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 6ce711f2750031d12cec91384ac5cfa0a485b60a ("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>

1 files changed, 7 insertions, 6 deletions

diff --git a/lib/idr.c b/lib/idr.c
index 99ec5bc89d25..823b813f08f8 100644
--- a/lib/idr.c
+++ b/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);