linux-kernel - [PATCH v1 05/19] livepatch: Remove "data" from struct klp

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Message-ID: <20250115082431.5550-6-pmladek@suse.com>
Date: Wed, 15 Jan 2025 09:24:17 +0100
From: Petr Mladek <pmladek@...e.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>
Cc: Joe Lawrence <joe.lawrence@...hat.com>,
	Nicolai Stange <nstange@...e.de>,
	live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>
Subject: [PATCH v1 05/19] livepatch: Remove "data" from struct klp_state

The "data" pointer in "struct klp_state" is associated with the lifetime of
the livepatch module, not the livepatch state. This means it's lost when a
livepatch is replaced, even if the new livepatch supports the same state.

Shadow variables provide a more reliable way to attach data to a livepatch
state. Their lifetime can be tied to the state's lifetime by:

- Sharing the same "id"
- Setting "is_shadow" in "struct klp_state"

Removing the "data" pointer prevents potential issues once per-object
callbacks are removed, as it cannot be used securely in that context.

Signed-off-by: Petr Mladek <pmladek@...e.com>
---
 include/linux/livepatch.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 56e71d488e71..d02d7a616338 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -175,14 +175,12 @@ struct klp_state_callbacks {
  * @block_disable: the state disablement is not supported
  * @is_shadow:	the state handles lifetime of a shadow variable with
  *		the same @id
- * @data:	custom data
  */
 struct klp_state {
 	unsigned long id;
 	struct klp_state_callbacks callbacks;
 	bool block_disable;
 	bool is_shadow;
-	void *data;
 };
 
 /**
-- 
2.47.1