[PATCH 6.1 098/312] media: mc, v4l2: serialize REINIT and REQBUFS with req_queue_mutex

Greg Kroah-Hartman
2026-04-08T18:11:03Z

From: Yuchan Nam <entropy1110@gmail.com>

commit bef4f4a88b73e4cc550d25f665b8a9952af22773 upstream.

MEDIA_REQUEST_IOC_REINIT can run concurrently with VIDIOC_REQBUFS(0)
queue teardown paths. This can race request object cleanup against vb2
queue cancellation and lead to use-after-free reports.

We already serialize request queueing against STREAMON/OFF with
req_queue_mutex. Extend that serialization to REQBUFS, and also take
the same mutex in media_request_ioctl_reinit() so REINIT is in the
same exclusion domain.

This keeps request cleanup and queue cancellation from running in
parallel for request-capable devices.

Fixes: 6093d3002eab ("media: vb2: keep a reference to the request until dqbuf")
Cc: stable@vger.kernel.org
Signed-off-by: Yuchan Nam <entropy1110@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/media/mc/mc-request.c | 5 +++++
drivers/media/v4l2-core/v4l2-ioctl.c | 5 +++--
2 files changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/media/mc/mc-request.c
+++ b/drivers/media/mc/mc-request.c
@@ -190,6 +190,8 @@ static long media_request_ioctl_reinit(s
struct media_device *mdev = req->mdev;
unsigned long flags;

+ mutex_lock(&mdev->req_queue_mutex);
+
spin_lock_irqsave(&req->lock, flags);
if (req->state != MEDIA_REQUEST_STATE_IDLE &&
req->state != MEDIA_REQUEST_STATE_COMPLETE) {
@@ -197,6 +199,7 @@ static long media_request_ioctl_reinit(s
"request: %s not in idle or complete state, cannot reinit\n",
req->debug_str);
spin_unlock_irqrestore(&req->lock, flags);
+ mutex_unlock(&mdev->req_queue_mutex);
return -EBUSY;
}
if (req->access_count) {
@@ -204,6 +207,7 @@ static long media_request_ioctl_reinit(s
"request: %s is being accessed, cannot reinit\n",
req->debug_str);
spin_unlock_irqrestore(&req->lock, flags);
+ mutex_unlock(&mdev->req_queue_mutex);
return -EBUSY;
}
req->state = MEDIA_REQUEST_STATE_CLEANING;
@@ -214,6 +218,7 @@ static long media_request_ioctl_reinit(s
spin_lock_irqsave(&req->lock, flags);
req->state = MEDIA_REQUEST_STATE_IDLE;
spin_unlock_irqrestore(&req->lock, flags);
+ mutex_unlock(&mdev->req_queue_mutex);

return 0;
}
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -2987,13 +2987,14 @@ static long __video_do_ioctl(struct file
vfh = file->private_data;

/*
- * We need to serialize streamon/off with queueing new requests.
+ * We need to serialize streamon/off/reqbufs with queueing new requests.
* These ioctls may trigger the cancellation of a streaming
* operation, and that should not be mixed with queueing a new
* request at the same time.
*/
if (v4l2_device_supports_requests(vfd->v4l2_dev) &&
- (cmd == VIDIOC_STREAMON || cmd == VIDIOC_STREAMOFF)) {
+ (cmd == VIDIOC_STREAMON || cmd == VIDIOC_STREAMOFF ||
+ cmd == VIDIOC_REQBUFS)) {
req_queue_lock = &vfd->v4l2_dev->mdev->req_queue_mutex;

if (mutex_lock_interruptible(req_queue_lock))