ima: annotate iint mutex to avoid lockdep false positive warnings

It is not clear that IMA should be nested at all, but as long is it
measures files both on overlayfs and on underlying fs, we need to
annotate the iint mutex to avoid lockdep false positives related to
IMA + overlayfs, same as overlayfs annotates the inode mutex.

Reported-by: syzbot+b42fe626038981fb7bfa@syzkaller.appspotmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

security/integrity/iint.c

@@ -66,9 +66,32 @@ struct integrity_iint_cache *integrity_iint_find(struct inode *inode)
 	return iint;
 }
 
-static void iint_free(struct integrity_iint_cache *iint)
+#define IMA_MAX_NESTING (FILESYSTEM_MAX_STACK_DEPTH+1)
+
+/*
+ * It is not clear that IMA should be nested at all, but as long is it measures
+ * files both on overlayfs and on underlying fs, we need to annotate the iint
+ * mutex to avoid lockdep false positives related to IMA + overlayfs.
+ * See ovl_lockdep_annotate_inode_mutex_key() for more details.
+ */
+static inline void iint_lockdep_annotate(struct integrity_iint_cache *iint,
+					 struct inode *inode)
+{
+#ifdef CONFIG_LOCKDEP
+	static struct lock_class_key iint_mutex_key[IMA_MAX_NESTING];
+
+	int depth = inode->i_sb->s_stack_depth;
+
+	if (WARN_ON_ONCE(depth < 0 || depth >= IMA_MAX_NESTING))
+		depth = 0;
+
+	lockdep_set_class(&iint->mutex, &iint_mutex_key[depth]);
+#endif
+}
+
+static void iint_init_always(struct integrity_iint_cache *iint,
+			     struct inode *inode)
 {
-	kfree(iint->ima_hash);
 	iint->ima_hash = NULL;
 	iint->version = 0;
 	iint->flags = 0UL;
@@ -80,6 +103,14 @@ static void iint_free(struct integrity_iint_cache *iint)
 	iint->ima_creds_status = INTEGRITY_UNKNOWN;
 	iint->evm_status = INTEGRITY_UNKNOWN;
 	iint->measured_pcrs = 0;
+	mutex_init(&iint->mutex);
+	iint_lockdep_annotate(iint, inode);
+}
+
+static void iint_free(struct integrity_iint_cache *iint)
+{
+	kfree(iint->ima_hash);
+	mutex_destroy(&iint->mutex);
 	kmem_cache_free(iint_cache, iint);
 }
 
@@ -104,6 +135,8 @@ struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
 	if (!iint)
 		return NULL;
 
+	iint_init_always(iint, inode);
+
 	write_lock(&integrity_iint_lock);
 
 	p = &integrity_iint_tree.rb_node;
@@ -153,25 +186,18 @@ void integrity_inode_free(struct inode *inode)
 	iint_free(iint);
 }
 
-static void init_once(void *foo)
+static void iint_init_once(void *foo)
 {
 	struct integrity_iint_cache *iint = (struct integrity_iint_cache *) foo;
 
 	memset(iint, 0, sizeof(*iint));
-	iint->ima_file_status = INTEGRITY_UNKNOWN;
-	iint->ima_mmap_status = INTEGRITY_UNKNOWN;
-	iint->ima_bprm_status = INTEGRITY_UNKNOWN;
-	iint->ima_read_status = INTEGRITY_UNKNOWN;
-	iint->ima_creds_status = INTEGRITY_UNKNOWN;
-	iint->evm_status = INTEGRITY_UNKNOWN;
-	mutex_init(&iint->mutex);
 }
 
 static int __init integrity_iintcache_init(void)
 {
 	iint_cache =
 	    kmem_cache_create("iint_cache", sizeof(struct integrity_iint_cache),
-			      0, SLAB_PANIC, init_once);
+			      0, SLAB_PANIC, iint_init_once);
 	return 0;
 }
 DEFINE_LSM(integrity) = {