dmaengine: idxd: fix fdev setup failure cleanup in idxd_cdev_open()

The failed_dev_add and failed_dev_name paths drop the file-device
reference while wq->wq_lock is still held. If put_device(fdev) drops the
last reference, idxd_file_dev_release() runs synchronously and tries to
take wq->wq_lock again, deadlocking.

Those paths also fall through into the later ctx cleanup labels even
though idxd_file_dev_release() owns that cleanup and frees ctx. This can
make idxd_xa_pasid_remove(ctx) and kfree(ctx) operate on a freed context.

Move idxd_wq_get() before file-device setup can fail, since the release
callback always calls idxd_wq_put(). Then unlock wq->wq_lock before
put_device(fdev) and return directly from the file-device setup failure
path, leaving ctx cleanup to the release callback.

Fixes: e6fd6d7e5f0fe ("dmaengine: idxd: add a device to represent the file opened")
Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260525141550.1385581-1-dbgh9129@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
index 0366c7cf35020f4432db27bae51e41436d8c2e57..82b07cf942ef8255256cf824d34bf7f03d7d96d3 100644 (file)
--- a/drivers/dma/idxd/cdev.c
+++ b/drivers/dma/idxd/cdev.c
@@ -288,6 +288,7 @@ static int idxd_cdev_open(struct inode *inode, struct file *filp)
        fdev->parent = cdev_dev(idxd_cdev);
        fdev->bus = &dsa_bus_type;
        fdev->type = &idxd_cdev_file_type;
+       idxd_wq_get(wq);
 
        rc = dev_set_name(fdev, "file%d", ctx->id);
        if (rc < 0) {
@@ -301,13 +302,14 @@ static int idxd_cdev_open(struct inode *inode, struct file *filp)
                goto failed_dev_add;
        }
 
-       idxd_wq_get(wq);
        mutex_unlock(&wq->wq_lock);
        return 0;
 
 failed_dev_add:
 failed_dev_name:
+       mutex_unlock(&wq->wq_lock);
        put_device(fdev);
+       return rc;
 failed_ida:
 failed_set_pasid:
        if (device_user_pasid_enabled(idxd))