[PATCH v2] dmaengine: idxd: fix potential NULL pointer dereference on wq setup error path

[Shuai Xue]

If wq allocation fails during the initial iteration of the loop,
`conf_dev` is still NULL.  However, the existing error handling via
`goto err` would attempt to call `put_device(conf_dev)`, leading to a
NULL pointer dereference.

This issue occurs because there's no dedicated error label for the WQ
allocation failure case, causing it to fall through to an incorrect
error path.

Fix this by introducing a new error label `err_wq`, ensuring that we
only invoke `put_device(conf_dev)` when `conf_dev` is valid.

Fixes: 3fd2f4bc010c ("dmaengine: idxd: fix memory leak in error handling path of idxd_setup_wqs")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Colin King <colin.i.king@xxxxxxxxx>
Closes: https://lore.kernel.org/dmaengine/aDQt3_rZjX-VuHJW@stanley.mountain
Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
---
changes since v1: 
- add Reviewed-by tag from Dave Jiang
- add Reported-by tag from Dan Carpenter and its Closes link
---
 drivers/dma/idxd/init.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 80355d03004d..a818d4799770 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -196,7 +196,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
 		wq = kzalloc_node(sizeof(*wq), GFP_KERNEL, dev_to_node(dev));
 		if (!wq) {
 			rc = -ENOMEM;
-			goto err;
+			goto err_wq;
 		}
 
 		idxd_dev_set_type(&wq->idxd_dev, IDXD_DEV_WQ);
@@ -246,6 +246,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
 	put_device(conf_dev);
 	kfree(wq);
 
+err_wq:
 	while (--i >= 0) {
 		wq = idxd->wqs[i];
 		if (idxd->hw.wq_cap.op_config)
-- 
2.43.5