idr: Fix handling of IDs above INT_MAX

Khalid reported that the kernel selftests are currently failing:

selftests: test_bpf.sh
========================================
test_bpf: [FAIL]
not ok 1..8 selftests:  test_bpf.sh [FAIL]

He bisected it to 6ce711f2 ("idr: Make
1-based IDRs more efficient").

The root cause is doing a signed comparison in idr_alloc_u32() instead
of an unsigned comparison.  I went looking for any similar problems and
found a couple (which would each result in the failure to warn in two
situations that aren't supposed to happen).

I knocked up a few test-cases to prove that I was right and added them
to the test-suite.
Reported-by: Khalid Aziz <khalid.aziz@oracle.com>
Tested-by: Khalid Aziz <khalid.aziz@oracle.com>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

lib/idr.c

@@ -36,8 +36,8 @@ int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
-	int base = idr->idr_base;
-	int id = *nextid;
+	unsigned int base = idr->idr_base;
+	unsigned int id = *nextid;
 
 	if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
 		return -EINVAL;
@@ -204,10 +204,11 @@ int idr_for_each(const struct idr *idr,
 
 	radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
 		int ret;
+		unsigned long id = iter.index + base;
 
-		if (WARN_ON_ONCE(iter.index > INT_MAX))
+		if (WARN_ON_ONCE(id > INT_MAX))
 			break;
-		ret = fn(iter.index + base, rcu_dereference_raw(*slot), data);
+		ret = fn(id, rcu_dereference_raw(*slot), data);
 		if (ret)
 			return ret;
 	}
@@ -230,8 +231,8 @@ void *idr_get_next(struct idr *idr, int *nextid)
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
-	int base = idr->idr_base;
-	int id = *nextid;
+	unsigned long base = idr->idr_base;
+	unsigned long id = *nextid;
 
 	id = (id < base) ? 0 : id - base;
 	slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);

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

@@ -178,6 +178,55 @@ void idr_get_next_test(int base)
 	idr_destroy(&idr);
 }
 
+int idr_u32_cb(int id, void *ptr, void *data)
+{
+	BUG_ON(id < 0);
+	BUG_ON(ptr != DUMMY_PTR);
+	return 0;
+}
+
+void idr_u32_test1(struct idr *idr, u32 handle)
+{
+	static bool warned = false;
+	u32 id = handle;
+	int sid = 0;
+	void *ptr;
+
+	BUG_ON(idr_alloc_u32(idr, DUMMY_PTR, &id, id, GFP_KERNEL));
+	BUG_ON(id != handle);
+	BUG_ON(idr_alloc_u32(idr, DUMMY_PTR, &id, id, GFP_KERNEL) != -ENOSPC);
+	BUG_ON(id != handle);
+	if (!warned && id > INT_MAX)
+		printk("vvv Ignore these warnings\n");
+	ptr = idr_get_next(idr, &sid);
+	if (id > INT_MAX) {
+		BUG_ON(ptr != NULL);
+		BUG_ON(sid != 0);
+	} else {
+		BUG_ON(ptr != DUMMY_PTR);
+		BUG_ON(sid != id);
+	}
+	idr_for_each(idr, idr_u32_cb, NULL);
+	if (!warned && id > INT_MAX) {
+		printk("^^^ Warnings over\n");
+		warned = true;
+	}
+	BUG_ON(idr_remove(idr, id) != DUMMY_PTR);
+	BUG_ON(!idr_is_empty(idr));
+}
+
+void idr_u32_test(int base)
+{
+	DEFINE_IDR(idr);
+	idr_init_base(&idr, base);
+	idr_u32_test1(&idr, 10);
+	idr_u32_test1(&idr, 0x7fffffff);
+	idr_u32_test1(&idr, 0x80000000);
+	idr_u32_test1(&idr, 0x80000001);
+	idr_u32_test1(&idr, 0xffe00000);
+	idr_u32_test1(&idr, 0xffffffff);
+}
+
 void idr_checks(void)
 {
 	unsigned long i;
@@ -248,6 +297,9 @@ void idr_checks(void)
 	idr_get_next_test(0);
 	idr_get_next_test(1);
 	idr_get_next_test(4);
+	idr_u32_test(4);
+	idr_u32_test(1);
+	idr_u32_test(0);
 }
 
 /*