[PATCH] selftests: kvm: Fix transposed calloc() arguments in the uffd helper

From: Chaithanya Lagisetty

Date: Fri Sep 04 2026 - 01:23:21 EST


uffd_setup_demand_paging() passes the element size as the first argument
to calloc() and the element count as the second:

uffd_desc->pipefds = calloc(sizeof(int), num_readers);

calloc() expects the number of elements first and the size of each element
second. The product, and therefore the allocation size, is the same either
way, so this is not a functional change, but the arguments are misleading
and GCC 14 diagnoses them with -Wcalloc-transposed-args, which is enabled
by -Wextra.

Swap the arguments to match the calloc() prototype.

Signed-off-by: Chaithanya Lagisetty <nagachaithanya9911@xxxxxxxxx>
---
tools/testing/selftests/kvm/lib/userfaultfd_util.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/userfaultfd_util.c b/tools/testing/selftests/kvm/lib/userfaultfd_util.c
index f7ce5a6ddcc2..49eff05b7d39 100644
--- a/tools/testing/selftests/kvm/lib/userfaultfd_util.c
+++ b/tools/testing/selftests/kvm/lib/userfaultfd_util.c
@@ -119,13 +119,13 @@ struct uffd_desc *uffd_setup_demand_paging(int uffd_mode, useconds_t delay,
uffd_desc = malloc(sizeof(struct uffd_desc));
TEST_ASSERT(uffd_desc, "Failed to malloc uffd descriptor");

- uffd_desc->pipefds = calloc(sizeof(int), num_readers);
+ uffd_desc->pipefds = calloc(num_readers, sizeof(int));
TEST_ASSERT(uffd_desc->pipefds, "Failed to alloc pipes");

- uffd_desc->readers = calloc(sizeof(pthread_t), num_readers);
+ uffd_desc->readers = calloc(num_readers, sizeof(pthread_t));
TEST_ASSERT(uffd_desc->readers, "Failed to alloc reader threads");

- uffd_desc->reader_args = calloc(sizeof(struct uffd_reader_args), num_readers);
+ uffd_desc->reader_args = calloc(num_readers, sizeof(struct uffd_reader_args));
TEST_ASSERT(uffd_desc->reader_args, "Failed to alloc reader_args");

uffd_desc->num_readers = num_readers;
--
2.43.0