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, 105 insertions, 0 deletions

diff --git a/fs/dlm/main.c b/fs/dlm/main.c
new file mode 100644
index 000000000..a44d16da7
--- /dev/null
+++ b/fs/dlm/main.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
+**  Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+#include <linux/module.h>
+
+#include "dlm_internal.h"
+#include "lockspace.h"
+#include "lock.h"
+#include "user.h"
+#include "memory.h"
+#include "config.h"
+#include "midcomms.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/dlm.h>
+
+struct workqueue_struct *dlm_wq;
+
+static int __init init_dlm(void)
+{
+	int error;
+
+	error = dlm_memory_init();
+	if (error)
+		goto out;
+
+	dlm_midcomms_init();
+
+	error = dlm_lockspace_init();
+	if (error)
+		goto out_mem;
+
+	error = dlm_config_init();
+	if (error)
+		goto out_lockspace;
+
+	dlm_register_debugfs();
+
+	error = dlm_user_init();
+	if (error)
+		goto out_debug;
+
+	error = dlm_plock_init();
+	if (error)
+		goto out_user;
+
+	dlm_wq = alloc_workqueue("dlm_wq", WQ_PERCPU, 0);
+	if (!dlm_wq) {
+		error = -ENOMEM;
+		goto out_plock;
+	}
+
+	printk("DLM installed\n");
+
+	return 0;
+
+ out_plock:
+	dlm_plock_exit();
+ out_user:
+	dlm_user_exit();
+ out_debug:
+	dlm_unregister_debugfs();
+	dlm_config_exit();
+ out_lockspace:
+	dlm_lockspace_exit();
+ out_mem:
+	dlm_midcomms_exit();
+	dlm_memory_exit();
+ out:
+	return error;
+}
+
+static void __exit exit_dlm(void)
+{
+	/* be sure every pending work e.g. freeing is done */
+	destroy_workqueue(dlm_wq);
+	dlm_plock_exit();
+	dlm_user_exit();
+	dlm_config_exit();
+	dlm_lockspace_exit();
+	dlm_midcomms_exit();
+	dlm_unregister_debugfs();
+	dlm_memory_exit();
+}
+
+module_init(init_dlm);
+module_exit(exit_dlm);
+
+MODULE_DESCRIPTION("Distributed Lock Manager");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+EXPORT_SYMBOL_GPL(dlm_new_lockspace);
+EXPORT_SYMBOL_GPL(dlm_release_lockspace);
+EXPORT_SYMBOL_GPL(dlm_lock);
+EXPORT_SYMBOL_GPL(dlm_unlock);
+