[PATCH v1] mtip32xx: fix use-after-free on service thread failure

[PATCH v1] mtip32xx: fix use-after-free on service thread failure

[Yuho Choi]

If service thread creation fails after device_add_disk() succeeds,
mtip_block_initialize() calls del_gendisk() and then falls through to
put_disk(). Since mtip32xx uses .free_disk to free struct driver_data,
put_disk() can release dd on the added-disk path.

The same unwind then continues to use dd for blk_mq_free_tag_set() and
mtip_hw_exit(), and mtip_pci_probe() can later free dd again. This can
cause a use-after-free and double free.

Track whether the disk was added in the current initialization call.
For the post-add service-thread failure path, remove the disk, release
the local hardware resources, and return without dropping the final disk
reference. The probe error path can then finish its cleanup and call
put_disk() after it is done using dd. Keep the pre-add path using
put_disk() before blk_mq_free_tag_set(), and clear dd->disk so the outer
probe cleanup frees dd directly.

Fixes: e8b58ef09e84 ("mtip32xx: fix device removal")
Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
---
 drivers/block/mtip32xx/mtip32xx.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 567192e371a8..ccf5c164cf46 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -3405,6 +3405,7 @@ static int mtip_block_initialize(struct driver_data *dd)
 		.max_segment_size	= 0x400000,
 	};
 	int rv = 0, wait_for_rebuild = 0;
+	bool disk_added = false;
 	sector_t capacity;
 	unsigned int index = 0;
 
@@ -3438,6 +3439,7 @@ static int mtip_block_initialize(struct driver_data *dd)
 		dev_err(&dd->pdev->dev,
 			"Unable to allocate request queue\n");
 		rv = -ENOMEM;
+		dd->disk = NULL;
 		goto block_queue_alloc_init_error;
 	}
 	dd->queue		= dd->disk->queue;
@@ -3496,6 +3498,7 @@ static int mtip_block_initialize(struct driver_data *dd)
 	rv = device_add_disk(&dd->pdev->dev, dd->disk, mtip_disk_attr_groups);
 	if (rv)
 		goto read_capacity_error;
+	disk_added = true;
 
 	if (dd->mtip_svc_handler) {
 		set_bit(MTIP_DDF_INIT_DONE_BIT, &dd->dd_flag);
@@ -3511,7 +3514,9 @@ static int mtip_block_initialize(struct driver_data *dd)
 		dev_err(&dd->pdev->dev, "service thread failed to start\n");
 		dd->mtip_svc_handler = NULL;
 		rv = -EFAULT;
-		goto kthread_run_error;
+		if (disk_added)
+			goto kthread_run_error;
+		goto read_capacity_error;
 	}
 	wake_up_process(dd->mtip_svc_handler);
 	if (wait_for_rebuild == MTIP_FTL_REBUILD_MAGIC)
@@ -3522,6 +3527,10 @@ static int mtip_block_initialize(struct driver_data *dd)
 kthread_run_error:
 	/* Delete our gendisk. This also removes the device from /dev */
 	del_gendisk(dd->disk);
+	mtip_hw_debugfs_exit(dd);
+	blk_mq_free_tag_set(&dd->tags);
+	mtip_hw_exit(dd);
+	return rv;
 read_capacity_error:
 init_hw_cmds_error:
 	mtip_hw_debugfs_exit(dd);
@@ -3529,6 +3538,7 @@ static int mtip_block_initialize(struct driver_data *dd)
 	ida_free(&rssd_index_ida, index);
 ida_get_error:
 	put_disk(dd->disk);
+	dd->disk = NULL;
 block_queue_alloc_init_error:
 	blk_mq_free_tag_set(&dd->tags);
 block_queue_alloc_tag_error:
@@ -3839,7 +3849,10 @@ static int mtip_pci_probe(struct pci_dev *pdev,
 	}
 
 iomap_err:
-	kfree(dd);
+	if (dd->disk)
+		put_disk(dd->disk);
+	else
+		kfree(dd);
 	pci_set_drvdata(pdev, NULL);
 	return rv;
 done:
-- 
2.43.0

Re: [PATCH v1] mtip32xx: fix use-after-free on service thread failure

[Jens Axboe]

On Mon, 25 May 2026 12:25:31 -0400, Yuho Choi wrote:
> If service thread creation fails after device_add_disk() succeeds,
> mtip_block_initialize() calls del_gendisk() and then falls through to
> put_disk(). Since mtip32xx uses .free_disk to free struct driver_data,
> put_disk() can release dd on the added-disk path.
> 
> The same unwind then continues to use dd for blk_mq_free_tag_set() and
> mtip_hw_exit(), and mtip_pci_probe() can later free dd again. This can
> cause a use-after-free and double free.
> 
> [...]

Applied, thanks!

[1/1] mtip32xx: fix use-after-free on service thread failure
      commit: 6b24446bee489e90f7ea843fbc0473393c73cbf9

Best regards,
-- 
Jens Axboe