[PATCH 6.12 066/567] iommufd/selftest: Check for overflow in IOMMU_TEST_OP_ADD_RESERVED

Greg Kroah-Hartman
2026-01-06T17:20:14Z

From: Jason Gunthorpe <jgg@nvidia.com>

[ Upstream commit e6a973af11135439de32ece3b9cbe3bfc043bea8 ]

syzkaller found it could overflow math in the test infrastructure and
cause a WARN_ON by corrupting the reserved interval tree. This only
effects test kernels with CONFIG_IOMMUFD_TEST.

Validate the user input length in the test ioctl.

Fixes: f4b20bb34c83 ("iommufd: Add kernel support for testing iommufd")
Link: https://patch.msgid.link/r/0-v1-cd99f6049ba5+51-iommufd_syz_add_resv_jgg@nvidia.com
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Yi Liu <yi.l.liu@intel.com>
Reported-by: syzbot+57fdb0cf6a0c5d1f15a2@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69368129.a70a0220.38f243.008f.GAE@google.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iommu/iommufd/selftest.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index 540437be168a0..aed260d4a93cc 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -836,14 +836,20 @@ static int iommufd_test_add_reserved(struct iommufd_ucmd *ucmd,
unsigned int mockpt_id,
unsigned long start, size_t length)
{
+ unsigned long last;
struct iommufd_ioas *ioas;
int rc;

+ if (!length)
+ return -EINVAL;
+ if (check_add_overflow(start, length - 1, &last))
+ return -EOVERFLOW;
+
ioas = iommufd_get_ioas(ucmd->ictx, mockpt_id);
if (IS_ERR(ioas))
return PTR_ERR(ioas);
down_write(&ioas->iopt.iova_rwsem);
- rc = iopt_reserve_iova(&ioas->iopt, start, start + length - 1, NULL);
+ rc = iopt_reserve_iova(&ioas->iopt, start, last, NULL);
up_write(&ioas->iopt.iova_rwsem);
iommufd_put_object(ucmd->ictx, &ioas->obj);
return rc;
--
2.51.0