[PATCH 6.12.y 2/3] iommufd: Break the loop on failure in iommufd_fault_fops_read()

[Sasha Levin <sashal@kernel.org>]

From: Nicolin Chen <nicolinc@nvidia.com>

[ Upstream commit 172fc8b19825a0f5884c38f2289188284e2d45ee ]

On a copy_to_user() failure inside the inner list_for_each_entry, only the
inner loop breaks; the outer while re-fetches the just-restored fault group
and retries the failing copy_to_user() forever, spinning the reader at 100%
CPU with fault->mutex held.

Check rc after the inner loop and break the outer while as well.

Fixes: 07838f7fd529 ("iommufd: Add iommufd fault object")
Link: https://patch.msgid.link/r/336a9b6e44fe66a24199d3be777c405c85c98622.1780343944.git.nicolinc@nvidia.com
Cc: stable@vger.kernel.org
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
[ sashal: applied to fault.c as 6.12 lacks the eventq.c split ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/iommufd/fault.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/iommufd/fault.c b/drivers/iommu/iommufd/fault.c
index 6048d8a1c8380e..ff454494191352 100644
--- a/drivers/iommu/iommufd/fault.c
+++ b/drivers/iommu/iommufd/fault.c
@@ -299,6 +299,8 @@ static ssize_t iommufd_fault_fops_read(struct file *filep, char __user *buf,
 			}
 			done += fault_size;
 		}
+		if (rc)
+			break;
 	}
 	mutex_unlock(&fault->mutex);
 
-- 
2.53.0