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authorPetr Mladek <pmladek@suse.com>2019-10-30 16:43:11 +0100
committerPetr Mladek <pmladek@suse.com>2019-11-01 13:08:19 +0100
commit92c9abf5e57500ea7dc59a55273aa7850b631bda (patch)
treeb46d995199bb62760ccb243f15ef1c7c15949b53
parent73727f4dafa2df107e85753c5ab703a1f344e1f1 (diff)
livepatch: Allow to distinguish different version of system state changes
The atomic replace runs pre/post (un)install callbacks only from the new livepatch. There are several reasons for this: + Simplicity: clear ordering of operations, no interactions between old and new callbacks. + Reliability: only new livepatch knows what changes can already be made by older livepatches and how to take over the state. + Testing: the atomic replace can be properly tested only when a newer livepatch is available. It might be too late to fix unwanted effect of callbacks from older livepatches. It might happen that an older change is not enough and the same system state has to be modified another way. Different changes need to get distinguished by a version number added to struct klp_state. The version can also be used to prevent loading incompatible livepatches. The check is done when the livepatch is enabled. The rules are: + Any completely new system state modification is allowed. + System state modifications with the same or higher version are allowed for already modified system states. + Cumulative livepatches must handle all system state modifications from already installed livepatches. + Non-cumulative livepatches are allowed to touch already modified system states. Link: http://lkml.kernel.org/r/20191030154313.13263-4-pmladek@suse.com To: Jiri Kosina <jikos@kernel.org> Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Cc: Nicolai Stange <nstange@suse.de> Cc: live-patching@vger.kernel.org Cc: linux-kernel@vger.kernel.org Acked-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Joe Lawrence <joe.lawrence@redhat.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
-rw-r--r--include/linux/livepatch.h2
-rw-r--r--kernel/livepatch/core.c8
-rw-r--r--kernel/livepatch/state.c36
-rw-r--r--kernel/livepatch/state.h9
4 files changed, 55 insertions, 0 deletions
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 726947338fd5..e894e74905f3 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -133,10 +133,12 @@ struct klp_object {
/**
* struct klp_state - state of the system modified by the livepatch
* @id: system state identifier (non-zero)
+ * @version: version of the change
* @data: custom data
*/
struct klp_state {
unsigned long id;
+ unsigned int version;
void *data;
};
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 */