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, 64 insertions, 0 deletions

diff --git a/net/sunrpc/xprtrdma/module.c b/net/sunrpc/xprtrdma/module.c
new file mode 100644
index 000000000..697f571d4
--- /dev/null
+++ b/net/sunrpc/xprtrdma/module.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+/*
+ * Copyright (c) 2015, 2017 Oracle.  All rights reserved.
+ */
+
+/* rpcrdma.ko module initialization
+ */
+
+#include <linux/types.h>
+#include <linux/compiler.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sunrpc/svc_rdma.h>
+#include <linux/sunrpc/rdma_rn.h>
+
+#include <asm/swab.h>
+
+#include "xprt_rdma.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/rpcrdma.h>
+
+MODULE_AUTHOR("Open Grid Computing and Network Appliance, Inc.");
+MODULE_DESCRIPTION("RPC/RDMA Transport");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("svcrdma");
+MODULE_ALIAS("xprtrdma");
+MODULE_ALIAS("rpcrdma6");
+
+static void __exit rpc_rdma_cleanup(void)
+{
+	xprt_rdma_cleanup();
+	svc_rdma_cleanup();
+	rpcrdma_ib_client_unregister();
+}
+
+static int __init rpc_rdma_init(void)
+{
+	int rc;
+
+	rc = rpcrdma_ib_client_register();
+	if (rc)
+		goto out_rc;
+
+	rc = svc_rdma_init();
+	if (rc)
+		goto out_ib_client;
+
+	rc = xprt_rdma_init();
+	if (rc)
+		goto out_svc_rdma;
+
+	return 0;
+
+out_svc_rdma:
+	svc_rdma_cleanup();
+out_ib_client:
+	rpcrdma_ib_client_unregister();
+out_rc:
+	return rc;
+}
+
+module_init(rpc_rdma_init);
+module_exit(rpc_rdma_cleanup);