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, 62 insertions, 0 deletions

diff --git a/net/openvswitch/meter.h b/net/openvswitch/meter.h
new file mode 100644
index 000000000..8bbf983cd
--- /dev/null
+++ b/net/openvswitch/meter.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2017 Nicira, Inc.
+ */
+
+#ifndef METER_H
+#define METER_H 1
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/netlink.h>
+#include <linux/openvswitch.h>
+#include <linux/skbuff.h>
+#include <linux/bits.h>
+
+#include "flow.h"
+struct datapath;
+
+#define DP_MAX_BANDS		1
+#define DP_METER_ARRAY_SIZE_MIN	BIT_ULL(10)
+#define DP_METER_NUM_MAX	(200000UL)
+
+struct dp_meter_band {
+	u32 type;
+	u32 rate;
+	u32 burst_size;
+	u64 bucket; /* 1/1000 packets, or in bits */
+	struct ovs_flow_stats stats;
+};
+
+struct dp_meter {
+	spinlock_t lock;    /* Per meter lock */
+	struct rcu_head rcu;
+	u32 id;
+	u16 kbps:1, keep_stats:1;
+	u16 n_bands;
+	u32 max_delta_t;
+	u64 used;
+	struct ovs_flow_stats stats;
+	struct dp_meter_band bands[] __counted_by(n_bands);
+};
+
+struct dp_meter_instance {
+	struct rcu_head rcu;
+	u32 n_meters;
+	struct dp_meter __rcu *dp_meters[] __counted_by(n_meters);
+};
+
+struct dp_meter_table {
+	struct dp_meter_instance __rcu *ti;
+	u32 count;
+	u32 max_meters_allowed;
+};
+
+extern struct genl_family dp_meter_genl_family;
+int ovs_meters_init(struct datapath *dp);
+void ovs_meters_exit(struct datapath *dp);
+bool ovs_meter_execute(struct datapath *dp, struct sk_buff *skb,
+		       struct sw_flow_key *key, u32 meter_id);
+
+#endif /* meter.h */