openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 102 insertions, 0 deletions

diff --git a/crypto/fips.c b/crypto/fips.c
new file mode 100644
index 000000000..c59711248
--- /dev/null
+++ b/crypto/fips.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * FIPS 200 support.
+ *
+ * Copyright (c) 2008 Neil Horman <nhorman@tuxdriver.com>
+ */
+
+#include <linux/export.h>
+#include <linux/fips.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/sysctl.h>
+#include <linux/notifier.h>
+#include <linux/string_choices.h>
+#include <generated/utsrelease.h>
+
+int fips_enabled;
+EXPORT_SYMBOL_GPL(fips_enabled);
+
+ATOMIC_NOTIFIER_HEAD(fips_fail_notif_chain);
+EXPORT_SYMBOL_GPL(fips_fail_notif_chain);
+
+/* Process kernel command-line parameter at boot time. fips=0 or fips=1 */
+static int __init fips_enable(char *str)
+{
+	if (kstrtoint(str, 0, &fips_enabled))
+		return 0;
+
+	fips_enabled = !!fips_enabled;
+	pr_info("fips mode: %s\n", str_enabled_disabled(fips_enabled));
+	return 1;
+}
+
+__setup("fips=", fips_enable);
+
+#define FIPS_MODULE_NAME CONFIG_CRYPTO_FIPS_NAME
+#ifdef CONFIG_CRYPTO_FIPS_CUSTOM_VERSION
+#define FIPS_MODULE_VERSION CONFIG_CRYPTO_FIPS_VERSION
+#else
+#define FIPS_MODULE_VERSION UTS_RELEASE
+#endif
+
+static char fips_name[] = FIPS_MODULE_NAME;
+static char fips_version[] = FIPS_MODULE_VERSION;
+
+static const struct ctl_table crypto_sysctl_table[] = {
+	{
+		.procname	= "fips_enabled",
+		.data		= &fips_enabled,
+		.maxlen		= sizeof(int),
+		.mode		= 0444,
+		.proc_handler	= proc_dointvec
+	},
+	{
+		.procname	= "fips_name",
+		.data		= &fips_name,
+		.maxlen		= 64,
+		.mode		= 0444,
+		.proc_handler	= proc_dostring
+	},
+	{
+		.procname	= "fips_version",
+		.data		= &fips_version,
+		.maxlen		= 64,
+		.mode		= 0444,
+		.proc_handler	= proc_dostring
+	},
+};
+
+static struct ctl_table_header *crypto_sysctls;
+
+static void crypto_proc_fips_init(void)
+{
+	crypto_sysctls = register_sysctl("crypto", crypto_sysctl_table);
+}
+
+static void crypto_proc_fips_exit(void)
+{
+	unregister_sysctl_table(crypto_sysctls);
+}
+
+void fips_fail_notify(void)
+{
+	if (fips_enabled)
+		atomic_notifier_call_chain(&fips_fail_notif_chain, 0, NULL);
+}
+EXPORT_SYMBOL_GPL(fips_fail_notify);
+
+static int __init fips_init(void)
+{
+	crypto_proc_fips_init();
+	return 0;
+}
+
+static void __exit fips_exit(void)
+{
+	crypto_proc_fips_exit();
+}
+
+module_init(fips_init);
+module_exit(fips_exit);