[PATCH v1 4/6] dmaengine: ioat: disable relaxed ordering before registering the device

[Logan Gunthorpe]

ioat3_dma_probe() disabled PCIe relaxed ordering after calling
dma_async_device_register(), so if an error occurs and the code jumps
to err_disable_interrupts, the function returns with the device still
registered in the core's dma_device_list while the caller frees the
ioatdma_device struct, leaving a dangling registration that anything
walking the device list can dereference after it's been freed.

Move the capability read/write ahead of dma_async_device_register()
instead. Nothing after registration depends on relaxed ordering
already being disabled, and nothing before it depends on the device
being registered, so this is a plain reordering. It also means every
remaining step after registration can't fail, so there's no need to
ever have to unregister the device once registered.

Fixes: 511deae0261c ("dmaengine: ioatdma: disable relaxed ordering for ioatdma")
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Link: https://lore.kernel.org/dmaengine/20260707165906.249F41F000E9@xxxxxxxxxxxxxxx/T/#u
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
 drivers/dma/ioat/init.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/dma/ioat/init.c b/drivers/dma/ioat/init.c
index 737496391109..a57024c4b066 100644
--- a/drivers/dma/ioat/init.c
+++ b/drivers/dma/ioat/init.c
@@ -1170,15 +1170,6 @@ static int ioat3_dma_probe(struct ioatdma_device *ioat_dma, int dca)
 		       ioat_chan->reg_base + IOAT_DCACTRL_OFFSET);
 	}
 
-	err = dma_async_device_register(&ioat_dma->dma_dev);
-	if (err)
-		goto err_disable_interrupts;
-
-	ioat_kobject_add(ioat_dma, &ioat_ktype);
-
-	if (dca)
-		ioat_dma->dca = ioat_dca_init(pdev, ioat_dma->reg_base);
-
 	/* disable relaxed ordering */
 	err = pcie_capability_read_word(pdev, PCI_EXP_DEVCTL, &val16);
 	if (err) {
@@ -1194,6 +1185,15 @@ static int ioat3_dma_probe(struct ioatdma_device *ioat_dma, int dca)
 		goto err_disable_interrupts;
 	}
 
+	err = dma_async_device_register(&ioat_dma->dma_dev);
+	if (err)
+		goto err_disable_interrupts;
+
+	ioat_kobject_add(ioat_dma, &ioat_ktype);
+
+	if (dca)
+		ioat_dma->dca = ioat_dca_init(pdev, ioat_dma->reg_base);
+
 	if (ioat_dma->cap & IOAT_CAP_DPS)
 		writeb(ioat_pending_level + 1,
 		       ioat_dma->reg_base + IOAT_PREFETCH_LIMIT_OFFSET);
-- 
2.47.3