[PATCH v1 4/7] iommufd: Reject invalid read count in iommufd_fault_fops_read()

[Nicolin Chen]

The read count must be large enough to hold one fault or a group's faults.

iommufd_fault_fops_read() does not validate the count, but returns 0 as if
the read had succeeded while leaving the pending fault in the queue.

Return -EINVAL in the undersize cases.

Fixes: 07838f7fd529 ("iommufd: Add iommufd fault object")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
 drivers/iommu/iommufd/eventq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/iommufd/eventq.c b/drivers/iommu/iommufd/eventq.c
index f55d173c59f61..613024ca8f1ff 100644
--- a/drivers/iommu/iommufd/eventq.c
+++ b/drivers/iommu/iommufd/eventq.c
@@ -142,6 +142,9 @@ static ssize_t iommufd_fault_fops_read(struct file *filep, char __user *buf,
 		if (done >= count ||
 		    group->fault_count * fault_size > count - done) {
 			iommufd_fault_deliver_restore(fault, group);
+			/* Read count doesn't fit the first fault group */
+			if (done == 0)
+				rc = -EINVAL;
 			break;
 		}
 
-- 
2.43.0