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, 54 insertions, 0 deletions

diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
new file mode 100644
index 000000000..dec7522b6
--- /dev/null
+++ b/include/net/netprio_cgroup.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * netprio_cgroup.h			Control Group Priority set
+ *
+ * Authors:	Neil Horman <nhorman@tuxdriver.com>
+ */
+
+#ifndef _NETPRIO_CGROUP_H
+#define _NETPRIO_CGROUP_H
+
+#include <linux/cgroup.h>
+#include <linux/hardirq.h>
+#include <linux/rcupdate.h>
+
+#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
+struct netprio_map {
+	struct rcu_head rcu;
+	u32 priomap_len;
+	u32 priomap[];
+};
+
+static inline u32 task_netprioidx(struct task_struct *p)
+{
+	struct cgroup_subsys_state *css;
+	u32 idx;
+
+	rcu_read_lock();
+	css = task_css(p, net_prio_cgrp_id);
+	idx = css->id;
+	rcu_read_unlock();
+	return idx;
+}
+
+static inline void sock_update_netprioidx(struct sock_cgroup_data *skcd)
+{
+	if (in_interrupt())
+		return;
+
+	sock_cgroup_set_prioidx(skcd, task_netprioidx(current));
+}
+
+#else /* !CONFIG_CGROUP_NET_PRIO */
+
+static inline u32 task_netprioidx(struct task_struct *p)
+{
+	return 0;
+}
+
+static inline void sock_update_netprioidx(struct sock_cgroup_data *skcd)
+{
+}
+
+#endif /* CONFIG_CGROUP_NET_PRIO */
+#endif  /* _NET_CLS_CGROUP_H */