livepatch: robustify klp_register_patch() API error checking

Jiri Kosina · Jiri Kosina · commit 61bf12d3304d · 2016-04-07T20:42:38.000+02:00
Commit 425595a ("livepatch: reuse module loader code to write relocations") adds a possibility of dereferncing pointers supplied by the consumer of the livepatch API before sanity (NULL) checking them (patch and patch->mod). Spotted by smatch tool. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Jessica Yu <jeyu@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
@@ -876,6 +876,9 @@ int klp_register_patch(struct klp_patch *patch)
 {
 	int ret;
 
+	if (!patch || !patch->mod)
+		return -EINVAL;
+
 	if (!is_livepatch_module(patch->mod)) {
 		pr_err("module %s is not marked as a livepatch module",
 		       patch->mod->name);
@@ -885,9 +888,6 @@ int klp_register_patch(struct klp_patch *patch)
 	if (!klp_initialized())
 		return -ENODEV;
 
-	if (!patch || !patch->mod)
-		return -EINVAL;
-
 	/*
 	 * A reference is taken on the patch module to prevent it from being
 	 * unloaded.  Right now, we don't allow patch modules to unload since
