[RFC PATCH 14/21] plist: Use CHECK_DATA_CORRUPTION instead of explicit {BUG,WARN}_ON()

[Will Deacon]

CHECK_DATA_CORRUPTION() allows detected data corruption to result
consistently in either a BUG() or a WARN() depending on
CONFIG_BUG_ON_DATA_CORRUPTION.

Use CHECK_DATA_CORRUPTION() to report plist integrity checking failures,
rather than explicit use of BUG_ON() and WARN_ON().

Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
 lib/plist.c | 63 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 40 insertions(+), 23 deletions(-)

diff --git a/lib/plist.c b/lib/plist.c
index c06e98e78259..eb127eaab235 100644
--- a/lib/plist.c
+++ b/lib/plist.c
@@ -29,39 +29,46 @@
 
 static struct plist_head test_head;
 
-static void plist_check_prev_next(struct list_head *t, struct list_head *p,
-				  struct list_head *n)
+static bool plist_prev_next_invalid(struct list_head *t, struct list_head *p,
+				    struct list_head *n)
 {
-	WARN(n->prev != p || p->next != n,
-			"top: %p, n: %p, p: %p\n"
-			"prev: %p, n: %p, p: %p\n"
-			"next: %p, n: %p, p: %p\n",
+	return CHECK_DATA_CORRUPTION(n->prev != p || p->next != n,
+			"plist corruption:\n"
+			"\ttop: %p, n: %p, p: %p\n"
+			"\tprev: %p, n: %p, p: %p\n"
+			"\tnext: %p, n: %p, p: %p\n",
 			 t, t->next, t->prev,
 			p, p->next, p->prev,
 			n, n->next, n->prev);
 }
 
-static void plist_check_list(struct list_head *top)
+static bool plist_list_invalid(struct list_head *top)
 {
 	struct list_head *prev = top, *next = top->next;
+	bool corruption;
 
-	plist_check_prev_next(top, prev, next);
+	corruption = plist_prev_next_invalid(top, prev, next);
 	while (next != top) {
 		prev = next;
 		next = prev->next;
-		plist_check_prev_next(top, prev, next);
+		corruption |= plist_prev_next_invalid(top, prev, next);
 	}
+
+	return corruption;
 }
 
-static void plist_check_head(struct plist_head *head)
+static bool plist_head_valid(struct plist_head *head)
 {
+	bool corruption = false;
+
 	if (!plist_head_empty(head))
-		plist_check_list(&plist_first(head)->prio_list);
-	plist_check_list(&head->node_list);
+		corruption |= plist_list_invalid(&plist_first(head)->prio_list);
+	corruption |= plist_list_invalid(&head->node_list);
+	return !corruption;
 }
 
 #else
-# define plist_check_head(h)	do { } while (0)
+# define plist_head_valid(h)	(true)
 #endif
 
 /**
@@ -75,9 +82,12 @@ void plist_add(struct plist_node *node, struct plist_head *head)
 	struct plist_node *first, *iter, *prev = NULL;
 	struct list_head *node_next = &head->node_list;
 
-	plist_check_head(head);
-	WARN_ON(!plist_node_empty(node));
-	WARN_ON(!list_empty(&node->prio_list));
+	if (!plist_head_valid(head) ||
+	    CHECK_DATA_CORRUPTION(!plist_node_empty(node),
+			"plist_add corruption. node list is not empty.\n") ||
+	    CHECK_DATA_CORRUPTION(!list_empty(&node->prio_list),
+			"plist_add corruption. node prio list is not empty.\n"))
+		return;
 
 	if (plist_head_empty(head))
 		goto ins_node;
@@ -100,7 +110,8 @@ void plist_add(struct plist_node *node, struct plist_head *head)
 ins_node:
 	list_add_tail(&node->node_list, node_next);
 
-	plist_check_head(head);
+	if (!plist_head_valid(head))
+		return;
 }
 
 /**
@@ -111,7 +122,8 @@ void plist_add(struct plist_node *node, struct plist_head *head)
  */
 void plist_del(struct plist_node *node, struct plist_head *head)
 {
-	plist_check_head(head);
+	if (!plist_head_valid(head))
+		return;
 
 	if (!list_empty(&node->prio_list)) {
 		if (node->node_list.next != &head->node_list) {
@@ -129,7 +141,8 @@ void plist_del(struct plist_node *node, struct plist_head *head)
 
 	list_del_init(&node->node_list);
 
-	plist_check_head(head);
+	if (!plist_head_valid(head))
+		return;
 }
 
 /**
@@ -147,9 +160,12 @@ void plist_requeue(struct plist_node *node, struct plist_head *head)
 	struct plist_node *iter;
 	struct list_head *node_next = &head->node_list;
 
-	plist_check_head(head);
-	BUG_ON(plist_head_empty(head));
-	BUG_ON(plist_node_empty(node));
+	if (!plist_head_valid(head) ||
+	    CHECK_DATA_CORRUPTION(plist_head_empty(head),
+			"plist_requeue corruption. head list is empty.\n") ||
+	    CHECK_DATA_CORRUPTION(plist_node_empty(node),
+			"plist_requeue corruption. node list is empty.\n"))
+		return;
 
 	if (node == plist_last(head))
 		return;
@@ -169,7 +185,8 @@ void plist_requeue(struct plist_node *node, struct plist_head *head)
 	}
 	list_add_tail(&node->node_list, node_next);
 
-	plist_check_head(head);
+	if (!plist_head_valid(head))
+		return;
 }
 
 #ifdef CONFIG_CHECK_INTEGRITY_PLIST
-- 
2.20.1