ida: Free allocated bitmap in error path

[ Upstream commit a219b856a2b993da234108307be772448f22b0ce ]

If a bitmap needs to be allocated, and then by the time the thread
is scheduled to be run again all the indices which would satisfy the
allocation have been allocated then we would leak the allocation.  Almost
impossible to hit in practice, but a trivial fix.  Found by Coverity.

Fixes: f32f004cdd ("ida: Convert to XArray")
Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

lib/idr.c

@@ -470,6 +470,7 @@ alloc:
 	goto retry;
 nospc:
 	xas_unlock_irqrestore(&xas, flags);
+	kfree(alloc);
 	return -ENOSPC;
 }
 EXPORT_SYMBOL(ida_alloc_range);

tools/testing/radix-tree/idr-test.c

@@ -523,8 +523,27 @@ static void *ida_random_fn(void *arg)
 	return NULL;
 }
 
+static void *ida_leak_fn(void *arg)
+{
+	struct ida *ida = arg;
+	time_t s = time(NULL);
+	int i, ret;
+
+	rcu_register_thread();
+
+	do for (i = 0; i < 1000; i++) {
+		ret = ida_alloc_range(ida, 128, 128, GFP_KERNEL);
+		if (ret >= 0)
+			ida_free(ida, 128);
+	} while (time(NULL) < s + 2);
+
+	rcu_unregister_thread();
+	return NULL;
+}
+
 void ida_thread_tests(void)
 {
+	DEFINE_IDA(ida);
 	pthread_t threads[20];
 	int i;
 
@@ -536,6 +555,16 @@ void ida_thread_tests(void)
 
 	while (i--)
 		pthread_join(threads[i], NULL);
+
+	for (i = 0; i < ARRAY_SIZE(threads); i++)
+		if (pthread_create(&threads[i], NULL, ida_leak_fn, &ida)) {
+			perror("creating ida thread");
+			exit(1);
+		}
+
+	while (i--)
+		pthread_join(threads[i], NULL);
+	assert(ida_is_empty(&ida));
 }
 
 void ida_tests(void)