[PATCH] irda: Fix lockdep annotations in hashbin_delete().

[Colin King]

From: "David S. Miller" <davem at davemloft.net>

CVE-2017-6348

A nested lock depth was added to the hasbin_delete() code but it
doesn't actually work some well and results in tons of lockdep splats.

Fix the code instead to properly drop the lock around the operation
and just keep peeking the head of the hashbin queue.

Reported-by: Dmitry Vyukov <dvyukov at google.com>
Tested-by: Dmitry Vyukov <dvyukov at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(clean cherry pick of upstream commit 4c03b862b12f980456f9de92db6d508a4999b788)
Acked-by: Colin Ian King <colin.king at canonical.com>
---
 net/irda/irqueue.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/net/irda/irqueue.c b/net/irda/irqueue.c
index acbe61c..160dc89 100644
--- a/net/irda/irqueue.c
+++ b/net/irda/irqueue.c
@@ -383,9 +383,6 @@ hashbin_t *hashbin_new(int type)
  *    for deallocating this structure if it's complex. If not the user can
  *    just supply kfree, which should take care of the job.
  */
-#ifdef CONFIG_LOCKDEP
-static int hashbin_lock_depth = 0;
-#endif
 int hashbin_delete( hashbin_t* hashbin, FREE_FUNC free_func)
 {
 	irda_queue_t* queue;
@@ -396,22 +393,27 @@ int hashbin_delete( hashbin_t* hashbin, FREE_FUNC free_func)
 	IRDA_ASSERT(hashbin->magic == HB_MAGIC, return -1;);
 
 	/* Synchronize */
-	if ( hashbin->hb_type & HB_LOCK ) {
-		spin_lock_irqsave_nested(&hashbin->hb_spinlock, flags,
-					 hashbin_lock_depth++);
-	}
+	if (hashbin->hb_type & HB_LOCK)
+		spin_lock_irqsave(&hashbin->hb_spinlock, flags);
 
 	/*
 	 *  Free the entries in the hashbin, TODO: use hashbin_clear when
 	 *  it has been shown to work
 	 */
 	for (i = 0; i < HASHBIN_SIZE; i ++ ) {
-		queue = dequeue_first((irda_queue_t**) &hashbin->hb_queue[i]);
-		while (queue ) {
-			if (free_func)
-				(*free_func)(queue);
-			queue = dequeue_first(
-				(irda_queue_t**) &hashbin->hb_queue[i]);
+		while (1) {
+			queue = dequeue_first((irda_queue_t**) &hashbin->hb_queue[i]);
+
+			if (!queue)
+				break;
+
+			if (free_func) {
+				if (hashbin->hb_type & HB_LOCK)
+					spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
+				free_func(queue);
+				if (hashbin->hb_type & HB_LOCK)
+					spin_lock_irqsave(&hashbin->hb_spinlock, flags);
+			}
 		}
 	}
 
@@ -420,12 +422,8 @@ int hashbin_delete( hashbin_t* hashbin, FREE_FUNC free_func)
 	hashbin->magic = ~HB_MAGIC;
 
 	/* Release lock */
-	if ( hashbin->hb_type & HB_LOCK) {
+	if (hashbin->hb_type & HB_LOCK)
 		spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
-#ifdef CONFIG_LOCKDEP
-		hashbin_lock_depth--;
-#endif
-	}
 
 	/*
 	 *  Free the hashbin structure
-- 
1.9.1