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, 76 insertions, 0 deletions

diff --git a/security/keys/sysctl.c b/security/keys/sysctl.c
new file mode 100644
index 000000000..cde08c478
--- /dev/null
+++ b/security/keys/sysctl.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Key management controls
+ *
+ * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/key.h>
+#include <linux/sysctl.h>
+#include "internal.h"
+
+static const struct ctl_table key_sysctls[] = {
+	{
+		.procname = "maxkeys",
+		.data = &key_quota_maxkeys,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_minmax,
+		.extra1 = (void *) SYSCTL_ONE,
+		.extra2 = (void *) SYSCTL_INT_MAX,
+	},
+	{
+		.procname = "maxbytes",
+		.data = &key_quota_maxbytes,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_minmax,
+		.extra1 = (void *) SYSCTL_ONE,
+		.extra2 = (void *) SYSCTL_INT_MAX,
+	},
+	{
+		.procname = "root_maxkeys",
+		.data = &key_quota_root_maxkeys,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_minmax,
+		.extra1 = (void *) SYSCTL_ONE,
+		.extra2 = (void *) SYSCTL_INT_MAX,
+	},
+	{
+		.procname = "root_maxbytes",
+		.data = &key_quota_root_maxbytes,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_minmax,
+		.extra1 = (void *) SYSCTL_ONE,
+		.extra2 = (void *) SYSCTL_INT_MAX,
+	},
+	{
+		.procname = "gc_delay",
+		.data = &key_gc_delay,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_minmax,
+		.extra1 = (void *) SYSCTL_ZERO,
+		.extra2 = (void *) SYSCTL_INT_MAX,
+	},
+#ifdef CONFIG_PERSISTENT_KEYRINGS
+	{
+		.procname = "persistent_keyring_expiry",
+		.data = &persistent_keyring_expiry,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_minmax,
+		.extra1 = (void *) SYSCTL_ZERO,
+		.extra2 = (void *) SYSCTL_INT_MAX,
+	},
+#endif
+};
+
+static int __init init_security_keys_sysctls(void)
+{
+	register_sysctl_init("kernel/keys", key_sysctls);
+	return 0;
+}
+early_initcall(init_security_keys_sysctls);