linux-kernel - [PATCH 1/3] livepatch: Nullify obj->mod in klp_module

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Date:   Thu,  7 Jun 2018 11:29:47 +0200
From:   Miroslav Benes <mbenes@...e.cz>
To:     jikos@...nel.org, jpoimboe@...hat.com, jeyu@...nel.org
Cc:     pmladek@...e.com, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH 1/3] livepatch: Nullify obj->mod in klp_module_coming()'s error path

klp_module_coming() is called for every module appearing in the system.
It sets obj->mod to a patched module for klp_object obj. Unfortunately
it leaves it set even if an error happens later in the function and the
patched module is not allowed to be loaded.

klp_is_object_loaded() uses obj->mod variable and could currently give a
wrong return value. The bug is probably harmless as of now, but we're
gonna rely on klp_is_object_loaded() and correct obj->mod much more and
the bug would be visible then.

Signed-off-by: Miroslav Benes <mbenes@...e.cz>
---
 kernel/livepatch/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 3a4656fb7047..36eb5cf38766 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -1015,6 +1015,7 @@ int klp_module_coming(struct module *mod)
 	pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
 		patch->mod->name, obj->mod->name, obj->mod->name);
 	mod->klp_alive = false;
+	obj->mod = NULL;
 	klp_cleanup_module_patches_limited(mod, patch);
 	mutex_unlock(&klp_mutex);

-- 
2.17.0