FAILED: patch "[PATCH] media: ipu-bridge: Fix use-after-free in IVSC error path" failed to apply to 6.6-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.6-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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 3d42d1c82717f0853379b516a7fab54b636e09cc
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110433-duct-chirping-3042@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 3d42d1c82717f0853379b516a7fab54b636e09cc Mon Sep 17 00:00:00 2001
From: Yibo Tan <lhfff@tju.edu.cn>
Date: Mon, 7 Sep 2026 06:43:50 +0800
Subject: [PATCH] media: ipu-bridge: Fix use-after-free in IVSC error path

ipu_bridge_get_ivsc_acpi_dev() returns an ACPI device with a reference
held. If no matching CSI device is found, ipu_bridge_check_ivsc_dev()
drops that reference before passing the device to dev_err(). Concurrent
CSI device and ACPI namespace removal can drop the other references,
making this the final put. dev_err() then reads the freed struct
acpi_device and its kobject name.

This was reproduced without kprobes by racing normal CSI platform-device
unregistration and ACPI configfs table removal against the production
ipu_bridge_init() entry. KASAN reported the final free through
device_release(), followed by invalid reads through _dev_err().

Emit the error message while the lookup reference is still held, then
drop the reference as before.

Source reproducers and vulnerable/fixed serial logs, with only the build
hostname redacted, are available at:
https://github.com/kimaiden1984-boop/linux-ipu-bridge-acpi-uaf-reproducer

The fixed target builds with W=1 on x86-64. This was not tested on
physical IPU hardware. The tests establish runtime reachability but do
not measure occurrence frequency on shipping systems or establish
exploitability.

Fixes: c66821f381ae ("media: pci: intel: Add IVSC support for IPU bridge driver")
Cc: stable@vger.kernel.org
Assisted-by: Codex:GPT-5
Signed-off-by: Yibo Tan <lhfff@tju.edu.cn>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

diff --git a/drivers/media/pci/intel/ipu-bridge.c b/drivers/media/pci/intel/ipu-bridge.c
index 0817216f72ea..63470be888ba 100644
--- a/drivers/media/pci/intel/ipu-bridge.c
+++ b/drivers/media/pci/intel/ipu-bridge.c
@@ -351,8 +351,8 @@ static int ipu_bridge_check_ivsc_dev(struct ipu_sensor *sensor,
 	if (adev) {
 		csi_dev = ipu_bridge_get_ivsc_csi_dev(adev);
 		if (!csi_dev) {
-			acpi_dev_put(adev);
 			dev_err(ADEV_DEV(adev), "Failed to find MEI or CVS CSI dev\n");
+			acpi_dev_put(adev);
 			return -ENODEV;
 		}