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, 206 insertions, 0 deletions

diff --git a/drivers/md/dm-uevent.c b/drivers/md/dm-uevent.c
new file mode 100644
index 000000000..491738263
--- /dev/null
+++ b/drivers/md/dm-uevent.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Device Mapper Uevent Support (dm-uevent)
+ *
+ * Copyright IBM Corporation, 2007
+ *	Author: Mike Anderson <andmike@linux.vnet.ibm.com>
+ */
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/kobject.h>
+#include <linux/dm-ioctl.h>
+#include <linux/export.h>
+
+#include "dm.h"
+#include "dm-uevent.h"
+
+#define DM_MSG_PREFIX "uevent"
+
+static const struct {
+	enum dm_uevent_type type;
+	enum kobject_action action;
+	char *name;
+} _dm_uevent_type_names[] = {
+	{DM_UEVENT_PATH_FAILED, KOBJ_CHANGE, "PATH_FAILED"},
+	{DM_UEVENT_PATH_REINSTATED, KOBJ_CHANGE, "PATH_REINSTATED"},
+};
+
+static struct kmem_cache *_dm_event_cache;
+
+struct dm_uevent {
+	struct mapped_device *md;
+	enum kobject_action action;
+	struct kobj_uevent_env ku_env;
+	struct list_head elist;
+	char name[DM_NAME_LEN];
+	char uuid[DM_UUID_LEN];
+};
+
+static void dm_uevent_free(struct dm_uevent *event)
+{
+	kmem_cache_free(_dm_event_cache, event);
+}
+
+static struct dm_uevent *dm_uevent_alloc(struct mapped_device *md)
+{
+	struct dm_uevent *event;
+
+	event = kmem_cache_zalloc(_dm_event_cache, GFP_ATOMIC);
+	if (!event)
+		return NULL;
+
+	INIT_LIST_HEAD(&event->elist);
+	event->md = md;
+
+	return event;
+}
+
+static struct dm_uevent *dm_build_path_uevent(struct mapped_device *md,
+					      struct dm_target *ti,
+					      enum kobject_action action,
+					      const char *dm_action,
+					      const char *path,
+					      unsigned int nr_valid_paths)
+{
+	struct dm_uevent *event;
+
+	event = dm_uevent_alloc(md);
+	if (!event) {
+		DMERR("%s: dm_uevent_alloc() failed", __func__);
+		goto err_nomem;
+	}
+
+	event->action = action;
+
+	if (add_uevent_var(&event->ku_env, "DM_TARGET=%s", ti->type->name)) {
+		DMERR("%s: add_uevent_var() for DM_TARGET failed",
+		      __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_ACTION=%s", dm_action)) {
+		DMERR("%s: add_uevent_var() for DM_ACTION failed",
+		      __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_SEQNUM=%u",
+			   dm_next_uevent_seq(md))) {
+		DMERR("%s: add_uevent_var() for DM_SEQNUM failed",
+		      __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_PATH=%s", path)) {
+		DMERR("%s: add_uevent_var() for DM_PATH failed", __func__);
+		goto err_add;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_NR_VALID_PATHS=%d",
+			   nr_valid_paths)) {
+		DMERR("%s: add_uevent_var() for DM_NR_VALID_PATHS failed",
+		      __func__);
+		goto err_add;
+	}
+
+	return event;
+
+err_add:
+	dm_uevent_free(event);
+err_nomem:
+	return ERR_PTR(-ENOMEM);
+}
+
+/**
+ * dm_send_uevents - send uevents for given list
+ *
+ * @events:	list of events to send
+ * @kobj:	kobject generating event
+ *
+ */
+void dm_send_uevents(struct list_head *events, struct kobject *kobj)
+{
+	int r;
+	struct dm_uevent *event, *next;
+
+	list_for_each_entry_safe(event, next, events, elist) {
+		list_del_init(&event->elist);
+
+		/*
+		 * When a device is being removed this copy fails and we
+		 * discard these unsent events.
+		 */
+		if (dm_copy_name_and_uuid(event->md, event->name,
+					  event->uuid)) {
+			DMINFO("%s: skipping sending uevent for lost device",
+			       __func__);
+			goto uevent_free;
+		}
+
+		if (add_uevent_var(&event->ku_env, "DM_NAME=%s", event->name)) {
+			DMERR("%s: add_uevent_var() for DM_NAME failed",
+			      __func__);
+			goto uevent_free;
+		}
+
+		if (add_uevent_var(&event->ku_env, "DM_UUID=%s", event->uuid)) {
+			DMERR("%s: add_uevent_var() for DM_UUID failed",
+			      __func__);
+			goto uevent_free;
+		}
+
+		r = kobject_uevent_env(kobj, event->action, event->ku_env.envp);
+		if (r)
+			DMERR("%s: kobject_uevent_env failed", __func__);
+uevent_free:
+		dm_uevent_free(event);
+	}
+}
+EXPORT_SYMBOL_GPL(dm_send_uevents);
+
+/**
+ * dm_path_uevent - called to create a new path event and queue it
+ *
+ * @event_type:	path event type enum
+ * @ti:			pointer to a dm_target
+ * @path:		string containing pathname
+ * @nr_valid_paths:	number of valid paths remaining
+ *
+ */
+void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
+		   const char *path, unsigned int nr_valid_paths)
+{
+	struct mapped_device *md = dm_table_get_md(ti->table);
+	struct dm_uevent *event;
+
+	if (event_type >= ARRAY_SIZE(_dm_uevent_type_names)) {
+		DMERR("%s: Invalid event_type %d", __func__, event_type);
+		return;
+	}
+
+	event = dm_build_path_uevent(md, ti,
+				     _dm_uevent_type_names[event_type].action,
+				     _dm_uevent_type_names[event_type].name,
+				     path, nr_valid_paths);
+	if (IS_ERR(event))
+		return;
+
+	dm_uevent_add(md, &event->elist);
+}
+EXPORT_SYMBOL_GPL(dm_path_uevent);
+
+int dm_uevent_init(void)
+{
+	_dm_event_cache = KMEM_CACHE(dm_uevent, 0);
+	if (!_dm_event_cache)
+		return -ENOMEM;
+
+	DMINFO("version 1.0.3");
+
+	return 0;
+}
+
+void dm_uevent_exit(void)
+{
+	kmem_cache_destroy(_dm_event_cache);
+}