[PATCH] scsi: imm: fix use-after-free bugs caused by unfinished delayed work

[PATCH] scsi: imm: fix use-after-free bugs caused by unfinished delayed work

[Duoming Zhou]

The delayed work item imm_tq is initialized in imm_attach() and
scheduled via imm_queuecommand() for processing SCSI commands.
When the IMM parallel port SCSI host adapter is detached through
imm_detach(), the imm_struct device instance is deallocated.

However, the delayed work might still be pending or executing
when imm_detach() is called, leading to use-after-free bugs
when the work function imm_interrupt() accesses the already
freed imm_struct memory.

The race condition can occur as follows:

CPU 0(detach thread)   | CPU 1
                       | imm_queuecommand()
                       |   imm_queuecommand_lck()
imm_detach()           |     schedule_delayed_work()
  kfree(dev) //FREE    | imm_interrupt()
                       |   dev = container_of(...) //USE
                           dev-> //USE

Add disable_delayed_work_sync() in imm_detach() to guarantee
proper cancellation of the delayed work item before imm_struct
is deallocated.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
---
 drivers/scsi/imm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/imm.c b/drivers/scsi/imm.c
index 5c602c057798..45b0e33293a5 100644
--- a/drivers/scsi/imm.c
+++ b/drivers/scsi/imm.c
@@ -1260,6 +1260,7 @@ static void imm_detach(struct parport *pb)
 	imm_struct *dev;
 	list_for_each_entry(dev, &imm_hosts, list) {
 		if (dev->dev->port == pb) {
+			disable_delayed_work_sync(&dev->imm_tq);
 			list_del_init(&dev->list);
 			scsi_remove_host(dev->host);
 			scsi_host_put(dev->host);
-- 
2.34.1

Re: [PATCH] scsi: imm: fix use-after-free bugs caused by unfinished delayed work

[Martin K. Petersen]

Duoming,

> The delayed work item imm_tq is initialized in imm_attach() and
> scheduled via imm_queuecommand() for processing SCSI commands. When
> the IMM parallel port SCSI host adapter is detached through
> imm_detach(), the imm_struct device instance is deallocated.

Applied to 6.19/scsi-staging, thanks!

-- 
Martin K. Petersen

Re: [PATCH] scsi: imm: fix use-after-free bugs caused by unfinished delayed work

[Martin K. Petersen]

On Tue, 28 Oct 2025 18:01:49 +0800, Duoming Zhou wrote:

> The delayed work item imm_tq is initialized in imm_attach() and
> scheduled via imm_queuecommand() for processing SCSI commands.
> When the IMM parallel port SCSI host adapter is detached through
> imm_detach(), the imm_struct device instance is deallocated.
> 
> However, the delayed work might still be pending or executing
> when imm_detach() is called, leading to use-after-free bugs
> when the work function imm_interrupt() accesses the already
> freed imm_struct memory.
> 
> [...]

Applied to 6.19/scsi-queue, thanks!

[1/1] scsi: imm: fix use-after-free bugs caused by unfinished delayed work
      https://git.kernel.org/mkp/scsi/c/ab58153ec64f

-- 
Martin K. Petersen