[PATCH] dmaengine: idxd: add RO check for wq max_transfer_size write

[Dave Jiang <dave.jiang@xxxxxxxxx>]

Block wq_max_transfer_size_store() when the device is configured as
read-only and not configurable.

Fixes: d7aad5550eca ("dmaengine: idxd: add support for configurable max wq xfer size")
Reported-by: Bernice Zhang <bernice.zhang@xxxxxxxxx>
Tested-by: Bernice Zhang <bernice.zhang@xxxxxxxxx>
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
---
 drivers/dma/idxd/sysfs.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
index 7e19ab92b61a..ec13ca4808f9 100644
--- a/drivers/dma/idxd/sysfs.c
+++ b/drivers/dma/idxd/sysfs.c
@@ -905,6 +905,9 @@ static ssize_t wq_max_transfer_size_store(struct device *dev, struct device_attr
 	u64 xfer_size;
 	int rc;
 
+	if (!test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags))
+		return -EPERM;
+
 	if (wq->state != IDXD_WQ_DISABLED)
 		return -EPERM;