.
-
-Additionally, wire up arch_get_random_{int,long}() in the same way, so
-that reseeds can also make use of the host RNG, controllable by
-CONFIG_TRUST_CPU_RANDOMNESS and random.trust_cpu, per usual.
-
-Cc: stable@vger.kernel.org
-Acked-by: Johannes Berg <johannes@sipsolutions.net>
-Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
-Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
-Signed-off-by: Sasha Levin <sashal@kernel.org>
----
- arch/um/include/asm/archrandom.h | 30 ++++++++++++++++++++++++++++++
- arch/um/include/shared/os.h | 7 +++++++
- arch/um/kernel/um_arch.c | 8 ++++++++
- arch/um/os-Linux/util.c | 6 ++++++
- 4 files changed, 51 insertions(+)
- create mode 100644 arch/um/include/asm/archrandom.h
-
-diff --git a/arch/um/include/asm/archrandom.h b/arch/um/include/asm/archrandom.h
-new file mode 100644
-index 000000000000..2f24cb96391d
---- /dev/null
-+++ b/arch/um/include/asm/archrandom.h
-@@ -0,0 +1,30 @@
-+/* SPDX-License-Identifier: GPL-2.0 */
-+#ifndef __ASM_UM_ARCHRANDOM_H__
-+#define __ASM_UM_ARCHRANDOM_H__
-+
-+#include <linux/types.h>
-+
-+/* This is from <os.h>, but better not to #include that in a global header here. */
-+ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);
-+
-+static inline bool __must_check arch_get_random_long(unsigned long *v)
-+{
-+ return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
-+}
-+
-+static inline bool __must_check arch_get_random_int(unsigned int *v)
-+{
-+ return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
-+}
-+
-+static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
-+{
-+ return false;
-+}
-+
-+static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
-+{
-+ return false;
-+}
-+
-+#endif
-diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
-index 2f31d44d892e..a339938b85a0 100644
---- a/arch/um/include/shared/os.h
-+++ b/arch/um/include/shared/os.h
-@@ -12,6 +12,12 @@
- #include <irq_user.h>
- #include <longjmp.h>
- #include <mm_id.h>
-+/* This is to get size_t */
-+#ifndef __UM_HOST__
-+#include <linux/types.h>
-+#else
-+#include <sys/types.h>
-+#endif
-
- #define CATCH_EINTR(expr) while ((errno = 0, ((expr) < 0)) && (errno == EINTR))
-
-@@ -248,6 +254,7 @@ extern void stack_protections(unsigned long address);
- extern int raw(int fd);
- extern void setup_machinename(char *machine_out);
- extern void setup_hostinfo(char *buf, int len);
-+extern ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);
- extern void os_dump_core(void) __attribute__ ((noreturn));
- extern void um_early_printk(const char *s, unsigned int n);
- extern void os_fix_helper_signals(void);
-diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
-index 52e2e2a3e4ae..ecef61f9aadf 100644
---- a/arch/um/kernel/um_arch.c
-+++ b/arch/um/kernel/um_arch.c
-@@ -14,6 +14,7 @@
- #include <linux/sched/task.h>
- #include <linux/kmsg_dump.h>
- #include <linux/suspend.h>
-+#include <linux/random.h>
-
- #include <asm/processor.h>
- #include <asm/sections.h>
-@@ -342,6 +343,8 @@ int __init __weak read_initrd(void)
-
- void __init setup_arch(char **cmdline_p)
- {
-+ u8 rng_seed[32];
-+
- stack_protections((unsigned long) &init_thread_info);
- setup_physmem(uml_physmem, uml_reserved, physmem_size, highmem);
- mem_total_pages(physmem_size, iomem_size, highmem);
-@@ -351,6 +354,11 @@ void __init setup_arch(char **cmdline_p)
- strlcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
- *cmdline_p = command_line;
- setup_hostinfo(host_info, sizeof host_info);
-+
-+ if (os_getrandom(rng_seed, sizeof(rng_seed), 0) == sizeof(rng_seed)) {
-+ add_bootloader_randomness(rng_seed, sizeof(rng_seed));
-+ memzero_explicit(rng_seed, sizeof(rng_seed));
-+ }
- }
-
- void __init check_bugs(void)
-diff --git a/arch/um/os-Linux/util.c b/arch/um/os-Linux/util.c
-index 07327425d06e..fab664203f30 100644
---- a/arch/um/os-Linux/util.c
-+++ b/arch/um/os-Linux/util.c
-@@ -13,6 +13,7 @@
- #include <sys/wait.h>
- #include <sys/mman.h>
- #include <sys/utsname.h>
-+#include <sys/random.h>
- #include <init.h>
- #include <os.h>
-
-@@ -95,6 +96,11 @@ static inline void __attribute__ ((noreturn)) uml_abort(void)
- exit(127);
- }
-
-+ssize_t os_getrandom(void *buf, size_t len, unsigned int flags)
-+{
-+ return getrandom(buf, len, flags);
-+}
-+
- /*
- * UML helper threads must not handle SIGWINCH/INT/TERM
- */
---
-2.35.1
-
projects / thirdparty / kernel / stable-queue.git / commitdiff
