FAILED: patch "[PATCH] iommufd: Reject invalid read count in" failed to apply to 6.12-stable tree

[<gregkh@linuxfoundation.org>]

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 47916a54eeb2a9e654512ee609f71bd5b29db702
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026071602-java-pointing-40af@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 47916a54eeb2a9e654512ee609f71bd5b29db702 Mon Sep 17 00:00:00 2001
From: Nicolin Chen <nicolinc@nvidia.com>
Date: Mon, 1 Jun 2026 13:42:35 -0700
Subject: [PATCH] iommufd: Reject invalid read count in
 iommufd_fault_fops_read()

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")
Link: https://patch.msgid.link/r/85c118a606fbedc5c132a1f5ec223a5ba23b92d2.1780343944.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 f55d173c59f6..613024ca8f1f 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;
 		}