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, 152 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/completion.h b/drivers/md/dm-vdo/completion.h
new file mode 100644
index 000000000..3407f34ce
--- /dev/null
+++ b/drivers/md/dm-vdo/completion.h
@@ -0,0 +1,152 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#ifndef VDO_COMPLETION_H
+#define VDO_COMPLETION_H
+
+#include "permassert.h"
+
+#include "status-codes.h"
+#include "types.h"
+
+/**
+ * vdo_run_completion() - Run a completion's callback or error handler on the current thread.
+ *
+ * Context: This function must be called from the correct callback thread.
+ */
+static inline void vdo_run_completion(struct vdo_completion *completion)
+{
+	if ((completion->result != VDO_SUCCESS) && (completion->error_handler != NULL)) {
+		completion->error_handler(completion);
+		return;
+	}
+
+	completion->callback(completion);
+}
+
+void vdo_set_completion_result(struct vdo_completion *completion, int result);
+
+void vdo_initialize_completion(struct vdo_completion *completion, struct vdo *vdo,
+			       enum vdo_completion_type type);
+
+/**
+ * vdo_reset_completion() - Reset a completion to a clean state, while keeping the type, vdo and
+ *                          parent information.
+ */
+static inline void vdo_reset_completion(struct vdo_completion *completion)
+{
+	completion->result = VDO_SUCCESS;
+	completion->complete = false;
+}
+
+void vdo_launch_completion_with_priority(struct vdo_completion *completion,
+					 enum vdo_completion_priority priority);
+
+/**
+ * vdo_launch_completion() - Launch a completion with default priority.
+ */
+static inline void vdo_launch_completion(struct vdo_completion *completion)
+{
+	vdo_launch_completion_with_priority(completion, VDO_WORK_Q_DEFAULT_PRIORITY);
+}
+
+/**
+ * vdo_continue_completion() - Continue processing a completion.
+ * @result: The current result (will not mask older errors).
+ *
+ * Continue processing a completion by setting the current result and calling
+ * vdo_launch_completion().
+ */
+static inline void vdo_continue_completion(struct vdo_completion *completion, int result)
+{
+	vdo_set_completion_result(completion, result);
+	vdo_launch_completion(completion);
+}
+
+void vdo_finish_completion(struct vdo_completion *completion);
+
+/**
+ * vdo_fail_completion() - Set the result of a completion if it does not already have an error,
+ *                         then finish it.
+ */
+static inline void vdo_fail_completion(struct vdo_completion *completion, int result)
+{
+	vdo_set_completion_result(completion, result);
+	vdo_finish_completion(completion);
+}
+
+/**
+ * vdo_assert_completion_type() - Assert that a completion is of the correct type.
+ *
+ * Return: VDO_SUCCESS or an error
+ */
+static inline int vdo_assert_completion_type(struct vdo_completion *completion,
+					     enum vdo_completion_type expected)
+{
+	return VDO_ASSERT(expected == completion->type,
+			  "completion type should be %u, not %u", expected,
+			  completion->type);
+}
+
+static inline void vdo_set_completion_callback(struct vdo_completion *completion,
+					       vdo_action_fn callback,
+					       thread_id_t callback_thread_id)
+{
+	completion->callback = callback;
+	completion->callback_thread_id = callback_thread_id;
+}
+
+/**
+ * vdo_launch_completion_callback() - Set the callback for a completion and launch it immediately.
+ */
+static inline void vdo_launch_completion_callback(struct vdo_completion *completion,
+						  vdo_action_fn callback,
+						  thread_id_t callback_thread_id)
+{
+	vdo_set_completion_callback(completion, callback, callback_thread_id);
+	vdo_launch_completion(completion);
+}
+
+/**
+ * vdo_prepare_completion() - Prepare a completion for launch.
+ *
+ * Resets the completion, and then sets its callback, error handler, callback thread, and parent.
+ */
+static inline void vdo_prepare_completion(struct vdo_completion *completion,
+					  vdo_action_fn callback,
+					  vdo_action_fn error_handler,
+					  thread_id_t callback_thread_id, void *parent)
+{
+	vdo_reset_completion(completion);
+	vdo_set_completion_callback(completion, callback, callback_thread_id);
+	completion->error_handler = error_handler;
+	completion->parent = parent;
+}
+
+/**
+ * vdo_prepare_completion_for_requeue() - Prepare a completion for launch ensuring that it will
+ *                                        always be requeued.
+ *
+ * Resets the completion, and then sets its callback, error handler, callback thread, and parent.
+ */
+static inline void vdo_prepare_completion_for_requeue(struct vdo_completion *completion,
+						      vdo_action_fn callback,
+						      vdo_action_fn error_handler,
+						      thread_id_t callback_thread_id,
+						      void *parent)
+{
+	vdo_prepare_completion(completion, callback, error_handler,
+			       callback_thread_id, parent);
+	completion->requeue = true;
+}
+
+void vdo_enqueue_completion(struct vdo_completion *completion,
+			    enum vdo_completion_priority priority);
+
+
+bool vdo_requeue_completion_if_needed(struct vdo_completion *completion,
+				      thread_id_t callback_thread_id);
+
+#endif /* VDO_COMPLETION_H */