3 files changed, 53 insertions, 0 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 1e1d87ead55c..c3512e7e0801 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -22,6 +22,7 @@
 #include <asm/cacheflush.h>
 #include "core.h"
 #include "patch.h"
+#include "state.h"
 #include "transition.h"
 
 /*
@@ -1009,6 +1010,13 @@ int klp_enable_patch(struct klp_patch *patch)
 
 	mutex_lock(&klp_mutex);
 
+	if (!klp_is_patch_compatible(patch)) {
+		pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
+			patch->mod->name);
+		mutex_unlock(&klp_mutex);
+		return -EINVAL;
+	}
+
 	ret = klp_init_patch_early(patch);
 	if (ret) {
 		mutex_unlock(&klp_mutex);
diff --git a/kernel/livepatch/state.c b/kernel/livepatch/state.c
index 6ab15b642c0a..7ee19476de9d 100644
--- a/kernel/livepatch/state.c
+++ b/kernel/livepatch/state.c
@@ -9,6 +9,7 @@
 
 #include <linux/livepatch.h>
 #include "core.h"
+#include "state.h"
 #include "transition.h"
 
 #define klp_for_each_state(patch, state)		\
@@ -81,3 +82,38 @@ out:
 	return last_state;
 }
 EXPORT_SYMBOL_GPL(klp_get_prev_state);
+
+/* Check if the patch is able to deal with the existing system state. */
+static bool klp_is_state_compatible(struct klp_patch *patch,
+				    struct klp_state *old_state)
+{
+	struct klp_state *state;
+
+	state = klp_get_state(patch, old_state->id);
+
+	/* A cumulative livepatch must handle all already modified states. */
+	if (!state)
+		return !patch->replace;
+
+	return state->version >= old_state->version;
+}
+
+/*
+ * Check that the new livepatch will not break the existing system states.
+ * Cumulative patches must handle all already modified states.
+ * Non-cumulative patches can touch already modified states.
+ */
+bool klp_is_patch_compatible(struct klp_patch *patch)
+{
+	struct klp_patch *old_patch;
+	struct klp_state *old_state;
+
+	klp_for_each_patch(old_patch) {
+		klp_for_each_state(old_patch, old_state) {
+			if (!klp_is_state_compatible(patch, old_state))
+				return false;
+		}
+	}
+
+	return true;
+}
diff --git a/kernel/livepatch/state.h b/kernel/livepatch/state.h
new file mode 100644
index 000000000000..49d9c16e8762
--- /dev/null
+++ b/kernel/livepatch/state.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LIVEPATCH_STATE_H
+#define _LIVEPATCH_STATE_H
+
+#include <linux/livepatch.h>
+
+bool klp_is_patch_compatible(struct klp_patch *patch);
+
+#endif /* _LIVEPATCH_STATE_H */