FAILED: patch "[PATCH] iommufd: Break the loop on failure in" failed to apply to 6.12-stable tree

FAILED: patch "[PATCH] iommufd: Break the loop on failure in" failed to apply to 6.12-stable tree

[gregkh]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 172fc8b19825a0f5884c38f2289188284e2d45ee
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026071611-prong-distrust-2ab3@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 172fc8b19825a0f5884c38f2289188284e2d45ee Mon Sep 17 00:00:00 2001
From: Nicolin Chen <nicolinc@nvidia.com>
Date: Mon, 1 Jun 2026 13:42:36 -0700
Subject: [PATCH] iommufd: Break the loop on failure in
 iommufd_fault_fops_read()

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>

diff --git a/drivers/iommu/iommufd/eventq.c b/drivers/iommu/iommufd/eventq.c
index 613024ca8f1f..1c010e691f97 100644
--- a/drivers/iommu/iommufd/eventq.c
+++ b/drivers/iommu/iommufd/eventq.c
@@ -168,6 +168,8 @@ static ssize_t iommufd_fault_fops_read(struct file *filep, char __user *buf,
 			}
 			done += fault_size;
 		}
+		if (rc)
+			break;
 	}
 	mutex_unlock(&fault->mutex);
 

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

[Sasha Levin]

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>
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 8226e28d79a510..4b37244003f2d7 100644
--- a/drivers/iommu/iommufd/fault.c
+++ b/drivers/iommu/iommufd/fault.c
@@ -296,6 +296,8 @@ 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