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, 51 insertions, 0 deletions

diff --git a/include/net/fib_notifier.h b/include/net/fib_notifier.h
new file mode 100644
index 000000000..48aad6128
--- /dev/null
+++ b/include/net/fib_notifier.h
@@ -0,0 +1,51 @@
+#ifndef __NET_FIB_NOTIFIER_H
+#define __NET_FIB_NOTIFIER_H
+
+#include <linux/types.h>
+#include <linux/notifier.h>
+#include <net/net_namespace.h>
+
+struct module;
+
+struct fib_notifier_info {
+	int family;
+	struct netlink_ext_ack  *extack;
+};
+
+enum fib_event_type {
+	FIB_EVENT_ENTRY_REPLACE,
+	FIB_EVENT_ENTRY_APPEND,
+	FIB_EVENT_ENTRY_ADD,
+	FIB_EVENT_ENTRY_DEL,
+	FIB_EVENT_RULE_ADD,
+	FIB_EVENT_RULE_DEL,
+	FIB_EVENT_NH_ADD,
+	FIB_EVENT_NH_DEL,
+	FIB_EVENT_VIF_ADD,
+	FIB_EVENT_VIF_DEL,
+};
+
+struct fib_notifier_ops {
+	int family;
+	struct list_head list;
+	unsigned int (*fib_seq_read)(const struct net *net);
+	int (*fib_dump)(struct net *net, struct notifier_block *nb,
+			struct netlink_ext_ack *extack);
+	struct module *owner;
+	struct rcu_head rcu;
+};
+
+int call_fib_notifier(struct notifier_block *nb,
+		      enum fib_event_type event_type,
+		      struct fib_notifier_info *info);
+int call_fib_notifiers(struct net *net, enum fib_event_type event_type,
+		       struct fib_notifier_info *info);
+int register_fib_notifier(struct net *net, struct notifier_block *nb,
+			  void (*cb)(struct notifier_block *nb),
+			  struct netlink_ext_ack *extack);
+int unregister_fib_notifier(struct net *net, struct notifier_block *nb);
+struct fib_notifier_ops *
+fib_notifier_ops_register(const struct fib_notifier_ops *tmpl, struct net *net);
+void fib_notifier_ops_unregister(struct fib_notifier_ops *ops);
+
+#endif